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PWM generator

flippineck

Sep 8, 2013
358
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Sep 8, 2013
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I need to come up with a cheap and simple Pulse Width Modulation square wave generator with the following parameters:

Power source: 12V SLA battery
Data low: adjustable (trimmer ok) 0V thru +3V
Data high: adjustable (trimmer ok) +5V thru +12V
Frequency: adjustable (trimmer ok) 50 -100 Hz
Duty cycle: adjustable via a decent knob, 20% thru 80% on a linear dial or slider

Signal distortion not too critical I don't think (exact figures unavailable)

This is for test-feeding a control pin on a smart charge style, alternator.

Given that I have limited test equipment and only fairly basic construction tools at the moment, what would be the simplest, easiest and cheapest way to approach this? Assembling basic components, soldering, basic multimeter testing all possible here but I have no oscilloscope or frequency counting hardware at the moment.

Best I could do to get a sense of what it's producing would probably be an earphone to listen to the output

Is there something ready-built available that would suffice, maybe with some kind of basic readouts?

Thanks for any ideas. Here's the post I'm working from: http://www.msextra.com/forums/viewtopic.php?f=131&t=58716
 

kellys_eye

Jun 25, 2010
6,514
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Jun 25, 2010
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6,514
From the link you provide I see no reason or requirement for the need to adjust data low/high.

Frequency and duty cycle, yes. At a fixed 12V (with optionally a 5V output) will be enough.

There are many such schematics with the appropriate component calculations available from a simple Google search. The 555 timer device can do all that.

Google 555 PWM schematic and check out the many results.

https://www.google.co.uk/search?cli...f-8&gfe_rd=cr&dcr=0&ei=pd6RWofhCY6Gtgfjuru4Aw

But other than a dial with 'min' and 'max' on it you won't get any sort of decent calibration without resorting to an oscilloscope. Fortunately, at the frequencies you're referring to, you can use a software oscilloscope that runs on a PC:

https://windowsreport.com/oscilloscope-software-pc-laptop/
 

WHONOES

May 20, 2017
1,217
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May 20, 2017
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In this day and age, even cheap multimeters often have a frequency meter built in.
 
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