Dual Adjustable Power Supply +/- 1.2V to 30V DC. 1.5Amp


This project is a solution to power up most of devices or projects required dual (+/-) adjustable power supply. The circuit is based on LM317 positive and LM337 negative voltage regulator. LM317  series of adjustable 3 terminal regulator is capable of supplying in excess of 1.5A over a  1.2V to 30V DC output range, due to TO3 package of  IC and large heat sink the power supply can handle maximum load  current.

Output: +/- 1.2 to 30V DC
Output Current: 1.5Amps
Supply Input: 24V-0-24V AC, 2Amps Center tape Transformer
CN1: Transformer Connections
CN3: +/- Dual Supply Outputs
P1: Positive Voltage Adjust
P2: Negative Voltage Adjust
D1: Positive Power Indicator
D2: Negative Power Indicator







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Two Channel Relay Board

twochannel relay board

2 channel Relay driver project can be controlled by feeding 2-12V trigger voltage, Very useful project for application like Micro-Controller based projects, Remote controller, Lamp on Off, and any circuits which required isolated high current and high voltage switching by applying any TTL or CMOS level voltage. Two LED works as operation indicator while in , 3 pins screw terminals to connect load and provides  both normally open and normally closed switching.





  • Input: 12 VDC @ 84 mA
  • Output: Two SPDT relay
  • Relay specification: 5 A @ 230 VAC
  • Trigger level : 2 to 12 VDC
  • Header connector for connecting power and trigger voltage
  • LED on each channel indicates relay status
  • Power Battery Terminal (PBT) for easy relay output connection
  • Four mounting holes of 3.2 mm each
  • PCB dimensions 49 mm x 68 mm


Two Channel Relay Board

Light Sensitive Switch Single Transistor Based

Light Sensitive Switch is a simple project which operates a relay when light falls on the LDR.

Input : 12 V @ 55 mA
Relay output : NC-C-NO
Onboard preset to set the level
Power-On LED indicator
Relay On LED indicator
Power Battery Terminal (PBT) for easy relay output connection
Four mounting holes of 3.2 mm each
PCB dimensions 44 mm x 49 mm



Light Sensitive Switch Schematic

Light Sensitive Switch Schematic


Light Sensitive Switch PCB and Parts List

Light Sensitive Switch PCB and Parts List

LED VU Meter 5LEDs CH1403 or LB1403 IC


5 LED VU Meter project is based on LB1403/CH1403 IC from SANYO, which will indicates the volume level of the audio signal it senses.


 Power supply : 6 to 12 VDC @ 90 mA
Lighting levels remain stable to line regulation because of on-chip voltage reference
LED’s are driven by a constant current
Onboard presets to adjust input sensitivity
Terminal pins for connecting power supply, audio input
Four mounting holes of 3.2 mm each
PCB dimensions 34 mm x 52 mm



Tiny Mic Pre-Amplifier


The Tiny Mic Pre-Amplifier project is based on a single transistor.  It amplifies the output of the electret condenser microphone. The project amplify low level signal coming from microphone and then provide sufficient voltage level to drive power audio amplifier. Good choice for Karaoke.

Power supply : 5 ~ 9 VDC @ 2 mA
PCB dimensions 26 mm x 56 mm




Mini Stereo Audio Amplifier TDA2822


Mini Stereo Audio Amplifier project is designed for portable radio players and other building block projects.  It is based on TDA2822 IC.


 Power supply : Upto 12 VDC
 Output : 1 W, 8 ?  for 12 VDC / 20 mW, 32 ? for 3 VDC
 Input resistance 100 K?
 Low crossover distortion, Low quiescent current
 Berg connector for connecting audio input, power supply and outputs
 Onboard Presets to adjust volume
 Power-On LED indicator
 Four mounting holes of 3.2 mm each
 PCB dimensions 50 mm x 36 mm



6.5W Stereo Audio Amplifier Based on TDA2004


The 6.5W Stereo Audio Amplifier project built around TDA2004 IC. The TDA2004 is a class B dual audio power amplifier, specifically designed for car radio applications etc.


Power supply input 15 VDC
Output power: 2 X 6.5 W, 4 Ohm / 2 X 10 W, 2 Ohm
Short circuit, thermal shut-down, load dump voltage surge protection
Terminal pins for connecting left and right audio signal inputs
Header connector for connecting potentiometer (POT) for volume adjustment
Screw terminal connector for easy supply input and speaker output connection
Power-On LED indicator
Heat-sink for IC
PCB dimensions 67 mm x 73 mm

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Small Signal Amplifier (Pre-Amplifier) For Audio Signal


The Stereo small level audio signal amplifier has been developed to amplify the low level stereo audio signal, without changing other parameters of the waveform such as frequency and shape of the signal. This circuit  has been designed to amplify signals in the range of 20Hz to 20 kHz. Circuit amplify the low level signals from microphones, ultra-sonic transducer and other audio signal source. The project amplify low level signal and then provide sufficient voltage level to drive power audio amplifier. Gain of the amplifier can be change by onboard preset. Circuit has preset on output to set the audio signal level.


  • Power supply: 12 – 24 VDC @ 40 mA
  • Gain 50
  • Onboard PRESET to adjust Gain
  • On Board Preset on Output to set the audio level Level
  • Header connector for connecting of input and output
  • Terminal pins for connecting power supply input
  • Power-On LED indicator
  • PCB dimensions 47 mm x 58 mm
  • Four mounting holes of 3.2 mm eactch





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