Stopping negative voltage

[Steevo25]

Hi All,

I have a small electronics issue you may be able to help me with.

I have an alternator which provides me with an RPM pulse. The pulse goes from 7v to -7v. This feeds a decade counter which in turn feeds my picaxe.

It seems that the -7.5v is confusing the decade counter because it seems to be counting twice for each pulse.

What can I add to the circuit before the decade counter to clamp the input pulse from the alternator to stay between 7v and zero?

Many thanks in advance

 

[erco]

A diode.

 

[eggdweather]

A diode in series will solve your problem.

 

[Goeytex]

A diode in series is a simple solution that should work as long as the alternator signal is a sine like signal. However, do you really want to feed your logic device with a 7 volt signal? Assuming you are operating the logic device and the Picaxe at 5volts, here's how I would do it. This method will clamp the signal to about 5.2 volt positive and prevent the signal from going negative.

 

[Steevo25]

Many thanks for your replies, it worked a treat.

I have clamped the output of my 4017, that bit was working. I should have thought of a diode to stop the negative pulse. I guess only playing with electronics once in a while doesn't help retain the knowledge.