Motorcycle Speedo Healer

My brothers VTR1000F has had it's motor rebuilt after it chewed through it's valves one day. His bike has never had a very accurate speedo and it always seemed be be reading fast. So after he got his engine fixed and back together I had a look at all the cabling and the speedo itself. The speedo signal is simply a TTL pulse with a varying frequency. At first we though the sensor was busted, so we replaced it with another. But in the end it would appear that the original owner of the bike had changed the front and rear sprockets up and down a tooth each giving an error at the meter of over 20%!.

So, I built the above little tiny board to correct this error and make his speedo much more accurate. It's basically a frequency shifter that can move the frequency of the incoming signal up or down a fixed percentage. This is controlled by the jumpers.

This was my first double-sided doughnut board, and also the first time I've used Kapton tape to mount SOIC. It worked rather well and I was very happy with the results. It was a little fiddly but well worth the effort. I could have built a custom board, but I had this built in less than 12 hours from start to finish. If I had etched the board I would have been still doing the layout!