Electronic switch for LED lights, 4 channels, 9 to 24 volts in, 5 volts out. Uses an AVR ATtiny2313 microcontroller.

Table of contents

Details

I used to have a very small apartment, and in that apartment I made a lot of the LED lights myself. To make it easier to control and power them I also built this electronic light switch. With a voltage regulator, and large heat-sink, it took 9 to 24 volts in; and gave out four channels of 5 volts. I used dual-color red and green LEDs to show the state of each output, and push-buttons to toggle them. After 10 seconds on inactivity the LEDs would turn off. The maximum load pr. channel were 500mA, not a lot but enough to drive some LEDs.

Power to the module was provided with a power jack at the bottom, and the outputs and signals through a 9 pin d-sub plug. I used a multicore cable down to a junction box, and from there to all the different LED lights. This did leave me with a lot of cables going to all the different lights, but I was single and didn’t really care.

The unit had a “lights out” input that turned all the outputs off. This allowed some external controller or service to turn off the lights when I left or went to bed. But the lights could only be turned back on using the push-buttons.

Using relays the electronic switch module could of course be used to control all kinds of stuff. But I built it to control and power the LED lights listed below.

Unit complete, mounted to the wall

Lights

I used this unit to power and control three lights in my apartment:

  • Two channels were used for four dual color LEDs. One channel for the white lights, and one for the colored.
  • A green LED in the pot of my tiny Bonsai tree.
  • And two LED dot lights mounted in the window frame of my living room window.

Video

I/O

Inputs

  1. PA.0 Push button 1
  2. PA.1 Push button 2
  3. PD.0 Push button 3
  4. PD.1 Push button 4
  5. PD.2 Signal to turn all lights off

Outputs

Status LED

  1. PB.0 LED 1 green
  2. PB.1 LED 1 red
  3. PB.2 LED 2 green
  4. PB.3 LED 2 red
  5. PB.4 LED 3 green
  6. PB.5 LED 3 red
  7. PB.6 LED 4 green
  8. PB.7 LED 4 red

LED light outputs

  1. PD.3 LED lighting 1
  2. PD.4 LED lighting 2
  3. PD.5 LED lighting 3
  4. PD.6 LED lighting 4

D-Sub 9-pin

  1. LED lighting 1
  2. LED lighting 2
  3. LED lighting 3
  4. LED lighting 4
  5. Lights out -12V
  6. Lights out +12V
  7. -5V out
  8. +5V out

Source code

Photos

Assembly, wires
Enclosure front
Stripboard with indication LEDs
Inside enclosure during assembly
Controller board mounted
Power wires connected to voltage regulator
AVR ATtiny2313 on controller board
Inside electronic switch
Junction box for LED cables

Schematic drawing

Electronic switch schematics

Parts list

  • 1 × AVR ATtiny2313-20PU, DIL-20, 20 MHz, 18 I/Os
  • 1 × Capacitor, aluminium electrolytic, 10 µF, 25V
  • 2 × Capacitor, aluminium electrolytic, 47 µF, 25V
  • 1 × Capacitor, ceramic, 1 nF, 100V
  • 1 × D-sub soldering cups, 9 pin female
  • 1 × DIL socket, 20-pin, 7.62mm
  • 1 × DIL socket, 6-pin, 7.62mm
  • 1 × Diode, rectifier, 1 A, 400V, 1N4004
  • 1 × Enclosure, plastic (1591 FL), 120x65x40mm, flange
  • 1 × Enclosure, plastic (1591), 112x62x31mm
  • 1 × Fuse 5x20 mm, 500 mA, fast-acting
  • 1 × Fuse holder, open, PCB, 5x20mm
  • 1 × Fuse holder, open, PCB, Protective cover
  • 1 × Heat conducting film for heatsink, Adhesive, TO220
  • 1 × Heatsink, 6K/W @ 10W, 37.5mm 49g
  • 4 × LED 5mm, Red/Green, 2.0 2.1V, 10mA, 100 63mcd, 30°
  • 4 × LED holder 5mm, RTC51, black plastic
  • 1 × Optocoupler, single, CNY17F-3, DIL-6
  • 1 × Power jack, panel, 2.1mm, plastic housing
  • 13 × Resistor, carbon film, 0.25W, 330 Ω, 5%
  • 5 × Resistor, carbon film, 0.25W, 4.7 kΩ, 5%
  • 5 × Resistor, carbon film, 0.25W, 10 kΩ, 5%
  • 1 × Resistor, metal film, 0.6W, 1 kΩ, 1%
  • 13 × Straight pin header, female, Single row, 2.54mm
  • 13 × Straight pin header, male, Single row, 2.54mm
  • 4 × Switch, push-button, 1-pole, 1A, 50VAC, on-(off)
  • 2 × Terminal block, PCB, screw, 5mm 2-pin
  • 4 × Transistor, NPN, 800 mA, 45V, 0.625W, BC337-25
  • 1 × Voltage regulator +5V, 1 A, 7805PI
  • 1 m Wire, stranded, 0.22mm2, Black
  • 3 m Wire, stranded, 0.22mm2, Grey
  • 1 m Wire, stranded, 0.22mm2, Red
  • 3 m Wire, stranded, 0.22mm2, Yellow