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Discussion Starter #1
ok i wanna make one as i want to hide it in the dash!!
question is how would i make it so i can switch the leds at certain rpm!???example: first green at 4000 then first yellow 5000 then first red 6000??????
i can get l.e.d's from maplins (looked this morning) just need to know what i need to read the voltage from the coil and transfer to light!?

if it helps there was a pack so u can make a sound level meter:)
 

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Yup - you need a frequency to voltage convertor and some electronics to display the voltage over a certain range.

I'm using a PIC chip in my design. It times the interval between the pulses from the coil and calculates the RPM from that.

500 rpm from a standard coil equals 13.3 pulses per second.

You also need to be careful with the electronics side. The back emf from the coil will bung 400 volts through your circuit if you dont filter it properly.

It nowhere near as easy as it looks by the way but I hope to have some sort of design finished and in production by the end of next month.
 

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Should be around £25 all in. I'll post more details when I've got a couple of prototypes knocked up.

Dom
 
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