So continuing on my automated beer bottling assembly line, I'm working on a motorized scissor lift to raise and lower the bottles to the fill tubes (they need to reach to the bottom of the bottles). I've got a motor from an old 9.6v cordless drill, and a computer power supply. But of course, when I hook the motor directly to the 12v wires on the power supply, it runs for a half second and then immediately shuts off. I assume it's drawing way too much current, and the power supply shuts down as a safety feature?
If I wire a potentiometer in between, do you think that will keep the power supply from shutting off? If so, how can I tell if a particular potentiometer (like, at Radio Shack) can handle the load?
If so, how can I tell if a particular potentiometer (like, at Radio Shack) can handle the load?
You really can't use volume control type pots for voltage dropping for higher current loads like a motor, most pots are rated at 2 watts or less power dissipation. There are wire wound two terminal rheostats that are sized for the wattage they can handle. You first task is to try and determine by measurement what your drill motor draws for current. Also running a 9.6v motor at 12vdc is bound to cause it to draw more then it's design current and possibly overheat.
The +12vdc from most PC power supplies is usually capable of at least 10 amps maybe more, but again without knowing what your motor will try to draw at 12vdc it's kind of a chicken and egg problem.
Maybe someone else will have a brainstorm for you.
Does the motor have only 2 wires? Because if it has more than two it is a stepper motor.
Most probable cause of shut off is what you say, peak power to the PSU makes it shut down. The start up current of a motor is much higher than the normal current. First, try it with 5v, and if it runs ok, try a low ohm, high watt resistor in series to lower the current.
A further point about pots and power rating:-
While a pot might have a rating of say 2W that applies to the whole of the track. So if you are dissipating power between one end and the wiper then you are only using a fraction of the track and so you only have a fraction of the power dissipation. This means at the very ends of the track it is easy to blow up a pot with too much power. This is something that happened to me several times while I was learning about electronics way back in the stone age.
Of course you can't apply the fractional principal right to the end because that would tend towards zero dissipation. You need to look at the data sheet for the pot and see the minimum power ratings.
