Daddylonglegs
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| posted on 4/4/11 at 01:09 PM |
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Rev Counter Needed
Further to my recent thread about the rev counter not working, I plugged my function generator into it and set it to give a sinewave output but not
too sure what frequency or level etc. it would be expecting. I managed to get it responding to an increase in frequency output but it didn't
seem to be happy until after around 450 rpm. The needle seemed to be sticking going up and going down at that sort of reading.
So I am now assuming it's foobarred, and am looking for a replacement. It is a VDO 80mm so if anyone has anything suitable for a 2L pinto on
points or knows where I could get one without breaking the bank I would be grateful.
I don't really want to have to hack the dash around too much as all the wiring is in place so it would be a PITA.
Thanks.
John
It looks like the Midget is winning at the moment......
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MikeRJ
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| posted on 4/4/11 at 03:01 PM |
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I have seen exactly the symptoms you have observed by driving a tachometer with the incorrect waveform.
What output level did you set the function generator to? The tacho is going to be expecting at least 12v and the older ones may need to see the back
EMF from the coil which could be ~200-300v. A sinusoidal waveform is also incorrect, it should be more like a pulse waveform with about 0.3 to 0.4
duty cycle if it is designed for use with a points system.
[Edited on 4/4/11 by MikeRJ]
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Daddylonglegs
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| posted on 4/4/11 at 03:30 PM |
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OK thanks Mike. I tried a few settings but now I know the rough area I'm looking for I can try again. The function generator can give sinewave,
square wave and also pulses IIRC. I can't remember what O/P level it goes up to, but when I tried it, the needle was moving niceley betwee
around 450 and the end of scale as I increased the frequency for a given ouput level.
I'll have a play later. If that doesn't work then I'll give it one last go in the car when I get the engine running for more than a
few seconds.
JB
It looks like the Midget is winning at the moment......
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