Electronics - Speedometer / Odometer

This one was made way back in April 1998... my first electronics project... I still have the cycle and the dynamo, but the speedo is missing:( I do have the first boards we made for it... disassembled of course.

speedo old

Basically I was using pulses from the dynamo to detect speed. the faster u pedal, the more pulses I get per second.

The circuitry was in 2 basic components. a counter/driver/display board and a control/display mode set board.

As anyone knows, to show a reading based on an input pulse train u need a counter equipped with a latch. the latch circuitry came in the form of a hex Schmidt trigger NOT gate. that is for the speedometer side.

The odometer requires a counter. a simple ripple counter will do. if I remember correctly (and i DO;) it was 1440 pulses for each 100m. a simple 2 digit display and it counts upto 10km and 99kph. on a cycle that's too much...

Then a switch to changeover the 2 displays (Speedo/Odo) all of it fit in this incredibly small (thanks to design and build-it-yourself PCBs that took us 2 tries to get right) I'll put the pics later. We got this cool acrylic cabinet made for us and mounted it on the handle bar. Battery pack went under the seat, and of course the dynamo is fixed to the back wheel.

I'm thinkin' of building my own horn with my own 'ring tones' next. I have access to the technology, its the same one we built for one of our custom chime clock for my dad. only problem is i barely use the cycle these days