Measure Pulse Width / Duty Cycle of an Injector to drive a pump

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Thread Starter


Joined Apr 8, 2012
Hi All,

First post here so apologies if I've started this thread in the wrong section. I would like some advice and programming help to help me build a device that will measure the Pulse width / duty cycle of a car injector. This signal then needs to be either converted into a steady or pulse width DC current that will drive a geared motor that will drive a mini peristaltic pump.

Specifically, I have a prinns LPG system installed on my car but the system that delivers the Valve Saver fluid (flashlube) relies on the vacuum of the inlet manifold and a needle valve. The flow is very inconsistent and I could also do with some sort of feedback loop in the car to keep an eye on the flow (a simple flashing light perhaps)

I'm an electronic hobbyist up for a challenge. I've read various posts and messages on the internet around this subject and feel it's within my grasp but need some help putting it all together.

Talks about using a comparator circuit to create a nice clean square wave.

Is a PIC controller that I think would provide the necessary speed and control all in one. I'm very familiar with VBA programming and so feel confident in reading up on and understanding PIC language if I'm given some pointers.

I've also done some preliminary analysis on the pulse that the injectors receive and have attached an example. The portion that is of interest is close to the 8th horizontal division which goes from 15v to about 45v peak. The rev range is 0-6k rpm.

With this info, please can anyone help?

Many thanks in advance




Joined Mar 24, 2008
The owners and administrators of the All About Circuits forum Administrative Team has elected not to host discussions of automotive electrical system modifications/enhancements due to safety concerns, the potential of legal ramifications and the possible circumvention of vehicle regulations at the state and federal level.

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