Thursday, 20 November 2014

4 Transistor 500mW FM Transmitter Circuit Diagram

44 Transistor 500mW FM Transmitter Circuit Diagram

As shown, the audio ascribe is a microphone, which uses 2 x 2N3904 as the microphone audio preamplifier. The audio/mic ascribe akin is adjustable by agency of a 5k preset / potentiometer.

The ambit uses a Colpitts oscillator for abundance generation, which is chargeless active and operates at the axiological abundance i.e. no circuitous abundance multiplication or control. The abundance affability basic of the ambit consists of 2 5pF (picoFarad) capacitors and a distinct 10uH (micro-Henry) inductor. These apparatus can be adapted if a change in abundance is appropriate - conceivably alike replaced with capricious capacitors (if youre up to the challenge).

An achievement RF amplifier takes the abundance produced by the Colpitts oscillator and amplifier to about about the 500mW (0.5 Watt) ambit - so this is the almost achievement ability of this FM transmitter. You are brash that back this transmitter operates at the axiological frequency, and because there is no achievement filter, there is acceptable to be some abundance alluvion and harmonics/spurious emissions.

Class B audio amplifier based on TDA1553


Here is the circuit of a Class B audio amplifier based on TDA1553. TDA1553 is a monolithic audio amplifier class B, containing 2 x 22 watt amplifier in bridge configuration load attached. The amplifier operates from 12V DC and develops intentionaly for car audio applications. The IC also has a lot of good features such as short circuit protection, protection of the load dump, reverse polarity protection, speaker protection, etc.

In the circuit, C5 and C4 are decoupling capacitors C3 input, while setting the delay for speaker protection. C1 and C2 are filter capacitors of the offer.

Notes :

  • Assemble the circuit on a good quality PCB.
  • Use 12V DC for powering the circuit.
  • The circuit can deliver 22W per channel into 4 ohm speakers.
  • Fit the IC with a proper heat sink.

Auto Sound Systems are Becoming Entertainment Systems

If youve been shopping lately for an auto sound system then I am fairly certain that youve come across several full entertainment systems among those in the running for your audio and entertainment dollars. Vehicles today offer everything from DVD players, individual speakers, headphones (also individually adjustable), and even dual players that will allow one different audio to be played in one section of the vehicle than another. In addition to all of these wonderful and nifty devices are many more devices that are meant to tempt, sway, and convince you to spend even more money on the auto sound system of your dreams. Some of these even offer MP3 players that connect directly to the audio system of your car, truck, or SUV.

The jury is still out for many people about the safety and sense of having a DVD player in your automobile. While this is the case, people will continue purchasing DVD players are part and parcel of their sound and entertainment systems and manufacturers will continue putting together attractive packages that offer these devices to consumers while offering incredible bargains on installation. I know that many feel that this is an unnecessary distraction to drivers. Im one of the rare people that feels that in a day of laptops, cell phones, talk radio, fast food, Starbucks coffee, and multitasking, a DVD in the back might be one of the best features that can be added to the car in an effort to minimize distractions coming from the direction of disgruntled passengers in the rear.

I will confess that many people wonder what this has to do with an auto sound system and I can understand that question so please bare with me. One of the features that sound system manufacturers are offering is a feature that allows individual headphones for passengers in the back along with LCD monitors that rest in the back of the head rests so that passengers in the back can both see and hear the DVDs being played without causing a distraction for the driver (either by noise or by means of flashing lights).

The truth of the matter is that having the noise from a DVD player in the back is no worse of a distraction than having disgruntled children competing for your attention from the backseat or listening to audio books as you drive along. I must admit that audio books are one of my current and readily admitted addictions. The problem with those is that on occasion some of the books simply arent meant for young ears. I try to keep my books limited to popular stories that are suitable for children whenever my children are riding along and save the sometimes steamy and often hilarious tales of Stephanie Plum for when Im riding alone. Another great reason to make sure you have an auto sound system that at the very least reads and understands MP3s.

The technology exists for this and I expect to see even more innovations technologically speaking in the way of auto sound systems and entertainment systems in the near and not so near future. We live in a world where technology is constantly evolving and we should see many new and wonderful features that will make our lives much more enjoyable for our daily commute.

Whether you are new to the technology of today, fighting it mightily, or happily embracing it-it isnt showing any signs of stopping or slowing down. This means that you will eventually have to face the fact that the old ways of buying an auto sound system will soon be obsolete. I often joke that we are rapidly becoming a society that is catching up with the "Jetsons" vision for the future. I also loudly lament my lack of a Rosie. At any rate, I am glad to see that the new technologies in auto sound systems are offering less of a one size fits all image and offering much more individual systems, even for passengers within a vehicle.

Wednesday, 19 November 2014

Smart Tracker track anything from your child to shoes

The EPE Minder consists of two type- approved transmitter units and a receiver. If either transmitter becomes separated from the receiver, a buzzer in the latter part will sound.
The receiver is fitted with a switch to allow the use of only one transmitter if required.

MIND HOW YOU GO

This system was originally designed as a two-channel child alarm (to protect either a single child or two children at the same time) but many other applications spring to mind. For example, one transmitter could be placed inside a briefcase and another in a coat pocket. If the user forgot to pick up either of these items and walked away, the buzzer would sound in the receiver. The receiver must be carried on the per- son in a way that would make it practically impossible to lose it. This could be done using a belt clip, for example. Note that it will not be possible to use this system if either the transmitter or receiver were placed inside metal containers or if there were substantial metallic “screening” objects between them.

OPERATING RANGE
The operating range may be adjusted according to the intended purpose. However, it does depend on conditions. Adjustment is carried out by means of “aerial link wires” on the circuit panels. With all these in place, the range of the prototype exceeds 12 metres in open air. It will also work throughout several rooms indoors if required. If the battery voltage in either transmit- ter or receiver falls below a certain value, or if a transmitter is switched off, a buzzer will sound. The specified batteries in the transmitters should provide several hun- dred hours of operation. Those in the receiver should provide around 100 hours.

PERSONAL CODE
The EPE Minder uses a system of digitally encoded low-power radio signals,
which pass from the transmitters to the receiver. The code is different for each transmitter so that the receiver is able to distinguish one from the other. Type-approved, pre-aligned transmitter and receiver modules that operate at 433MHz. are used. No traditional “radio” skills are needed and no licence is needed for their use in the UK.

TRANSMITTER CIRCUIT
The circuit diagram for a single trans- mitter unit is shown in Fig.1. Current is
supplied to the circuit from a 3V “coin” cell, B1, via on-off switch S2 and diode D1. The diode provides reverse-polarity protection. It is best to use the specified Schottky device which introduces a smaller forward voltage drop, and therefore less loss, than a conventional silicon diode (0·2V rather than 0·7V approximately). Capacitor C2 provides a small reserve of energy and pre- vents the supply voltage from fluctuating. This stabilises operation. A low power 7555 timer, IC1, is set up in a standard astable (pulse generator) con- figuration. While switched on, this produces a continuous train of on-off pulses at its output, pin 3.The choice of resistors R1, R2 and capacitor C1 provide one pulse per second for one of the transmitters (Unit A) and one pulse every 1·2 seconds for the other one (Unit B). In fact, the timings are slightly longer but it helps to consider them as above. Also, the on times are much longer than the off ones in each case. The purpose of this will be explained presently.




RECEIVER CIRCUIT

Receiver module, IC1, requires a supply of between 4·5V and 5·5V. The 6V nomi-
nal battery pack, B1, is brought within range by the forward drop of diode D5
(0·7V approx.) This diode also provides reverse-polarity protection. Capacitor C4 charges up and provides a small reserve of energy. This will be useful when the battery is nearing the end of its operating life. When the supply voltage falls below some 4V, the receiver stops working and the buzzer will sound. Below around 3V, the buzzer itself will not operate so it is important to check operation each time the units are used. Receiver IC1 should be of the a.m. (amplitude modulation) type as specified in the components list. As such, it will respond to the on-off pulses provided by the transmitter. The inexpensive super regenerative (rather than superhet) variety will be perfectly adequate. The low-power variants of these receivers have not been tested. Although for battery operation they would appear to be ideal, the standard type is more readily available.

The receiver may be considered as hav- ing separate r.f. (radio frequency) and a.f. (audio frequency) sections. These have individual supply inputs (pins 1, 10, 12 and 15 with some being duplicated). These are all connected together and decoupled using capacitor C1.

TESTING

Having completed the Receiver board, we can now commence testing all three
boards. It helps to minimise the Receiver “hold-off” time by adjusting preset VR1 fully anti-clockwise (as viewed from the left-hand side of the p.c.b.) and preset VR2 fully clockwise (as viewed from the right- hand side of the p.c.b.). Check that the Test link has been left unconnected to prevent IC4b signal from passing to transistor TR1’s base. Switch on Single Channel switch S3 so that Channel A is enabled. With On-Off switch S4 off, insert the batteries. Switch on. After a short delay, the buzzer WD1 should sound. Now place Transmitter A approximately
three metres away from the Receiver, insert the battery and switch on. The buzzer should begin to bleep every second. The same procedure is now repeated for Transmitter B. To do this, switch S3 off to disable Channel A and firmly twist together the ends of the Test link wires. It is not advisable to solder this connection unless the i.c.s are removed first. The buzzer should bleep at a slightly slower rate than for Transmitter A. It is unlikely that the time periods of the two transmitters will be the same (due to overlapping component tolerances).
However, if they are, one of them will need to be changed. Choose slightly higher values for resistors R1 and R2 to slow it down and vice versa. Remove the i.c.s before making any modifications.

HOLD-OFF TIME
When both transmitters have been test- ed, switch S3 on to enable both channels. presets VR1 and VR2 should now be adjusted to approximately mid-track posi- tion. This should provide a sufficient “hold off” time plus a small margin. The buzzer should now remain off and only sound when one of the transmitters is switched off or moved out of range. Leave them operating for several minutes. If the occasional spurious bleep is heard, increase the settings of VR1/VR2 to pre- vent this happening.

NE555 IC Timer

The 555 Timer is an integrated circuit (chip) implementing a variety of timer and multivibrator applications. The IC was designed and invented by Hans R. Camenzind. It was designed in 1970 and introduced in 1971 by Signetics (later acquired by Philips). The original name was the SE555/NE555 and was called "The IC Time Machine".


The 555 gets its name from the three 5-k Ohm resistors used in typical early implementations. It is still in wide use, thanks to its ease of use, low price and good stability. As of 2003[update], 1 billion units are manufactured every year.

The 555 timer is one of the most popular and versatile integrated circuits ever produced. It includes 23 transistors, 2 diodes and 16 resistors on a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8).

The 555 has three operating modes:

* Monostable mode: in this mode, the 555 functions as a "one-shot". Applications include timers, missing pulse detection, bouncefree switches, touch switches, Frequency Divider,Capacitance Measurement, Pulse Width Modulation (PWM) etc

* Astable - Free Running mode: the 555 can operate as an oscillator. Uses include LED and lamp flashers, pulse generation, logic clocks, tone generation, security alarms, pulse position modulation, etc.

* Bistable mode or Schmitt trigger: the 555 can operate as a flip-flop, if the DIS pin is not connected and no capacitor is used. Uses include bouncefree latched switches, etc.


The connection of the pins is as follows:
Nr. Name Purpose

1 GND Ground, low level (0V)
2 TR A short pulse high → low on the trigger starts the timer
3 Q During a timing interval, the output stays at +VCC
4 R A timing interval can be interrupted by applying a reset pulse to low (0V)
5 CV Control voltage allows access to the internal voltage divider (2/3 VCC)
6 THR The threshold at which the interval ends (it ends if U.thr → 2/3 VCC)
7 DIS Connected to a capacitor whose discharge time will influence the timing interval
8 V+, VCC The positive supply voltage which must be between 3 and 15 V


In the astable mode, the high time from each pulse is given by

high = 0.693.(R1 + R2).C

and the low time from each pulse is given by

low = 0.693.R2.C

where R1 and R2 are the values of the resistors in ohms and C is the value of the capacitor in farads.


Specifications

These specifications apply to the NE555. Other 555 timers can have better specifications depending on the grade (military, medical, etc).

* Supply voltage (VCC) 4.5 to 15 V
* Supply current (VCC = +5 V) 3 to 6 mA
* Supply current (VCC = +15 V) 10 to 15 mA
* Output current (maximum) 200 mA
* Power dissipation 600 mW
* Operating temperature 0 to 70 °C

AT89C2051 microcontroller circuit

Real time controller AT89C2051
Real time controller is a device used to exercise control over household device continuously ongoing and scheduled. The series of Real Time Controllers with microcontroller AT89C2051 which dituls in this article is a tool that can do that serve targeted. The series of Real Time Controller with Microcontroller AT89C2051 Atmel AT89C2051 uses a data processor and controller as device installed. 


In the application directly devices requires a separate interface from a wide range of Real Time Controllers with this AT89C2051 microcontroller. When will connect the device with the AC power source to use interface optocoupler (MOC) or solid state relay. Devices that can be connected with the series of Real Time Controller with Microcontroller AT89C2051 include lights, water machines, fans, electronic gate. The series of Real Time Controllers with this AT89C2051 microcontroller to control a height of water level, controlling the flame lights the scheduled SCARA and censored.

Specifications Series Real Time Controller with AT89C2051 Microcontroller
The series of Real Time Controller with Microcontroller AT89C2051 uses a computer to perform serial communication settings via computer. The series of Real Time Controller with Microcontroller AT89C2051 has 6 units of output channels that can be independently controlled depending on the program induced in the tool. Output in the series of Real Time Controller with AT89C2051 microcontroller requires an interface to deal with equipment that will be in control.

Tuesday, 18 November 2014

Toggle switch with Infra Red IR

Toggle switch in this article is a series of toggle switches that are controlled by infrared light. The series toggle switch is made from a combination of data flip-flop CD4013 2 units. Receiver circuit of the infrared light signals arranged with infrared receiver as found on television remote receiver. Infrared signal from remote is used as clock signals and data to the data flip-flop first. then the second flip-flop data set as a toggle flip-flop toggle the output signal is used to drive the relay. for more details can be seen in thethe following image .


Toggle


Series Toggle Switch With Infra Red (IR) that is required to supply voltage range of 12VDC and the output of Toggle Switch With Infra Red (IR) is dapt used to turn on the lights or other electronic devices with DC or AC voltage source. Series Toggle Switch With Infra Red (IR) was isolated from the load that is placed for use as the final relay.

4069 Latching Relay Driver



4069 Latching Relay Driver

ADC 207 Flash Converting

Flash Converting - ADC 207
ADC 207 is the first to use Flash Converting An Advanced High Speed ​​VLSI 1.2 micron CMOS process. The process that is able to do the ADC 207 as mentioned earlier is very great and makes the ADC 207 is unique. The speed of the process of this ADC has a good linearity and have a stable temperature. ADC 207 has a lower power consumption is 250 mW.
ADC is working with +5 VDC voltage source and at a frequency of 20 MHz. ADC 207 has a small sampling time is 12nS, thus making the ideal sampling results. ADC 207 has 128 features auto balanced comparators with each conversion that serves to offset temperature and dynamic effects that exist. Resistor ladder in the ADC 207 has a mid point that is connected to an external voltage source and function in the conversion of 7-bit linearity. ADC 207 has 3 levels of output that is easy to connect it with external components.

ADC 207 Architecture

Feature ADC 207

7-bit flash A / D Converter Sampling frequency of 20 MHzLow power consumption (250mW)VCC 5 VDC1.2 micron CMOS technology7 bits with 3 levels of output gates and overflow bits

1000W ICs audio amplifier with PA03

This is a series of amplifiers are based on the most high-ic power that I have ever known. Because the output is issued up to 1000 watts with the impedance RL 4Ohm. Current supply 120mA, and 30A output current. Minimum input voltage of about 30V and a maximum voltage up to 150V. This is an audio amplifier that I have come across use ICs that maximum voltage up to 150V and output power up to 1000W , the scheme below gan.



Part List
Resistor
R1 = 10K
R2 = 10K
R3 = 220K
R4 = 0.18R 5W
R5 = 2.2R 2W
R6 = 0.18R 5W
Capacitor
C1 = 1uF
C2 = 1000uF
C3 = 68pF
C4 = 1000uF
Inductor
L1 = 4MH
IC
U1 = PA03

Monday, 17 November 2014

Transceiver Homebrew QRP SSB 80M Band

Radio communication transceiver is a radio transmitter at the same time the plane doubles as a radio receiver used for communication purposes.
It consists of the transmitter and the receiver are assembled in an integrated way. In mulamula generation, the transmitter or receiver or transmitter and receiver sections are assembled separately and is part of a stand sendirisendiri and can work well sendirisendiri Currently employed both parts are integrated in turn.
Transceiver


Aircraft simple transmitter consists of an oscillator generating radio vibration and this vibration after vibration boarded with our voice, in a technique called dimodulir radio, then by the antenna is converted into radio waves and transmitted. As we know that the sound waves we can not reach long distances, although its power is quite large, while the radio waves with a relatively small force can reach a distance of thousands of kilometers. In order for our voice can reach a far distance, then our voice superimposed on radio wave radio results from the vibration generator, called a carrier wave or carrier and the carrier wave was going to deliver our voice to distant places.

In a place far earlier, the radio waves emitted by the antenna received our speaker. By the antenna, radio waves had, in the form of electromagnetic waves is converted into electrical vibrations and into the receiver.

In our speaker receiver plane, vibration and vibration carriernya then discarded and then raised our voices be accommodated through the speakers. With this technique it is possible modilasi an audio vibrations reach a far range.

We sound vibrations enter the transmitter through a microphone, microphone output was often needs to be strengthened first with an audio amplifier is called a microphone preamplifier can be superimposed on the carrier for the modulator.

To increase the transmission power of a transmitter, vibration of the oscillator was before the emitted amplified first with a radio frequncy amplifier. Strengthening can be done once and can also be done more than once. Transmitter is not reinforced is called a level transmitter and the reinforced one called two-level and beyond. In general, to reach 100 Watt transmit power need to strengthen the 3 times, the first amplifier is called predriver, the next amplifier called the driver and final amplifier called the final amplifier.

Block Diagram of SSB Transceiver

If were talking about the Single Side Band, then we touched more on amplitude modulation (AM). At each modulation we do we actually do the mixing between the radio frequency to audio frequency. Any mixing of two frequencies will occur the second summation process and at the same frequency reduction process occurs from both frequencies.

So every time we memodulir carrier, will produce two frequencies at once. For example, a carrier with a frequency of 3000 Kc we modulir with audio ferkuensi 3 Kc, the result is 3003 Kc and Kc 2997, or said occurred two sides of the band is the upper side and lower side. The top side and bottom side are shaped symetris, so if it is a direct result of modulation we mean we memancarakan exude the same two goods.



If we shine the way mentioned above, we use the mode is said to Double Side Band (DSB) because the carrier that includes top and bottom sides are emitted together. In factory-made plane, this mode is usually coded in terms actual AM radio is the DSB technique.

We know there are two kinds of ways to make the SSB, the first way is by phase shift method, another way is by filtering methods. The first way is not widely used and factory-made aircraft SSB generally use filtering.

Signal DSBSC, before the amplified and transmitted, is inserted into the SSB filter in advance to produce LSB or USB. Filters are used for this purpose is filtering crystal or mechanical filters. SSB transmitter is said to be more efficient than AM (DSB), we can give this picture as follows. For example transmitter AM (DSB) with power 150 Watt (100% modulation depth), then power on the USB and LSB respectively and the carrier has a 25 Watt 100 Watt power. We know that the audio side we are on the band. In the SSB emission, emitted only one side band LSB or USB is a powernya only 25 Watt.
With SSB 25 Watt beam, the audio we have to arrive at destination with the same clarity of information with jet AM (DSB) 150 Watt earlier.

Another advantage of SSB is the wide-band mode that can be more narrow. For the purposes of communication, SSB mode requires only the band width of about 3 Kc, while the DSB mode takes about 6 Kc, thus providing savings SSB mode the use of the band.

In the detector a SSB receiver, the received signal must be mixed in advance with the frequency of the outcome of a Beat Frequency Oscillator (BFO) and used as the BFO carrier oscillator.

Homebrew QRP SSB Transceiver circuit 80m Band

In general, the transceiver has the following block diagram, basically Transceiver tebagi into three main parts: Part VFO and BFO Part Transmitter (transmitter) and Section Receiver (receiver), where there are some special blocks that are used for both paths are either transmitter or receiver. Simply in this transceiver merkit Use the tools that we only Multi tester, RF Probe, SWR and Power Meter, Tone Generator Af 1Kc and multi-band Radio HF SSB to function as a monitor frequency BFO, VFO, monitor Balanced Modulator Exciter at once both the transmitter or receivers .

Data Transceiver:
Frekwency Range: 3700 Kc a / d 3900 Kc
Mode: LSB Singgle conversi
IF: 455 Kc (Ceramic Filter SFU type 455)
Local oscillator: VFO with Fine Tuning varactor diode
BFO: Ceramic Filter 455 SFU
RF PA: Power FET IRF640, IRF540, IRFZ44
DC: 13.8 V
RF Power: Over 8Watt

Description Schema.
The order of assembly sequence of assembling consecutive start BFO, VFO, AF Amp, IF amplifier and detector products to filter amplifier circuit, Mic Amplifier, Balanced modulator, RX mixer + Rf amplifier, mixer TX last order to facilitate the checking of each unit due to series This is a merger of several units of its own circuit.

BFO.

Using SFU type ceramic filters used 455 two-foot middle leg to ground is coupled with capacitor and capacitor trimer and one leg edges to the base of the transistor, BFO uses two types of 2SC1815 transistors. Tc 1 to set the BFO on 453.5Kc frekwensy being black 455Kc IF transformer to regulate the level rather than BFO. To check this The set uses RF Probe. At the secondary BFO output T9 check with RF probe set T9 smpai maximum output level monitor in the radio frequency or HF trimer and Counter set Capacitor capacitor pararelnya until fulfilled the required frequency of 453.5Kc. To check whether there are oscillations in the BFO off Ceramik filter whether RF probe was still moving when he checks it again rangakain ceramik here if we filter out the RF probe is not moving.

VFO.

For we use the VFO FET 2SK192 Type and reinforced with a single fruit type transistor 2SC1815. Raft of this series as neat munkin with component selection, especially capacitor here we use a paper capacitor in series of Colpits oscillator. Close this series with a metal box along with all Varconya. VFO same testing with the BFO circuit Trime Koker Ferrite T13 dapakan frequency monitor the frequency of 4100 Kc s / d 4300 Kc obtained in case of no frequency range is set set the number of coil and capacitor values ​​bypas to groundnya.

AF amplifier.
AF Amplifier IC type LM386 used raft this section and check out by Spiker at putnya. Plug the foot of its inputs with a screwdriver had no defects at the time vulume potensio enlarged.

IF AMP AND PRODUCT detector.

Raft had Produc detectornya from starting until the fourth diode 1N60 IF transformer T7 455 black color until the transformer bypass capacitor to ground. Plug one side of the transformer with a screwdriver kai harden the audio volume on the speakers should be no reaction. Attach the amplifier transistor for testing at its base on the speaker should be louder voice. Raft this section everything.

FILTER amplifier.
Put all the components properly to eighth ceramic filter installed all. Just listen to the speaker plug on the input or pairs if a small number of meters of cable serves as an antenna trim T6 and T8 listen to the voice on the speaker until no defects dispeaker be hissed loudly.

RX MIXER AND RF amplifiers.
This series of rafts with the good and right in making the winding must be in a state of neat. Enter Snyal VFO to try to monitor the input mixer is QSO friends turn ferrite in successive Koker turu of T3 and T4 to get a strong signal reception and set the T1 and T2 ferrite to signal strong receipts received with respect to the level of the S Meter. If that is not found try to check this section further. Thus selesei weve Section Receiver unit.

MIC amplifier. Raft of this section and replace all the LM 741 IC listen with headphones turn out putnya potensio putnya try out the level of talk in the microphone must be perfect without any defects in the out putnya.

BALANCE modulator.
Balanced modulator uses AN612 ic type commonly used on the CB radio. Raft all components correctly. To check this series of pairs of probes to the output at ic AN612 when no signal on the IC probe set trimpot until the deviation of zero and then try to plug in with tweezers pda mic input amplifier should have needle probe deviation. Then plug micropon try talking meter on the probe to move the motion according to your speech input level. Put some small cable length as the antenna you are trying to monitor diradio HF signal here was DSB Uper and Lower Side band sound. Dengarka until there is no defect here is selesei sets. Then go Filter amplifier output to try to talk Rangkian denagan put up some yards kabbel to secondary T6 try IF 455 White color monitor frequency of 455 Kc diradio on and try to talk trim ferrite Ferrite T6 and T8 until you hear the sound on USB diradio no oscillation and no deviation selef the meter on the probe.


TX MIXER.
Raft section make this all too well circumference at T11 and T12 as neat as possible. Mixer that we use the type of premises IC TA7310 2SC1815 transistor amplifier pairs as well. Then plug VFO output and Out put Balnce Modulatornya on laulu TA7310 ic input probe pairs give the mic input with tone generator af ferrite trim T11 and T12 refer to deviation meter probe to obtain the largest deviation meter. Put microppon try talking dimicropon deviation meter see if were not talking micropon but no deviation on the meter needle probe set trim T11 and T12 until no deviation in meters try to talk again in micropon deviation meter should move according to their level talks on the microphone. Try installing a few meters of the small wires on the monitor amplifier output tx diradio exciter in accordance with the frequency of our work with the fashion side band LSB if we do not get on the LSB mode with sempurana set again trimer capacitor on the BFO and rotate slightly if T8 transformer ferrite in black color smpai obtained side band we want. Up here seleseilah exciter circuit.

TX PA amplifier.

PA series we take the type of Power FET because it is cheap and easily available in the market. Create a transformer with a good and right not to email pda scuffed pair of wires until there is a first level transistor 2SC1815 output pairs of probes on trying to talk on the microphone deviation at Beh probe must be greater than the level of exciter here should not happen if not self-oscillation oscillation talk there is no deviation on the meter needle probe. In the event of self-oscillation try to check the part. Similarly, the driver assembly. Drivers are taking transistor type 2 SC1162. gained power level meter must be greater than the previous level as well. Then the final units also make coils as neat as possible. Testing out first input of the exciter arur Pa measuring voltage trimpot should not exceed 3V plug out put a probe hyarus no deviation on the meter. In the event of significant deviation occurs in pagian the oscilasi cell. Then plug the input of the exciter ac voltmeter pairs of avo meter try to speak in micropon meter on ac at avo meter should show a few volts ac in accordance with the level of talking on the microphone.

LOW PASS FILTER.

Create a winding low pass filter with a nice and neat L1 and L2. pairs of all components of the relay to properly check penyambunngan pairs dumy 50 Ohm load at the antenna output connector do not forget to SWR and Power meter is installed. Speaking at a microphone set set ferrite Koker L1 and L2 to obtain the maximum and then check SWR poiwer it must appoint 1: 1 with dumy Load 50 ohms if not check again Low Pass filters. After iti try to plug the 80m band antenna connector is on your monitor qrp radio QSO friends who try to enter it and asked for the report

100W Audio Amplifier with TDA7294

TDA7294 is an integrated, monolithic, Class AB audio amplifier designed precisely for Hi-Fi applications. The IC has a DMOS output stage and can deliver 100W RMS into an 8Ohm speaker at +/-38V dual supply.

In the circuit TDA7294 is configured to provide 100W output power into an 8Ohm loudspeaker at +/- 38V supply. C8 is the input coupling capacitor and the input is applied to the non-inverting input (Pin3) of the IC. C3 and C9 are power supply filter capacitors although C10 and C4 are bypass capacitors. C2 is the bootstrap capacitor.

RC network comprising of R1 and C1 improves the high frequency stability of the amplifier and as well prevents oscillations. R2 and C6 sets the mute time constant while R3 and C5 sets the standby time constant. S1 the mute switch and S2 are the standby switch. R5 is the input resistance and the amplifiers input impedance has a direct relationship to its value. R4 and R6 is employed for setting type closed loop gain and With the used value, gain is 30dB. C2 is a DC decoupling.

18W Amplifier Schematic Circuit

18W
18W Amplifier Schematic Circuit Part List

P1_____________22K Log. Potentiometer (Dual-gang for stereo)

R1______________1K 1/4W Resistor
R2______________4K7 1/4W Resistor
R3____________100R 1/4W Resistor
R4______________4K7 1/4W Resistor
R5_____________82K 1/4W Resistor
R6_____________10R 1/2W Resistor
R7_______________R22 4W Resistor (wirewound)
R8______________1K 1/2W Trimmer Cermet (optional)

C1____________470nF 63V Polyester Capacitor
C2,C5_________100µF 3V Tantalum bead Capacitors
C3,C4_________470µF 25V Electrolytic Capacitors
C6____________100nF 63V Polyester Capacitor

D1___________1N4148 75V 150mA Diode

IC1________TLE2141C Low noise, high voltage, high slew-rate Op-amp
Q1____________BC182 50V 100mA NPN Transistor
Q2____________BC212 50V 100mA PNP Transistor
Q3___________TIP42A 60V 6A PNP Transistor
Q4___________TIP41A 60V 6A NPN Transistor

J1______________RCA audio input socket

Power supply parts:

R9______________2K2 1/4W Resistor

C7,C8________4700µF 25V Electrolytic Capacitors

D2_____________100V 4A Diode bridge
D3_____________5mm. Red LED

T1_____________220V Primary, 15 + 15V Secondary, 50VA Mains transformer

PL1____________Male Mains plug

SW1____________SPST Mains switch

Speed Fan Control Circuit using IC CD4017B

SpeedSpeed Fan Control Circuit using IC CD4017B Circuit

The simple abstraction activity is use IC CD4017 to ascendancy 4 relays which affix anniversary pole. IC CD4017B which is counter-cum-1kHz decoder and the arresting is disconnected into ten according intervals, Which can be programmed, via the distinct location, 10-mode.

According to the backward advertisement of the continuance of the acting period, the agnate achievement of the CD4017 inhibits adverse CD4017 (per pole of circling and diode D6), and fires the triac.

Here transistor T2 acts as a disciplinarian transistor. Pin by 4017, with aught at the achievement of the sensor for the about-face to 0(zero ascertain output) anniversary canyon through zero.

Remark. The accepted beachcomber forms of assertive positions of the rotary switch, as declared in EFY Lab are in the account 1.

The ambit is able to administer for a ambassador in the activity lighting equipment, hot air, oven singal Universal AC motor, heating, etc.

Sunday, 16 November 2014

Fire Alarm LDR

Fire alarm can be made with a light sensor (LDR) as in the article with the title of Fire Alarm with this LDR sensor. Principles of fire detection Fire Alarm with LDR sensor is to detect the presence of smoke through the LDR. LDR in the series Fire Alarm does not stand alone in detecting a fire, but the LDR in the pair with the light shining on the LDR. Hence, in the detected smoke from the fire then the intensity of light received by the LDR LDR decreases and eventually trigger an alarm system on a series of Fire Alarm with this LDR sensor. Part 2 that in the series of Fire Alarm with Sensor LDR are some of the sensors, tone generator, audio power.




Function Section of the Fire Alarm with Sensor LDR
Part of LDR and light sensor facing to fire smoke detection
Part trigger using transistors and regulators as a trigger tone generator 7805
Tone generator section with IC UM66
Power audio section uses an audio power IC TDA 2002 which is equipped with voleme control (R3)

Friday, 14 November 2014

OBSTACLE AVOIDING ROBOT

This is a simple obstacle avoiding robot with two wheels that can be fabricated using a handful of generally available and inexpensive discrete components. The robot can perform avoidance manoeuvres whenever it detects an obstruction in its path. The electronic part is simple and can be built on a small piece of prototyping board. Although not terribly complicated, the mechanics do require a little care all the same. ROBBOT can be operate by a 6V (1.5x 4) battery pack.

Circuit Diagram



Working

ROBOT uses a front facing Infrared LED (Tx) to scan its path and a Photodiode (Rx) to detect light reverted from the obstacle by reflection. As soos as an obstruction is detected, ROBOT goes into reverse direction, and set off the locomotion in another forward direction. The sensor electronics is wired around the small Op-Amp LM358N (IC1), which is an 8-pin chip having two inbuilt Op-Amps. One part of IC1 used here is configured in comparator mode. The sensitivity of the circuit is controlled by the reference voltage at pin 2 of IC1 using a 10K trimpot (P1). P1 will help to reduce unwanted detections caused by external light sources.

Parts list

Robot Circuit Parts
IC1    : LM358N
T1     : BC547
D1,D2  : 1N4007
LED1   : Green 5mm
Tx     : Infrared LED 3mm
Rx     : Photodiode 3mm
RL1    : 6V/DPDT Relay (also tested with a 5V Relay from O/E/N)
M1,M2  : DC motors (Single Shaft Plastic Gear Motor)
S1     : On/Off Switch
R1     : 150 Ohm
R2     : 10K
R3     : 120 Ohm
P1     : 10K
C1     : 100uF/16V
C2     : 100nF

Robot Parts
Single Shaft Plastic Gear Motor x 2
Plastic Wheel x 2
Plastic Chassis Board
Plastic Castor Bullet x 2
DC Motor Clamp x 2
4 x AA Battery Compartment/Holder x 1

Important Note

Normally relay RL1 switches the positive and negative supplies to both motors M1 and M2. In case of an obstruction detection, RL1 switches to reverse the polarity of the motor connections. D2 now becomes reverse biased and hence supply to M2 is not available. Now only M1 goes into reverse mode. When RL1 switches back (no obstacle detection) Tiny BOT returns to the initial condition.

FREQUENCY TO VOLTAGE CONVERTER CIRCUIT

A very simple and low cost frequency to voltage converter based on the TC9400 IC from Microchip is shown here. TC9400 can be either wired as a voltage to frequency converter or frequency to voltage converter and it requires minimum external components. The functional blocks inside the TC9400 includes integrator opamp, 3uS delay circuit, one shot circuit, charge discharge control circuit, divide by 2 network and necessary drivers. This circuit finds application in a range of electronic projects like frequency meters, tachometers, speedometers, FM demodulators etc.

Circuit Diagram



In the circuit shown above the TC9400 is wired as a F to V converter that operates from a single supply. The circuit generates an output voltage that is proportional to the input frequency. The input frequency is applied to the pin11 (non inverting input of the internal comparator). In order to trip the comparator the amplitude of the input frequency must be greater than +/-200mV.Below this level the circuit will not work at any situation.

Whenever the input signal to the pin 11 of IC1 crosses zero to the negative direction the output of the internal comparator goes low. The 3uS delay circuit enables the Cref charge/discharge circuit after 3uS and this connects the Cref to the reference voltage and this charges the integrating capacitor Cint a specific amount of voltage. In the single supply operation the reference voltage is the potential difference between pin 2 and 7 of the TC9400. Each time the input frequency wave form crosses zero towards positive direction, the output of the internal comparator goes high and this disables the Cref charge/discharge circuit which creates a short circuit across the Cref leads. The voltage across the integrating capacitor Cint is retained because the only discharge path available is the 1M resistor Rint which is a too high and the voltage across Cint is the output voltage. Resistor Rbiasis used to set the bias current of the IC.

The potential divider network comprising of R6 and R7 makes sure that the input threshold tracks the supply voltage always. The clamp circuit using diode D2 prevents the input from going far negative in order to turn on the internal comparator. In simple words this section of the circuit can be generally termed as a level shifter.

The TC9400 manufacturers claim that it can accept a signal of any frequency at its input. In the practical side, for the proper working of this circuit the positive half of the input signal must have at least 5uS pulse width and for the negative half it must be greater than or equal to 5uS.

For calibration adjust the offset adjust trimpot to obtain 0V at the output with no input frequency applied. If you have a function generator, set frequency input to 10KHz and make adjustments in the value of Cref to get around 2.5 to 3 volts at the output. This calibration is meant for a maximum input frequency of 10KHz.

Important points to remember


  • The circuit can be assembled on a Perfect board or PCB.
  • The circuit can be powered from anything between 10 to 15V DC.
  • R3 can be used for adjusting the offset voltage.
  • In the circuit the inverting input of the internal comparator is referenced to 6.2V by using D1. So the input signals amplitude must be between 4V and the supply voltage (V+).
  • The output voltage is also referenced to 6.2V in this circuit.
  • The output voltage and input frequency of the F to V converter is related using the equation V out = V ref x C ref x F in where V out is the output voltage and F in is the input frequency.
  • TC9400 and TL071  must be mounted on holders.

27MHz Transmitter Receiver Radio Control PCBs and Schematic Diagram


This article provides information about 27 MHz Transmitter-Receiver Radio Control related to its PCB assembly/construction. The picture below shows the schematic diagram of the transmitter using IC TX2B.

You will be explained with the instruction for constructing the PCBs (assembly, tuning, transistors, IC, resistors, capacitors (Disk Ceramic, Metallised Polyester, Electrolytic)) for both transmitter (Inductors, LED, Zener Diode, Crystal) and receiver (Zener Diode, Inductors, Resistors, Transistors) with the part value and specifications listed, and how to wiring up the PCBs for both transmitter and receiver.

Find complete description on 27MHz Transmitter-Receiver Radio Control PCBs and Schematic Diagram in this pdf datasheet application (source: scorpiotechnology.com.au).

Thursday, 13 November 2014

Valve Sound Converter

‘Valve sound’ is not just an anachronism: there are those who remain ardent lovers of the quality of sound produced by a valve amplifier. However, not everyone is inclined to splash out on an expensive valve output stage or complete amplifier with a comparatively low power output. Also, for all their aesthetic qualities, modern valve amplifiers burn up (in the full sense of the word!) quite a few watts even at normal listening volume, and so are not exactly environmentally harmless. This valve sound converter offers a cunning way out of this dilemma. It is a low cost unit that can be easily slipped into the audio chain at a suitable point and it only consumes a modest amount of energy.
A valve sound converter can be constructed using a common-or-garden small-signal amplifier using a readily-available triode. Compared to using a pentode, this simplifies the circuit and, thanks to its less linear characteristic, offers even more valve sound. For stereo use a double triode is ideal. Because only a low gain is required, a type ECC82 (12AU7) is a better choice than alternatives such as the ECC81 (12AT7) or ECC83 (12AX7). This also makes things easier for home brewers only used to working with semiconductors, since we can avoid any difficulties with high voltages, obscure transformers and the like:the amplifier stage uses an anode voltage of only 60 V, which is generated using a small 24 V transformer and a voltage doubler (D3, D4, C4 and C5).
Since the double triode only draws about 2mA at this voltage, a 1 VA or 2 VA transformer will do the job. To avoid ripple on the power supply and hence the generation of hum in the converter, the anode voltage is regulated using Zener diodes D1 and D2, and T1. The same goes for the heater supply: rather than using AC, here we use a DC supply, regulated by IC1. The 9 V transformer needs to be rated at at least 3 VA. As you will see, the actual amplifier circuit is shown only once. Components C1 to C3, R1 to R4, and P1 need to be duplicated for the second channel.
The inset valve symbol in the circuit diagram and the base pinout diagram show how the anode, cathode and grid of the other half of the double triode (V1.B) are connected. Construction should not present any great difficulties. Pay particular attention to screening and cable routing, and to the placing of the transformers to minimise the hum induced by their magnetic fields. Adjust P1 to set the overall gain to 1 (0 dB). The output impedance of 47 kΩ is relatively high, but should be compatible with the inputs of most power amplifiers and preamplifiers.

For a good valve sound, the operating point of the circuit should be set so that the audio output voltage is in the region of a few hundred millivolts up to around 1.5 V. If the valve sound converter is inserted between a preamplifier and the power amplifier, it should be before the volume control potentiometer as otherwise the sound will change significantly depending on the volume. As an example, no modifications are needed to an existing power amplifier if the converter is inserted between the output of a CD player and the input to the amplifier.

2N3904 Transistor datasheet Diagram Circuit Emitter Follower Circuit Diagram

The schematic shown below diagrams the emitter follower circuit using 2N3904, an NPN silicon bipolar junction transistor. In the circuit provided, input signal is applied to the base of the transistor, but the output is taken from the emitter.
Instead of using 2N3904 transistors, this emitter follower circuit uses such parameters: 40V collector to emitter voltage (Vce), 6V emitter to base voltage (Veb), 200mA collector current (Ic), 300mW power dissipation (Pmax), 300Mhz frequency where internal capacitances cause gain to be reduced to unity (fT), 10pF internal emitter-base capacitance (Ceb), and 3pF internal base-collector capacitance (Cbc). 

150W LM12 based audio amplifier circuit with explanation

LM12 operational amplifier can output currents up to 10A. The LM12 in encapsulated in TO-3 with 4 pins, can support up to 800W and has enough internal protections to prevent slacks from over-currents or over-heating.
You can use LM12CL with 30 V maximum voltage or LM12C with 40V maximum.
The L1 coil has 40 turns 1mm copper, coiled over R4. If you use LM12CL it is recomended to have toroidal transformer 2 x 22V. The output must be between 7 and 12A. Filtering capacitors must have at least 20.000 uF.
LM12 must be mounted with screws on a big heatsink (=<1.5 C/W) and electric isolated form the heatsink

LM12 amplifier circuit diagram

LM12 amplifier PCB layout


More audio amplifier circuits…

Wednesday, 12 November 2014

TDA2822 Integrated Amplifier Circuits General

General integrated amplifier circuit external components and need more larger heatsink. This paper presents a simple amplifier circuit, made easy. TDA2822 amplifier integrated circuits used in music players, portable DVD and other audio playback; power is not great but you can satisfy the requirements of the hearing, and the circuit is simple, good sound quality, wide voltage range of characteristics such as the amateur production Small amp better choice.

Circuit as shown in Figure 5-107.TDA2822M amp with an integrated circuit to a BTL, (the use of mono and stereo when two) external components only one resistance and two capacitors, with no heatsink, the playback results were satisfactory.
Selection and installation of components:
IC TDA2822M to 8 feet dual inline package, if available can not buy TDA2822 instead, TDA2822 and TDA2822M the same package, which difference is: TDA2822M from 3 V to 15 V can work, and the maximum operating voltage TDA2822 only 8V. TDA2822 must use the voltage dropped to 8 V below. Numerical informal request R1, 10 k generally choose the carbon film resistors. C1 choice of polyester 0.1 uF capacitor, C2 for 100 uF/16V the electrolytic capacitor.


Figure 5-108 its printed circuit board map.

As a simple circuit, the PCB can be engraved shovel role of the rule of law James Shuimo sandpaper or a small amount of water polishes kraft paper, water wash dry, apply a layer of rosin alcohol solution, stem directly after the solder components to the copper foil surface. Welding good after the inspection correct, then no access to speakers, connected to power, between the positive and negative output voltage should be less than 0.1 V. Connected to speakers, hand-touch input, the speaker should be given greater "Ong" sound. Then try to enter the sound signal. Circuit boards do not have to drilling,


Should be used Note: Because this amp for direct coupling, it can not be with DC input signal components. If a DC input signal components must be input in a series connection of around 4.7-10 uF capacitor separated, otherwise, they will have great DC current flow through speakers, so as fever burned. In practice, if 5-107 plans to conduct appropriate reforms are desirable effect.

To improve the circuit as shown in Figure 5-109.

In use found that the volume opened the largest TDA2822M fever when hot, can give TDA2822M produced a heatsink, generally shown in Figure 5-110. Heatsink can be thick lmm, long 38 mm, width of 25 mm made of aluminum plate. And in the heatsink on the reopening of 5-to 6-10 mm, width l mm the slot, then do along the dotted line into a hot film, "I" shape. When first installed heatsink on the release point in TDA2822M. Click 5-111 (a) use the thin Bangzha to bear. It should be noted that the TDA2822M the pin number written on the side of the heatsink, so as to avoid mistakes when welding. And heatsink, volume open only to the most warm, good cooling effect. This method can also be used for other small integrated circuit heat dissipation. Amp circuit caused by two Walkman stereo power continue, to promote two small speakers, good effect.

You can build on the stereo two-channel input circuit, the use of power when a small point, but has it.

LA3161 based Preamplifier circuit with explanation



Preamplifiers are used to amplify low level signals such as those from mikes, tape heads before they are fed into power amplifiers. Power amplifiers are generally less sensitive. Frequency response also can be suitably trimmed and modified at preamp stage. LA 3161 is one of those widely used in tape decks and amplifiers as a stereo preamplifier.


Block Diagram is shown in Figure. LA 3161 has two low noise preamplifiers with good ripple rejection on chip catering to stereo applications. External part count is low and Single In line (SIL))(Figure 43) package makes mounting easy. Wltile the operating voltage is 9V, the IC can tolerate voltages up to 18V. Typical input resistance is WOK and output resistance is 10K with an open loop gain of78dB. Block diagram of the IC is given below. Input is given at Pin 1 and 8, output is taken at Pin 3 and 6, and negative Feedback is given at Pin 2 and 7. Power is at Pin 5 and Pin 4 is the ground terminal. There is an internal voltage regulator.

Ready made PCBs, even populated PCBs are available using this very useful IC. You can still build one, with a Veroboard provided proper care is taken about the ground returns. It simply means that one should not connect ground terminals of output and input at the same place. This will create serious oscillations and normal hobbyist will be left in the woods. Please read general instructions for working with amplifiers in the end.

Light Sensitive Staircase Switch with Triac


When there is no sufficient light/the reset pin is held low by R14 (4.7K resistor) and the circuit works as it is described in the earlier paragraph. But if there is sufficient light, resistance of LDR goes low and the transistor goes into conduction. Now the reset pin goes high and the circuit cannot work. R16 is the sensitivity adjustment. You may use a different color of LEDs at the emitter of Ql and Q4. You may construct the circuit on a single board and can use it for two different applications with a single IC of CD4013. You can use same application in two different latches or make both the same.

In general ICs do not like bad housekeeping, more so when handling mains voltages. Soldering is straightforward. A piece of Vero board is OK. But if you are mounting triacs on the same board, or separately, it is very important to have enough space between tracks such that high voltage arcs do not jump across. It is good idea to remove alternate tracks and mount triacs. BT136 triacs can easily drive 500 W of power. Suitable heat sink must be firmly fixed for each triac individually. Please respect CD4013, a CMOS IC.

Only two switches are shown as examples. You may add more number of switches for use at a number of different locations.

Please be careful that the entire circuit works off 230 V AC mains. If you wish to have isolation from the mains, use relays instead of triacs and use transformer power supply of 12V full wave. Light sense circuit consisting of Q5 and Q6 can be cleverly added to the relay circuit No.l

Tuesday, 11 November 2014

LM317T based Voltage Regulator with Pass Transistor circuit


Here is the circuit diagram for LM 317 T voltage regulator with pass transistor .

SP LED Flashlight Using Supercapacitor

Bored of joking with capacitors? Then its time for you to maneuver on to super-capacitors. These have huge storage capabilities. during this article you may conclude the way to build atiny low LED flashlight using supercapacitors.

The most disadvantage of capacitors is their giant voltage drop. For this project, a minimum voltage of two volts is needed to light-weight the LED. As a result, the “Joule Thief” style would be incorporated here. Using this, a AA battery is used to light-weight an LED until its fully discharged.
 during this case, a supercapacitor would be taking the place of the battery. Here an LED is employed to perform the operate of a diode. This ensures that theres sufficient voltage across the LED.

 the necessities of the project are listed below:
White LED
Super capacitor (10F, 2.7 V)
Transistor
Torus
1 k ohm resistor
Wires
Breadboard
The torus and therefore the transistor used here comes from an energy-saving lamp HS. Care ought to be taken whereas removing this from the lamp as a breakage may lead to the discharge of the mercury vapors. A lamp load along side a USB port is added to the circuit. This makes it compatible with a computer or a automotive radio.


A couple of precautions got to be taken whereas constructing the circuit. The USB port mustnt be supplied with excess power. The capacitor doesnt stand up to a high voltage and hence a zener diode is connected in parallel to handle the high voltage. The diode protects the capacitor when the voltage exceeds an explicit price.

Sunday, 9 November 2014

Contrast Controller Circuit Diagram For LCDs

The adjustment control for the contrast of an LC-Display is typically a 10-k potentiometer. This works fine, provided that the power supply voltage is constant. If this is not the case (for example, with a battery power supply) then the potentiometer has to be repeatedly adjusted. Very awkward, in other words. The circuit described here offers a solution for this problem. 

The aforementioned potentiometer is intended to maintain a constant current from the contrast connection (usually pin 3 or Vo) to ground. A popular green display with 2x16 characters ‘supplies’ about 200 µA. At a power supply voltage of 5 V there is also an additional current of 500 µA in the potentiometer itself. Not very energy efficient either. Now there is an IC, the LM334, which, with the aid of one resistor, can be made into a constant current source. The circuit presented here ensures that there is a current of 200 µA to ground, independent of the power supply voltage. By substituting a 2.2-k? potentiometer for R1, the current can be adjusted as desired.

Circuit diagram:The value of R1 can be calculated as follows: R1 = 227x10-6 x T / I. Where T is the temperature in Kelvin and I is the current in ampères. In our case this results in:
R1 = 227x10-6 x 293 /
(200x10-6)
R1 = 333R
Note that the current supplied by the LM334 depends on the temperature. This is also true for the current from the display, but it is not strictly necessary to have a linear relationship between these two. Temperature variations of up to 10° will not be a problem however. This circuit results in a power saving of over 25% with an LCD that itself draws a current of 1.2 mA. In a battery powered application this is definitely worth the effort! In addition, the contrast does not need to be adjusted as the battery voltage reduces. When used with LCDs with new technologies such as OLED and PLED it is advisable to carefully test the circuit first to determine if it can be used to adjust the brightness.

Circuit diagram:
Contrast Controller Circuit Diagram For LCDs

The value of R1 can be calculated as follows: R1 = 227x10-6 x T / I. Where T is the temperature in Kelvin and I is the current in ampères. In our case this results in:
  • R1 = 227x10-6 x 293 /
  • (200x10-6)
  • R1 = 333R
Note:
  • The current supplied by the LM334 depends on the temperature. This is also true for the current from the display, but it is not strictly necessary to have a linear relationship between these two. Temperature variations of up to 10° will not be a problem however. This circuit results in a power saving of over 25% with an LCD that itself draws a current of 1.2 mA. In a battery powered application this is definitely worth the effort! In addition, the contrast does not need to be adjusted as the battery voltage reduces. When used with LCDs with new technologies such as OLED and PLED it is advisable to carefully test the circuit first to determine if it can be used to adjust the brightness.

Saturday, 8 November 2014

Motor Turn Stall Detector Circuit Diagram

In single phase AC induction motors, often used in fridges and washing machines, a start winding is used during the starting phase. When the motor has reached a certain speed, this winding is turned off again. The start winding is slightly out of phase to the run winding. The motor will only start turning when the current through this winding is out of phase to that of the run winding. The phase difference is normally provided by placing a capacitor of several µF in series with the start winding. When the motor reaches a minimum speed, a centrifugal switch turns off the start winding. 

The circuit diagram doesn’t show a centrifugal switch; instead it has a triac that is turned on during the staring phase. For clarity, the series capacitor isn’t shown in the diagram. Once the motor turns it will continue to do so as long as it isn’t loaded too much. When it has to drive too heavy a load it will almost certainly stall. A large current starts to flow (as the motor no longer generates a back EMF), which is limited only by the resistance of the winding. This causes the motor to overheat after a certain time and causes permanent damage. It is therefore important to find a way to detect when the motor turns, which happens to be surprisingly easy. When the motor is turning and the start winding is not used, the rotation induces a voltage in this winding.

Circuit diagram:
Motor
Motor Turn Stall Detector Circuit Diagram

This voltage will be out of phase since the winding is in a different position to the run winding. When the motor stops turning this voltage is no longer affected and will be in phase with the mains voltage. The graph shows some of the relevant waveforms. More information can be found in the application note for the AN2149 made by Motorola, which can be downloaded from their website at www.motorola.com. We think this contains some useful ideas, but keep in mind that the circuit shown is only partially completed. As it stands, it certainly can’t be put straight to use.

Intelligent Presence Simulator

However effective a domestic alarm system may be, it’s invariably better if it never goes off, and the best way to ensure this is to make potential burglars think the premises are occupied. Indeed, unless you own old masters or objects of great value likely to attract ‘professional’ burglars, it has to be acknowledged that the majority of burglaries are committed by ‘petty’ thieves who are going to be looking more than anything else for simplicity and will prefer to break into homes whose occupants are away.

Rather than simply not going on holiday – which is also one solution to the problem (!) – we’re going to suggest building this intelligent presence simulator which ought to put potential burglars off, even if your home is subjected to close scrutiny. Like all its counterparts, the proposed circuit turns one or more lights on and off when the ambient light falls, but while many devices are content to generate fixed timings, this one works using randomly variable durations.

Circuit diagram:
 intelligent-presence-simulator-circuit-diagramw
Intelligent Presence Simulator Circuit Diagram

So while other devices are very soon caught out simply by daily observation (often from a car) because of their too-perfect regularity, this one is much more credible due to the fact that its operating times are irregular. The circuit is very simple, as we have employed a microcontroller – a ‘little’ 12C508 from Microchip, which is more than adequate for such an application. It is mains powered and uses rudimentary voltage regulation by a zener diode.


A relay is used to control the light(s); though this is less elegant than a triac solution, it does avoid any interference from the mains reaching the microcontroller, for example, during thunderstorms. We mustn’t forget this project needs to work very reliably during our absence, whatever happens. The ambient light level is measured by a conventional LDR (light dependent resistor), and the lighting switching threshold is adjustable via P1 to suit the characteristics and positioning of the LDR.

Note that input GP4 of the PIC12C508 is not analogue, but its logic switching threshold is very suitable for this kind of use. The LED connected to GP1 indicates the circuit’s operating mode, selected by grounding or not of GP2 or GP3 via override switch S1. So there are three possible states: permanently off, permanently on, and automatic mode, which is the one normally used. Given the software programmed into the 12C508 (‘firmware’) and the need to generate very long delays so as to arrive at lighting times or an hour or more, it has been necessary to make the MCU operate at a vastly reduced clock frequency.

PCB Layout:
pcb-layout-of-intelligent-presence-sim
PCB Layout Of Intelligent Presence Simulator

In that case, a crystal-controlled clock is no longer suitable, so the R-C network R5/C3 is used instead. For sure, such a clock source is less stable than a crystal, but then in an application like this, that may well be what we’re after as a degree of randomness is a design target instead of a disadvantage. Our suggested PCB shown here takes all the components for this project except of course for S1, S2, and the LDR, which will need to be positioned on the front panel of the case in order to sense the ambient light intensity.

The PCB has been designed for a Finder relay capable of switching 10 A, which ought to prove adequate for lighting your home, unless you live in a replica of the Palace of Versailles. The program to be loaded into the 12C508 is available for free download from the Elektor website as file number 080231-11.zip or from the author’s own website: www.tavernier-c.com. On completion of the solder work the circuit should work immediately and can be checked by switching to manual mode.

The relay should be released in the ‘off’ position and energized in the ‘on’ position. Then all that remains is to adjust the day/night threshold by adjusting potentiometer P1. To do this, you can either use a lot of patience, or else use a voltmeter – digital or analogue, but the latter will need to be electronic so as to be high impedance – connected between GP4 and ground. When the light level below which you want the lighting to be allowed to come on is reached, adjust P1 to read approximately 1.4 V on the voltmeter.

If this value cannot be achieved, owing to the characteristics of your LDR, reduce or increase R8 if necessary to achieve it (LDRs are known to have rather wide production tolerances). Equipped with this inexpensive accessory, your home of course hasn’t become an impregnable fortress, but at least it ought to appear less attractive to burglars than houses that are plunged into darkness for long periods of time, especially in the middle of summer. (www.tavernier-c.com)

COMPONENTS LIST Resistors
R1 = 1k 500mW
R2 = 4k7
R3 = 560R
R4,R6 = 10k
R5 = 7k5
R 7 = LDR
R8 = 470k to 1 M
P1 = 470k potentiometer
Capacitors
C1 = 470µF 25V
C2 = 10µF 25V
C3 = 1nF5
C4 = 10nF
Semiconductors
D1,D2 = 1N4004
D3 = diode zener 4V7 400 mW
LED1 = LED, red
D4 = 1N4148
T1 = BC547
IC1 = PIC12C508, programmed, see Downloads
Miscellaneous
RE1 = relay, 10A contact
S1 = 1-pole 3-way rotary switch
F1 = fuse 100 mA
TR1 = Mains transformer 2x9 V, 1.2 -3 VA
4 PCB terminal blocks, 5 mm lead pitch
5 solder pins