PWM - Huh?

[Bennett]

I have tried doing my own research on them but I can't seem to understand exactly what they are, or what they do to help. I'm not lazy (or a good speller, sorry) it just all seems to go right over my head. Can someone give me a quick "PWM for Dummies" speech? in laymen's terms, if possible

[keiththevp]

As an hho cell runs it generates heat and warms the electrolyte. This causes a lower resistance in the water therefore allowing a higher draw of current. So if you start your cell at say 10 amps after eight hours it could easily hit 18-20 amps. So the PWM basically turns the power on and off at a high frequency in order to keep the average amp draw at your desired setting. So in the same previous scenario you could set the PWM for 10 amps and it will stay there, instead of slowly increasing to 18-20 amps. Hope that helps that is about as basic of a description as I can make.

[Bennett]

Thank you! that makes perfect sense, I can't believe I didn't see it before.

[Stevo]

FYI: On a highly a efficient reactor (not just talking about mmw here), you probably will not need a PWM. There are lots of factors to be concerned with here, so IMHO building the most efficient reactor possible (e.g. partial zero or zero current leakage) is the way to go. PWM units use some energy to operate (some are more inefficient than others). Some claim that pulsing and frequency increase efficiency, but I really doubt that as whatever "efficiency" is gained would be swallowed up by the PWM's power consumption.

[Farrahday]

As an hho cell runs it generates heat and warms the electrolyte. This causes a lower resistance in the water therefore allowing a higher draw of current. So if you start your cell at say 10 amps after eight hours it could easily hit 18-20 amps. So the PWM basically turns the power on and off at a high frequency in order to keep the average amp draw at your desired setting. So in the same previous scenario you could set the PWM for 10 amps and it will stay there, instead of slowly increasing to 18-20 amps. Hope that helps that is about as basic of a description as I can make.

Actually this is not what a PWM was designed to do!

Many people are simply using a PWM to control the power going into an electrolyser, and while it may have merits being employed in this way, this is not the reason it was designed.

Does anyone know of Dave Lawton? He built and provided the schematics for a PWM (Pulse Width Modulator D14) that was used not to simply control the power input into a cell or electrolyser, but in order to try to enhance efficiency. A PWM has a variable frequency and a variable gating frequency. Simple control of the power to an electrolyser does not require both these facilities and in reality a much simpler cct could be employed to do the job.

People seem to have completely forgotten what a PWM was designed to do. Think, Puharich, Meyer, Lawton, Ravi, Naudin, amongst others!

And in fact as Stevo touches on above, when used to simply control power to an electrolyser, it actually does use power itself and so reduces overall efficiency. A correctly designed, standard brute force electrolyser is more efficient without the use of a PWM!