off-the-shelf variable output AC/DC switching power supply?

Question

i am trying to control the voltage to a DC brushed motor. it draws about 1.5A at full load. its working voltage is 12V. i know that there are many ways to do this, but I would like to do it with an off-the- shelf, variable output (controllable with a external pot) switching AC/ DC power supply. by variable i mean 0 to 12V.

anyone know who might sell one of these? ive been looking about but they all seem to be fixed output or only adjustable a few percent with an on-board pot.

OR:

if there is an IC from linear etc... with a datasheet giving part numbers for an equivalent circuit, that would work

whit3rd · Accepted Answer

Lots of switchmode control chips can generate a variable-duty-cycle square wave (a one-op-amp triangle wave generator, a comparator, and a potentiometer is all it takes). Add a switch transistor and diode to the (presumably inductive) motor and it's done.

Mostly, if you need 1.5A, you don't want to use an all-in-one circuit. If you really are starting with AC, though, a variable autotransformer and rectifier might be simpler.. don't go over the 12V limit, or disregard the shock hazard if you go that route.

acannell · Answer

oooh! neat-o idea i like the sound of it. couple questions...

so the current for the motor passes through the calibrated resistor? you cant mean that right? unless its really low value?

so the voltage at the base stays fixed, but its pwm modulated? so i turn off-and-on a certain set voltage (which sets my current pulse) at the base?

off-the-shelf variable output AC/DC switching power supply?

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