Vehicle Speed Sensor - Pulse rate correction - digital correction

Thread Starter

teliocide

Joined Sep 26, 2013
56
I need to match the vss output (non original gearbox) to the pulse rate expected by the cars engine management computer.
There are commercial units:
http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=126/category_id=-1/mode=prod/prd126.htm
I would like to have ago at making my own.
I have done this very crudely in the past with a few cheap chinese ebay bits ie
Frequency to Voltage converter >>>>>Variable resistor>>>>>> Voltage to frequency converter.

Does any one have circuit to do this digitally.??

Thanks
Greg
 

crutschow

Joined Mar 14, 2008
24,111
Can you program a microprocessor?
That's likely the easiest way to go.

Otherwise it would simplify things if you have a specific range of frequency ratio change you want to do, and is it up or down in frequency?
 

Thread Starter

teliocide

Joined Sep 26, 2013
56
Fortran and MS Basic from the mid 1970's when I worked at Kodak Research Labs.
There is more to it than coding.
Some form of mathematical expression is required to describe what is going on.

I have not been able to measure the VSS ouput.
But it is less than required.

I am interested how Dakota Digital achieved this
 
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crutschow

Joined Mar 14, 2008
24,111
Fortran and MS Basic from the mid 1970's
Microprocessors are, of course, available with Basic interpreters or compilers.
I am interested hoe Dakota Digital achieved this
My guess is they used a microprocessor.
One way would be to measure the input pulse period (perhaps with some averaging) and generate output pulses with a shorter or longer period, depending on whether the output frequency should be greater or less than the input frequency.

I suppose that involves a mathematical expression, but it's not that complicated.
You multiply the measured input period by the ratio of the desired input to output frequency ratio to get the output period.
 
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