#81 Building a 12v relay on a cheap PCB board
While working on one of my projects I needed a 12v relay unfortunately I did not have one on hand and was not about to pay for 1 relay plus shipping.
Luckily I had all the components at hand:
1 green and 1 red led
2x 470 ohm resistors
1x 1k resistor
1x 1N4007 diode
1x bc547 transistor
1x 12v relay
Some solid alarm wire
Very cheap rectangular PCB
For a 5 volt version just replace with a 5v relay and 2x 100 ohm resistors for the LEDs.
Unfortunately the PCB I had was very cheap and I could not fit the screw terminals I had so I had to squeeze them in.
I also used thin alarm wire as i did not need to switch high amps but luckily everything worked out in the end.
It was a bit messy but next time I will use a better quality PCB that doesn’t burn tracks when making solder bridge tracks.
The BC547 also allows switching with 3.3 volt logic but remember to supply the 12v