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Gear indicator project

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Brian Dutton

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I fitted a gear indicator to my bike engined car, it uses a wheel speed sensor and a feed from the tacho to compute the gear. Unfortunately it stops working above 4500rpm. Since the engine revs to 11000, this is a problem. I suspect the unit can't handle the pulse rate from the tacho output.
So can anyone help with a simple divide-by-n circuit using a TI CD4018B chip, to reduce the frequency.
 
4500 rpm is only 75 Hz. That is not a very high upper frequency limit for electronics. Can you post a drawing of your circuit so we can better help? John
 
The gear indicator is an off the shelf design by Biketronix, they have been less than helpfull. I agree that 75Hz is slow, but I don't know how many pulses/rev are generated by the ECU.
I have asked other bikers forums about these displays non so far are positive. My plan was to experiment with a reduced frequency, to see if this had an effect. I have tried reducing the input voltage from a maximum of 10.5 volts, to 6 volts but this had zero effect on the point the display starts to display incorrect values ( a "n" for neutral).
I did try reducing and increasing the wheel speed pulses without effect.
 
I am thinking either the input signal is not good enough or the shift light unit is bad.

Can you hook a scope to the tach signal to see what it looks like below and above 4500 rpm. Does it look different with and without the gear indicator unit in place.
 
I wonder how it should work. Not shifting gears results probably in highest possible engine rpm, but no gear indication. :confused:

Boncuk
 
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