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Gear indicator project

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Brian Dutton

New Member
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.
 

jpanhalt

Well-Known Member
Most Helpful Member
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
 

Brian Dutton

New Member
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.
 

3v0

Coop Build Coordinator
Forum Supporter
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.
 

Boncuk

New Member
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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