Thursday, 11 September 2014

9V to 5V Voltage Regulator – PCB

In my previous article (9V to 5V Voltage Regulator Plan) I was working on making a small, discrete 5V power regulator with a 9V input voltage. Today, as I had some etchant going to waste, I decided to make this handy little circuit.

I started with toner transfer and then etched the board. After cleaning off the toner and drilling the through-holes, I printed out the silk and glued it to the top of the PCB and set to populating it.

The circuit uses:

  • 1 x LM705;
  • 2 x 100nF electrolytic capacitors;
  • 4 x pin headers
  • 1 x 18mm x 20mm FR4 single sided copper clad board

The soldering was very easy on this board, while it is a little cramped, I started with the pin headers, then the capacitors and finally the regulator.


The input is at the back of the circuit and the output is at the front. I’ve labelled the +/- of the input/output as well as the expected voltage.

The datasheet for the LM7805 says that the input voltage range is 5V to 18V, but the goal for this little circuit is to be embedded in other devices that will have a 9V battery … so I’ve labelled it 9V. If you wanted to use this circuit with other voltages, please be sure that you read and follow the data sheet for the LM7805 (from

As I don’t have my multimeter with me, the only real test that I can perform is a voltage output presence test … that is, if I plug in a battery at input and a load at output, does the load circuit work.

As is fairly usual with my testing, I use my 2 x 2 SMD LED circuit as the load. I plugged in the battery and the load circuit and … light!


I will do some actual voltage tests on the circuit next week when I am in the same state as my multimeter. For now, that’s job done.

This circuit will normally be wired up to feed power to a solderless breadboard when I need a regulated 5V supply, such as when I am testing my ATTiny84/ATTiny85 circuits. I’ll probably make a 3.3V version at some stage, but for now I don’t need one.

Here it is connected to the previously programmed ATTiny85 again, feeding the 2 x 2 SMD LED circuit.


I’ve videoed the LED. This is using a modified version of the pulse function found in the ArduinoISP sketch. The pulse function drives the Heartbeat LED in the source sketch.

9V Battery 5V Regulator – ATTiny85 Power Supply

Oh, and by the way, here is the pulse sketch from the ArduinoISP sketch. The values following the comment (//) are the original values from the Arduino sketch, for reference.

int LED_HB = 0;

//void pulse(int pin, int times);

void setup() {
  pinMode(LED_HB, OUTPUT);
  pulse(LED_HB, 2);

uint8_t hbval = 175; //128;
int8_t hbdelta = 16; //16;

void heartbeat() {
  if (hbval > 225) hbdelta = -hbdelta; //192;
  if (hbval < 16) hbdelta = -hbdelta; //16;
  hbval += hbdelta;
  analogWrite(LED_HB, hbval);
  delay(50); //30;

void loop(void){

#define PTIME 50
void pulse(int pin, int times) {
  do {
    digitalWrite(pin, HIGH);
    digitalWrite(pin, LOW);
  while (times--);

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