Telegraph Relay Controller

A bit of old-school hacking today. 🙂

I picked up an old J.H. Bunnell telegraph relay, which from what I’ve been able to deduce is a mainline type 2-3 relay made sometime in the late 1800’s. It was missing a few parts, but a binding post from the junk box and a spring from an old floppy drive soon fixed that. I hooked it up to the power supply and hey, whaddya know, it still works!

J.H. Bunnell Relay

Manually turning the relay on and off is fun, but I figured I could do better. So, I programmed an AVR micro controller to tap out some morse code on the relay. The relay draws a little over half an amp at 12 volts, so there’s no way the AVR was going to drive it directly; instead the AVR controls a simple transistor switch that trips the relay. The result? Pure awesomeness:

Now to maybe find some practical use for it. I’m thinking some sort of early-warning system is in order.