Sunday 4 January 2009

Reverse is sorted out with a little diode logic :). Speed sensor still not working.

I sorted out reverse with a little diode logic to make my forward / reverse switch work how I want it. The switch is a rotary switch with 3 positions. Forward / Neutral / Reverse.

Start is initiated by turning the key. This provides an interlock so the motor wont start if the switch is knocked accidentally.

I still have some problems with the speed sensor. It is dropping pulses at high RPM. It is a 3kHz unit but something is wrong with it. The max Hz of the sensor should be 4000RPM x 40 teeth on pickup = 2666Hz

See following oscilloscope photos.

Output at 30Hz. Nice and square with a bit of wobble.

Sensor output at 100Hz. Lots of dropped pulses.


Anonymous said...

Hi Mal,
Great to see your getting ever closer to having it on the road!

Bummer about the gear-tooth sensor. From your waveforms, it looks like it is missing both the tooth peaks and valleys at 100 Hz. Could there be too much sensor hysteresis for your particular tooth dimensions where deeper cuts in the teeth may help? Or could your gear have strong magnetic lobes that interfere at certain degree points?

Just guesses on my part, I'm sure you'll get it nailed down! Keep up the good work as we sure enjoy reading your blog!

Take care,
Oregon US

Anonymous said...

Hi Mal,

One other thought... You may find that a Hall type gear-tooth-sensor may work a bit better in this application. A CYGTS99 or similar may work for you. Might even be able to find one similar in an automotive junk yard or your favorite auto parts store...

Take care, Bill