I really like TV-B-Gone by Mitch Altman. The idea to have an universal remote to switch off any TV set is just marvellous! But for some real sneaky operation I wanted a much smaller version which perfectly fits into my pocket. So how about a small experiment how small you can go (and still solder by hand). So here it is: (most probably) the world smallest implementation of TV-B-Gone:
The µTVBG is based on the ATTINY85 implementation by Lady Ada. I just downloaded the schematics and replaced some parts, reduced the number of IR diodes and did a new board layout. Nothing special. Even the firmware works unchanged.The whole board measures a mere 1.4 cm to 2.5 cm – small enough to fit in in every pocket.
All parts are SMT 0603 parts, the transistors are the good old BC850C and as IR diodes I used the Osram SFH 4600 (I think I got quite a soft spot for all those Osram LED stuff, more by accident I use it more or less exclusively – they have great parts, are at least designed by German engineers). The SF 4600 deliver 30 mW of power at 940nm wave length, they look good and can be used flat or as side looker (as I have done here). Currently they are being replaced by the SFH 4641. The switch is a C & K Components KR221G, which is good quality and gives quite an good tactile feeling.
As you can see in the above picture I was able to completely mess up the SFH 4600 footprint – twice as wide as it should be. But with a piece of old wire it was no problem to fix it. You can see, you can even air wire stuff in SMT.
The board is powered by a CR1220 lithium battery, placed on the bottom of the board.
Why an SMT TV-B-Gone clone?
First of all I wanted a real small version – and I achieved that. Second I wanted to test if hand soldering of 0603 is feasible – which it is. 0805 is much easier, but consumes far more board space.
But the main reason is that I want to encourage everybody to try some SMT work. You can do a lot of cool stuff with it, cramp a lot of functionality in a very small board space. And you get real cool components for SMT. Most modern chips are developed as SMT-version only and if you stick to through-the-hole stuff you will never be able to use them (OK, you can get your breakout board at SparkFun). If you managed to do some SMT you are able to pick from thousands of alternatives from major vendors. And the hardest thing about SMT is to get over the fear that it is too small, which it is not – in most cases. So go for it!