Tragedy has struck! I lost the remote control for my amplifier. If I want to turn the music up, I have to get out of my chair and walk across the room. This is unacceptable!
So I need a new remote. I could have bought a replacement controller, or one of those universal ones that are pretty cheap these days but being an electronics guy, I decided to build one. From scratch. Using parts from my junk box.
So what I found was this:
A PIC10F206 low-power micro computer (don’t we all have these lying around?)
Some ugly blue fob cases left over from an old project that was never finished
Various surface-mount resistors and capacitors
Some small surface-mount pushbuttons
LEDs of various colours (but not infra-red)
CR2032 coin cell batteries and holders
Well the show stopper is the lack of infra-red LEDs so I guess I’m going to have to buy one of those. Still it should only cost a few cents and other than that I’ve got enough parts to do the job.
The PIC micro is seriously small but it can output 25 milliamps from it’s I/O pins so I should be able to drive the IR LED directly from that. Here is the circuit I designed:
It’s a pretty simple design. The PIC has an internal oscillator so there’s no need for a crystal. P1 is the PICKit in-circuit programming connector. The PIC also has built-in pull-ups which means there is no need for pull-up resistors on the pushbuttons.
I calculated the resistor values to achieve the 25mA maximum current through the IR LED and added a plain red LED so you can see it working.
Now I could build this on some prototyping board or just hand-wire it but it so happens that being a freelance electronics designer, I’m always getting printed circuit boards made for various clients. So I slipped a board design in with a batch of 30 other boards that were going to a Chinese board factory – I got my PCB almost for free.
Assembling the PCB was dead easy, it’s got to be the simplest PCB I have ever designed. Only 10 parts on the whole thing and a single layer board. In fact, I got my 11-year old son to do most of the soldering.
Of course, the PIC is just a computer so it won’t do anything until I program it. In Part 2 I’ll get onto the software…