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).

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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). 

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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.

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Interfacing Keypad and LCD Embedded Microprocessor

This is circuit for interfacing I/O keypad and LCD that can study in laboratory for student to experience interfacing basic I/O devices to the HCS12 microcontroller mounted on the CML12S-DP256 development board. The keypad that using in this circuit is a standard 4 X 4 matrix keypad with 4 rows and 4 columns. This is the figure of the interfacing of keypad.

The DCM-20434 LCD display is interfaced to the MCU’s SPI-0 serial port through a serial to parallel converter as shown in Figure 3. Figure 3 shows the interface connections between the SPI-0 serial port, the 74HC595 (serial to parallel converter) device, and the LCD-PORT. The DCM-20434 LCD should be configured in four bit mode as the schematic shows DB3 through DB0 connected to ground. This is the interface figure.

To interface the LCD display to the HCS12 MCU you must understand how the physical layer interface circuit is constructed (shown in Schematics for Development Board), how to configure and use the SPI serial port (SPI Serial Bus Document), and how to configure and use the LCD display (DMC-20434 LCD Specifications ).

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I2C Bus Electrical Isolation Diagram Circuit

When the SDA (Serial DAta) lines on both the left and right lines are 1, the circuit is quiescent and optoisolators IC1 and IC2 are not actuated. When the SDA line at the left becomes 0, current flows through the LED in IC1 via R2. The SDA line at the right is then pulled low via D2 and IC1. Optoisolator IC2 does not transfer this 0 to the left, because the polarity of the LED in IC2 is the wrong way around for this level. This arrangement prevents the circuit holding itself in the 0 state for ever. As is seen, the circuit is symmetrical. So, when the SDA line at the right is 0, this is transferred to the left. The lower part of the diagram, intended for the SCL (Serial CLock) line, is identical to the upper part.

Electrical Isolation For I2C Bus Circuit Diagram

Resistors R1, R4, R5, and R8, are the usual 3.3 kΩ pull-up resistors that are obligatory in each I2C line. If these resistors are already present elsewhere in the system, they may be omitted here. The current drawn by the circuit is slightly larger than usual since the pull-up resistors are shunted by the LEDs in the optoisolators and their series resistors. Nevertheless, it remains within the norms laid down in the I2C specification

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Technology Spending Limits and the Auto Sound System

We live in a world that is constantly changing and evolving. We see it every time we buy a new car, a new television, or a new computer. We see it every other month when the iPod is putting out a new an improved model that offers more features, more disk space, and more everything, in a smaller package (well not since they added video but until then, the gadgets were getting smaller while the features were growing exponentially). The truth of the matter is that technology seems to be advancing at a rate that is nearly impossible to keep up with. That being said, you can quite literally drive yourself insane by trying to keep up with the pace of modern technology.

What you need to do in order to maintain proper sanity is decide on a level of technology that you are comfortable and confident with and go with it until it is time (by either necessity or desire) to upgrade. You do not have to be the first to purchase the latest and greatest in software and gadgetry (this has become my mantra: I do not have to be the first to own the great big bad new toy, I will survive gadget deprivation-it isnt working yet but Im ever the optimist). The point is that you do not need to be the first to try every new thing and you will not only wear yourself out by trying but also you bank account, credit cards, and second mortgage. Technology is expensive, especially the newest and latest. If there was any doubt stroll on over to Ebay and see how much Play Station 3s are selling for at the moment-madness and lunacy do not even begin to subscribe the amount of money people are offering to pay for these devices.

Technology is a wonderful thing. It makes life easier for some and a lot more entertaining for others. The same holds true with auto sound systems. The technology exists to make them much more beneficial to car and driver than they have been in the past while offering many more features than ever before. Today you arent even limited to AM and FM. You now have the option of CDs, audio books, MP3s, XML, and digital FM radio, which offers a few bonus features over traditional radio. It really doesnt matter if you have the absolute latest. Most of us can enjoy a great deal of the wonderful technology that is available if we are willing to wait long enough for the prices to go down. I recall, and it wasnt all that long ago, when DVD players sold for no less than $100. You can get them now (about 5 years later) on a regular basis for less than $30. This is only one example of many. PS2s were around $400 when they first hit the market and now can be bought at the whopping price of $120. All around us technology evolves and grows and then prices fall.

The point is spend your money where you want to spend it rather than where you think it should be spent. If you want an auto sound system then get the best one that you feel meets your budget requirements. You do not have to have the top system in the technology food chain in order to have a great sound system that will provide you with years worth of enjoyment. You are the only one that is responsible for the decisions you make. It is up to you to decide where you want the bulk of your money invested when it comes to technological gadgets and goodies. Believe me, Im a gadget geek. I love playing with new toys and gizmos and seeing how they work-really, for me its a thrill. At the same time I realize I cant always be the first to get the new toys I so desperately want to try out so I limit myself and decide which ones are the most important. You must do this for yourself when it comes to auto sound systems.

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Simple 2304 and 3456 MHz Power Amplifiers Circuit Diagram

This is a Simple 2304 and 3456 MHz Power Amplifiers Circuit Diagram

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Latest Mini fm radio Transmitter circuit

Mini fm radio Transmitter circuit

Mini fm radio Transmitter circuit using BF199

This small FM transmitter with a range of about 50 meters designed for hoby. With lots of mini-transmitters then you have a comprehensive, action-packed radio program. Due to the power supply via the USB port of a high frequency stability is achieved. Alternatively, the receiver, a battery 5 to 12 volts to operate.

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IC555 Pulse Timer Control Relay Circuit and explanation

Today we would like to offers solutions for a set time for take control relay and take NO. / NC. contact to apply to control other devices . such as disable or enable the device.
function of this circuit is using IC555 to determine the pulse and a resistor R1 to the period of time.
R1           #Seconds
100k         2
220k         3
470k         6
1M           15
The increase provides more time to increase the value of the Capacitor.

Electronic Part List
R1 = 1 Meg, Preset Pot
R2 = 10K  
R3,R4 = 1K
C1 = 10uF, 16V
C2 = 0.01uF
T1 = BC547 (Gen Purp NPN)
T2 = 2N2222 (Hi Current NPN)
D1 = 1N4001 (Gen Purp Si)
IC1 = 555 (Lo-Power version)
RLA1 = Relay, 9V (amps of your choice)

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88 108 MHz Voltage Controlled Oscilator for PLL Controller This Circuit will explain the PLL unit and the VCO Voltage Controlled Oscillator which w

88-108 MHz Voltage Controlled Oscilator for PLL Controller

This Circuit will explain the PLL unit and the VCO (Voltage Controlled Oscillator) which will create the FM modulated RF signal up to 400mW. the schematic to follow my function description. The main oscillator is based around the transistor Q1. This oscillator is called Colpitts oscillator and it is voltage controlled to achieve FM frequency modulation) and PLL control.

Q1 should be a HF transistor to work well, but in this case I have used a cheap and common BC817 transistor which works great. The oscillator needs a LC tank to oscillate properly. In this case the LC tank consist of L1 with the varicap D1 and the two capacitor (C4, C5) at the base-emitter of the transistor. The value of C1 will set the VCO range.

The large value of C1 the wider will the VCO range be. Since the capacitance of the varicap (D1) is dependent of the voltage over it, the capacitance will change with changed voltage. When the voltage change, so will the oscillating frequency. In this way you achieve a VCO function. You can use many different varicap diod to get it working. In my case I use a varicap (SMV1251) which has a wide range 3-55pF to secure the VCO range (88 to 108MHz).

Inside the dashed blue box you will find the audio modulation unit. This unit also include a second varicap (D2). This varicap is biased with a DC voltage about 3-4 volt DC. This varcap is also included in the LC tank by a capacitor (C2) of 3.3pF. The input audio will passes the capacitor (C15) and be added to the DC voltage. Since the input audio voltage change in amplitude, the total voltage over the varicap (D2) will also change. As an effect of this the capacitance will change and so will the LC tank frequency.

You have a Frequency Modulation of the carrier signal. The modulation depth is set by the input amplitude. The signal should be around 1Vpp. Just connect the audio to negative side of C15. Now you wonder why I dont use the first varicap (D1) to modulate the signal? I could do that if the frequency would be fixed, but in this project the frequency range is 88 to 108MHz.

If you look at the varicap curve to the left of the schematic. You can easily see that the relative capacitance change more at lower voltage than it does at higher voltage. Imagine I use an audio signal with constant amplitude. If I would modulated the (D1) varicap with this amplitude the modulation depth would differ depending on the voltage over the varicap (D1). Remember that the voltage over varicap (D1) is about 0V at 88MHz and +5V at 108MHz. By use two varicap (D1) and (D2) I get the same modulation depth from 88 to 108MHz.

Now, look at the right of the LMX2322 circuit and you find the reference frequency oscillator VCTCXO. This oscillator is based on a very accurate VCTCXO (Voltage Controlled Temperature controlled Crystal Oscillator) at 16.8MHz. Pin 1 is the calibration input. The voltage here should be 2.5 Volt. The performance of the VCTCXO crystal in this construction is so good that you do not need to make any reference tuning.

A small portion of the VCO energy is feed back to the PLL circuit through resistor (R4) and (C16). The PLL will then use the VCO frequency to regulate the tuning voltage. At pin 5 of LMX2322 you will find a PLL filter to form the (Vtune) which is the regulating voltage of the VCO. The PLL try to regulate the (Vtune) so the VCO oscillator frequency is locked to desired frequency. You will also find the TP (test Point) here.

The last part we havent discussed is the RF power amplifier (Q2). Some energy from the VCO is taped by (C6) to the base of the (Q2). Q2 should be a RF transistor to obtain best RF amplification. To use a BC817 here will work, but not good.

The emitter resistor (R12 and R16) set the current through this transistor and with R12, R16 = 100 ohm and +9V power supply you will easy have 150mW of output power into 50 ohm load. You can lower the resistors (R12, R16) to get high power, but please dont overload this poor transistor, it will be hot and burn up… Current consumption of VCO unit = 60 mA @ 9V.

Printed Circuit Board (PCB.pdf)
This is how the real board should look when you are going to solder the components.
It is a board made for surface mounted components, so the cuppar is on the top layer.

Parts List
100 = R7, R12, R16
330 = R4
1k = R1, R2, R3, R10
3.3k = R11
10k = R5, R6, R14, R17
20k = R13
43k = R9
100k = R8, R15
3.3pF = C2, C16
15pF = C4, C6
22pF = C5
1nF = C1, C3, C8, C17, C22, C23
100nF = C7, C9, C11, C12, C13, C14, C19, C20
2.2uF = C15, C18
220uF = C10, C21
L1 = 3 turns diam 6.5mm (Everything from 6 to 7 mm will work good!)
L2, L3, L4 = 10uH
D1, D2 = SMV1251
Q1 = BC817-25
Q2 = BFG193
X1 = 16.800 MHz VCTCXO Reference oscillator
V1 = 78L05
IC1 = LMX2322 

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HA 13118 bassed 18W audio amplifier circuit and explanation

This audio amplifier circuit diagram is a class AB audio power amplifier based on the Hitachi HA13118 audio integrated circuit . The Hitachi HA13118 audio amplifier circuit provide a high power output from a low voltage supply using the bridge tied load method, and a high gain of 55dB. This audio amplifier is ideal for audio applications where the input signal has a very low level .

The Hitachi HA13118 audio amplifier circuit can provide a maximum 18W power in a 4 ohms load using 18 volts DC power Supply but also can be obtained various output power : > 5W RMS on 8 ohm load using 18V DC supply , > 6W RMS on 4 ohm load using 12V DC supply .

Other specifications for this amplifier are :

S/N ratio : > 70 dB , THD <0.2% @ 1w , freq. response : ~ 30 hz to 30 khz, input level : <25 mv , input impedance ~ 30 k ohm .

For the Hitachi HA13118 audio amplifier circuit you will need a power supply that will provide a DC voltage between 8 and 18Vand at least 1 to 2 Amps.

If you want to obtain the maximum output power you will need a power supply that will provide 18 volts DC at more than 2 A , and if you will use a 4 ohms speaker .

The construction of this power supply is very simple and is require few external components .

Be careful when soldering the IC not to use excessive heat. If it’s possible use some heat sink compound between the heat sink & the IC .

If you need volume control or to attenuate the input signal you can connect a logarithmic potentiometer at the input pin .

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Latest Automatic Railway Gate Control Track Switching circuit

Present project is designed using 8051 microcontroller to avoid railway accidents happening at unattended railway gates, if implemented in spirit. This project utilizes two powerful IR transmitters and two receivers; one pair of transmitter and receiver is fixed at up side (from where the train comes) at a level higher than a human being in exact alignment and similarly the other pair is fixed at down side of the train direction. Sensor activation time is so adjusted by calculating the time taken at a certain speed to cross at least one compartment of standard minimum size of the Indian railway. We have considered 5 seconds for this project. Sensors are fixed at 1km on both sides of the gate. We call the sensor along the train direction as ‘foreside sensor’ and the other as ‘aft side sensor’. When foreside receiver gets activated, the gate motor is turned on in one direction and the gate is closed and stays closed until the train crosses the gate and reaches aft side sensors. When aft side receiver gets activated motor turns in opposite direction and gate opens and motor stops. Buzzer will immediately sound at the fore side receiver activation and gate will close after 5 seconds, so giving time to drivers to clear gate area in order to avoid trapping between the gates and stop sound after the train has crossed.

The same principle is applied for track switching. Considering a situation wherein an express train and a local train are traveling in opposite directions on the same track; the express train is allowed to travel on the same track and the local train has to switch on to the other track. Two sensors are placed at the either sides of the junction where the track switches. If there’s a train approaching from the other side, then another sensor placed along that direction gets activated and will send an interrupt to the controller. The interrupt service routine switches the track. Indicator lights have been provided to avoid collisions. Here the switching operation is performed using a stepper motor. Assuming that within a certain delay, the train has passed the track is switched back to its original position, allowing the first train to pass without any interruption. This concept of track switching can be applied at 1km distance from the stations.The project is simple to implement and subject to further improvement.

Model of Automatic Railway Gate Control & Track Switching

Gate Control:

Railways being the cheapest mode of transportation are preferred over all the other means .When we go through the daily newspapers we come across many railway accidents occurring at unmanned railway crossings. This is mainly due to the carelessness in manual operations or lack of workers. We, in this project has come up with a solution for the same. Using simple electronic components we have tried to automate the control of railway gates. As a train approaches the railway crossing from either side, the sensors placed at a certain distance from the gate detects the approaching train and accordingly controls the operation of the gate. Also an indicator light has been provided to alert the motorists about the approaching train.

Gate control

Hardware Description

The project consists of four main parts:
8051 microcontroller
IR Transmitter
IR Receiver
Stepper Motor Circuit

8051 Microcontroller

The I/O ports of the 8051 are expanded by connecting it to an 8255 chip. The 8255 is programmed as a simple I/O port for connection with devices such as LEDs, stepper motors and sensors. More details of the 8255 are given later.
The following block diagram shows the various devices connected to the different ports of an 8255. The ports are each 8-bit and are named A, B and C. The individual ports of the 8255 can be programmed to be input or output, and can be changed dynamically. The control register is programmed in simple I/O mode with port A, port B and port C (upper) as output ports and port C (lower) as an input port.

Block diagram of 8051 Microcontroller

IR Circuits

This circuit has two stages: a transmitter unit and a receiver unit. The transmitter unit consists of an infrared LED and its associated circuitry.

IR Transitter

The transmitter circuit consists of the following components:
IC 555
Resistors
Capacitors
IR LED

The IR LED emitting infrared light is put on in the transmitting unit. To generate IR signal, 555 IC based astable multivibrator is used. Infrared LED is driven through transistor BC 548.

IC 555 is used to construct an astable multivibrator which has two quasi-stable states. It generates a square wave of frequency 38kHz and amplitude 5Volts. It is required to switch ‘ON’ the IR LED.

IR Transmitter

IR Receiver

The receiver circuit consists of the following components:
TSOP1738 (sensor)
IC 555
Resistors
Capacitors

The receiver unit consists of a sensor and its associated circuitry. In receiver section, the first part is a sensor, which detects IR pulses transmitted by IR-LED. Whenever a train crosses the sensor, the output of IR sensor momentarily transits through a low state. As a result the monostable is triggered and a short pulse is applied to the port pin of the 8051 microcontroller. On receiving a pulse from the sensor circuit, the controller activates the circuitry required for closing and opening of the gates and for track switching. The IR receiver circuit is shown in the figure below.

IR Receiver

Stepper motor circuit

Stepper motor circuit

Here a stepper motor is used for controlling the gates. A stepper motor is a widely used device that translates electrical pulses into mechanical movement. They function as their name suggests – they “step” a little bit at a time. Steppers don’t simply respond to a clock signal. They have several windings which need to be energized in the correct sequence before the motor’s shaft will rotate. Reversing the order of the sequence will cause the motor to rotate the other way.

Track Switching

Using the same principle as that for gate control, we have developed a concept of automatic track switching. Considering a situation wherein an express train and a local train are travelling in opposite directions on the same track; the express train is allowed to travel on the same track and the local train has to switch on to the other track. Indicator lights have been provided to avoid collisions .Here the switching operation is performed using a stepper motor. In practical purposes this can be achieved using electromagnets.

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