variable voltage switch?

Question

Using an 18 V cordless circular saw, but for a different purpose than intended. Apparently the switch is either all or nothing (makes sense IMO to help avoid binding during a cut).

If variable speed DC motor requires a large heatsink, how about just four different speeds using simple switches? Someone in the design group answered this question with a drawing but I cannot locate it in the archives.

I figure that's easy just by putting batteries in series and then dial switching in between the batteries. But that would wear the batteries unevenly. Could anyone please illustrate a four position switch that would provide zero plus three positive voltages, maybe switching the batteries to parallel so that current drain is even on all batteries?

Thank you.

John Doe · Accepted Answer

I found how to easily do that with just two positive voltages.

Is there a reasonable way to provide more than two positive voltages at the same time providing equal battery wear?

/ -------+-------/ O-------+-------------- To motor ! ! ! --- ! --- ! + ! ! ! + ! ! ! ! ! ! ! - ! ! ! - ! --- ! --- ! ! ! ! ! / ! / ! -------/ O-------+-----/ O---- GND GND

Charles · Answer

John Doe · Answer

Thanks. Are there favorite retail sources for PWMs in the 14 to 36 V high current range?

Jasen · Answer

a buck/boost DC-DC converter  or if it's just to run a motor pulse-width modulation. (PWM) Bye.   Jasen

Chris · Answer

Yup.  Try the Velleman K8004, which should handle up to 6.5 amps:at Jameco in kit form for $22.95 USD:CheersChris

Jasen · Answer

what's high?  10A 100A 1000A ?what is your control signal source?Bye.   Jasen

spamfree · Answer

Google electric scooter parts. Plenty of cheap hi amperage (sorry,current  -  why is it OK to say voltage, but considered gauche to sayamperage?) controllers of all varieties.    jack

Jasen · Answer

laziness. current              - 2 syllables voltage              - 2 syllables amperage             - 3 syllables  electromotive force  - 6 syllables potential            - 3 syllablesBye.   Jasen

spamfree · Answer

Good thought. The cause of much popular usage.

But Horowitz and Hill (Art of Electronics) claims that the use of amperage and ohmage is in the realm of the bush mechanic. I wonder if there might be an element of professional snobbishness there. jack

variable voltage switch?

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