Speed sensor signal conversion

Thread Starter

Zaqu

Joined May 23, 2019
1
Hey guys. I changed the gauges on my 250cc maxi scooter with the ones from a later model that basically looks the same except some minor details, but with fancier instruments, tachometer included. The problem is that the newer model uses a 3 wire speed sensor mounted around the wheel spindle, while the sensor on my model is a 2 wire sensor that reads a series of 32 teeth on the wheel. While the new speedometer seems to understand the signal is getting from the old sensor, the needle goes very high, above 140km/h while I barely reach 10-20km/h. Is there a way to convert the signal so that the speedometer shows the actual speed? So far I have tried a simple circuit using a 4017 frequency divider but without results... dividing from 2 up until to 10 did not seem to have any effect on the signal from the sensor, needle still going high as crazy. I'am kinda out of ideas, besides just getting the whole wheel plus the sensor of the newer model.
Photo 1: the wheel and the sensor on my model.
Photo 2 and 3 the wheel and the sensor from the newer model.
 

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Alec_t

Joined Sep 17, 2013
10,355
I agree that a 3-wire sensor is most likely a Hall effect type, so the new gauge might not tolerate a bipolar signal of varying amplitude from your existing 2-wire sensor.
dividing from 2 up until to 10 did not seem to have any effect on the signal from the sensor
I don't understand. Surely the amplitude of the divider output would be fixed and the signal frequency would be lower? Or do you mean there was no change to the gauge behaviour?
 
I'm confused. I counted the teeth in photo one and there were more than 32. 36 maybe? I don't see any teeth in photo 2. I'm guessing the new cluster uses a different type of sensor that doesn't measure the timing of the teeth. If the new speedometer is looking for something like a magnetic signal rather than a timing pulse from a toothed speed sensor wheel I don't see how you will ever get it to work. It would be like looking for an FM station on an AM radio. Have you tried putting the wheel and sensor from the newer scooter on your bike to see if that solves your problem? I don't know anything about scooters so I'm just going by what I can see in the pictures.
 
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