# variable voltage switch?

Discussion in 'Electronic Basics' started by John Doe, May 19, 2007.

1. ### John DoeGuest

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.

2. ### John DoeGuest

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

3. ### CharlesGuest

http://www.solorb.com/elect/pwm/pwm1/

5. ### JasenGuest

a buck/boost DC-DC converter

or if it's just to run a motor pulse-width modulation. (PWM)

Bye.
Jasen

7. ### JasenGuest

what's high? 10A 100A 1000A ?

what is your control signal source?

Bye.
Jasen

8. ### Guest

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

9. ### JasenGuest

laziness.

current - 2 syllables
voltage - 2 syllables

amperage - 3 syllables

electromotive force - 6 syllables
potential - 3 syllables

Bye.
Jasen

10. ### Guest

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