Electronics Geniuses Here Please!!!

godinman

godinman

godinman

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26 Feb 2007
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Ok, so I am trying to make my own fuel injector cleaning rig, it's a pretty simple task mechanically, but I am a bit stuck on the electronic side.

Basically I am after a square wave signal generator, hopefully with pulse width modulation, so I can keep them open for varying amounts of time.

I've found something here - http://www.rmcybernetics.com/projects/DIY_Devices/homemade_signal_generator2.htm

But it's not quite what I am after, anyone got any pointers? I'm sure it's actually a fairly simple 555 timer circuit, but I am lacking knowledge....

Obviously I'll have this switching a few transistors to get the voltage/ampage up, and the probably parallel up the injectors so they all switch at the same time.

Thanks for any help:)
 
That's what I'm looking for!! Brilliant, now I just need to convert that into a physical circuit lol.

I should be able to change the pulse speed, and the pulse width if I change R1 for two variable resistors, with a diode infront of each of them, meaning it charges C1 through one of them, and discharges through another, the value of each resistor varies the rate of charge/discharge changing the speed of oscillation.

Or am I wrong?

Thanks mate:)
 
R1 is already a variable resistor. It's a potentiometer with the charge and discharge diodes wired in to either side. R1 will control the duty cycle of the waveform. To change the overall frequency of the waveform you need to change the overall value of R1 or the value of C1 using the formula Frequency = 1.44 / (R1 * C1)

squarewave.gif
 
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Oh I see! That'll do it nicely I think. So changing r1 will change the frequency as well as the duty cycle? That'd be fine, as I'm only after a cleaning/test cycle.
 
As it stands adjusting the potentiometer R1 only changes the duty cycle. To adjust the frequency you would need to change either the value of C1 or the value of R1 (i.e. the actual pole to pole value of the pot, not simply by adjusting the wiper)
 
I think I'm going to have to do a bit more reading! I'll work out the required frequency and go from there.

Thanks a lot, I may well be back asking more questions.:D
 
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