
Tuesday, 18 November 2014
Toggle switch with Infra Red IR

1000W ICs audio amplifier with PA03
Monday, 17 November 2014
100W Audio Amplifier with TDA7294
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.
Thursday, 13 November 2014
150W LM12 based audio amplifier circuit with explanation
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…
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Wednesday, 12 November 2014
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
Wednesday, 5 November 2014
Automatic Night Lamp with Morning Alarm
A battery backup is provided to power the circuit when mains fails. When mains supply is available, the 9V rechargeable battery charges via diode D5 and resistor R1 with a reasonably constant current. In the event of mains failure, the battery automatically takes up the load without any delay. Diode D5 prevents the battery from discharging backwards following the mains failure and diode D6 provides current path from the battery.
Automatic Night Lamp with Morning Alarm Circuit Diagram:
In total darkness, the specified LDR has a resistance in excess of 280 kilo-ohms. When the resistance of LDR1 increases, a short pulse is applied to trigger pin 2 of IC2 via resistor R2 (150 kilo-ohms). This activates the monostable and its output goes high, causing the white LED to glow. Low-value capacitor C2 maintains the monostable for continuous operation, eliminating the timer effect. By increasing the value of C2, the ‘on’ time of the white LED can be adjusted to a predetermined time. LDR2 and associated components generate the morning alarm at dawn. LDR2 detects the ambient light in the room at sunrise and its resistance gradually falls and transistor T1 starts conducting. When T1 conducts, melody-generator IC UM66 (IC3) gets supply voltage from the emitter of T1 and it starts producing the melody. The musical tone generated by IC3 is standard 0-9V transformer. Diodes D1 through D4 rectify the AC voltage and the resulting DC voltage is smoothed by C1. Regulator IC 7806 gives regulated 6V DC to the circuit.
In total darkness, the specified LDR has a resistance in excess of 280 kilo-ohms. When the resistance of LDR1 increases, a short pulse is applied to trigger pin 2 of IC2 via resistor R2 (150 kilo-ohms). This activates the monostable and its output goes high, causing the white LED to glow. Low-value capacitor C2 maintains the monostable for continuous operation, eliminating the timer effect. By increasing the value of C2, the ‘on’ time of the white LED can be adjusted to a predetermined time. LDR2 and associated components generate the morning alarm at dawn. LDR2 detects the ambient light in the room at sunrise and its resistance gradually falls and transistor T1 starts conducting. When T1 conducts, melody-generator IC UM66 (IC3) gets supply voltage from the emitter of T1 and it starts producing the melody. The musical tone generated by IC3 is amplified by single-transistor amplifier T2. Resistor R7 limits the current to IC3 is amplified by single-transistor amplifier T2. Resistor R7 limits the current to IC3 and zener diode ZD limits the voltage to a safer level of 3.3 volts.
The circuit can be easily assembled on a general-purpose PCB. Enclose it in a good-quality plastic case with provisions for LDR and LED. Use a reflective holder for white LED to get a spotlight effect for reading. Place LDRs away from the white LED, preferably on the backside of the case, to avoid unnecessary illumination. The speaker should be small so as to make the gadget compact.
Sunday, 2 November 2014
LED FLASHER WITH ONE TRANSISTOR
This is a novel flasher circuit using a single driver transistor that takes its flash-rate from a flashing LED. The flasher in the photo is 3mm. An ordinary LED will not work.
The flash rate cannot be altered by the brightness of the high-bright white LED can be adjusted by altering the 1k resistor across the 100u electrolytic to 4k7 or 10k.
The 1k resistor discharges the 100u so that when the transistor turns on, the charging current into the 100u illuminates the white LED.
If a 10k discharge resistor is used, the 100u is not fully discharged and the LED does not flash as bright.
All the parts in the photo are in the same places as in the circuit diagram to make it easy to see how the parts are connected.
Tuesday, 28 October 2014
Alarm Sound with Control Switch
| Alarm Sound with Control Switch |
Monday, 27 October 2014
IC Amplifier with HA13118 Diagram
| IC Amplifier with HA13118 Circuit Diagram |
Saturday, 18 October 2014
High HiFi Power Amplifier with MOSFET
High Power Series HiFi Power Amplifier With MOSFET can modify to increase power output by doubling the final power amplifier is based on the diiginkan. Power generated from doubling the final power amplifier will also double its power output of power amplifier circuit "High Power HiFi Power Amplifier With MOSFET" it.







