I am look for a way to slow down the frequency from a Hall effect sensor does anyone have a schematic to build a divider possibly I need to slow the frequency down by about 13%
There frequency dividers and you can make a divide-by-2 with a flip-flop, The only circuits I've seen divide by factors of 2.
With digital logic you can build a circuit to divide by any number.
Do you have a schematic on how to make one
Not possible with an integer divider. One approach is to multiply counts by 7 and then divide by 8, for 12.5% reduction. Or just count pulses, and ignore every 8th pulse.
If you explain the project, maybe you will get better suggestions.
Why?
Did I miss the link to that device? .. and which arduino you are using? ... and oh,
Maybe clocking TC1 externally could work for you.
Ok I have a speedometer in my car that produces a square wave signal with the original gear in the rear differential it produced 4000 pulses per mile now after a gear change it has increased 4500 pulses per mile which has the speedometer reading fast than you are actually going I am looking for a way to slow the signal back down to the 4000 pulses per mile so my Speedo is back somewhat accurate?
4000/4500 = 0.89, or about 10% reduction.
One idea would be to write a couple of lines of code that reads and outputs the pulses, skipping every tenth pulse.
4000:4500 is a 8:9 ratio, so skip every 9th pulse.
Leo..
If each pulse is being used to compute a speed by the car's computer, then wouldn't it produce nine values just as it is currently doing, then the next one would be halved as the gap between the 9th and 10th pulse has doubled.
The car's computer might not process the pulse that way so perhaps it's necessary to know how it works at the detailed level. Does it use the time gap between pulses or the duration of each pulse?
The car has a 12 points on a rotor that corresponds to 12 pulses per revolution and it knows that it should pulse 4000 times to go a mile but mine since gear change pulse 4500 times in one mile so it thinks you are traveling faster than you are actually going
Yes, that was clear. Might keep you from getting a speeding citation, if you left it as is.
It use the time gap between pulse to determine speed
Then multiply that time value by 8/9 before using it.
Leo..
Is your speedometer original equipment? Dealers can adjust speedometers for different tire sizes. Maybe for different differential ratios?
Even on a 1970 Oldsmobile? 
Didn't see where OP said which make and year.
User name.
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