I have a speedometer for a bike that uses a reed switch and magnet to count rotations per sound and calculate speed. My problem is the wheel on the bike is too small for the speedometer to calculate (to many rotations per second). I’m tiring to build a circuit that will output every other magnetic latch rotation to the speedo. Half the rotations per second. I know how to do this with 2 relays, but I don’t want to waste the battery power to drive them every time I ride. I would prefer to do the process with an IC. Does anyone have any ideas?

 

A low power, low cost pic microcontroller. Write the code to output every other pulse or whatever is needed to get an accurate speed reading. It will be easy to change if you dont get it right the first time. Or use google for some pulse-skipper circuit that can be built with logic gates & prolly a flip flop or two. Also low power.

 

To divide a frequency by 2, all you need is a flip flop such as the 4013.

You will also need gating and possibly bounce suppression. So an extra Schmitt Trigger IC such as the 40106 will be required.

The 40106 has 6 Schmitt Triggers in it, so one can be used for bounce suppression and one for the gate (a resistor and diode gate followed by the Schmitt).

Search these forums for "flip flop", "counter" & "bounce suppressor"

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Len

 

I have constructed my circuit and it works perfectly with an input from my frequency generator. However I can’t seem to get the de-bounce suppressed when using a “real world” relay or momentary push button. I have tried a variety of different R/C combinations on the input with no luck. Any idea on how to help fix the de-bounce suppression issue?

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