Short question topic

[MrCrowley]

I wonder if you can wire the battery to the mains while it is being used by the motor. I assume the battery charger has a low amp output but gets away with it by being able to build up the power over long periods of time and allowing the motor to draw what it requires in a very short amount of time.

Which reminds me, I should add that I used a cellphone charger on my fridge compressor to power a computer fan using the mains power, not powering the actual compressor with the transformer + rectifier.

[Gun Freak]

A 12V compressor probably draws more current than this dinky motor... Besides I don't need it to run ridiculously fast, I was just thinking about making a little micro wood lathe with it.

[Zeus]

Heh, guys, please don't try running DC motors on any form of AC. You'll let out the magic blue smoke, and as we all know, electrical devices need the blue smoke inside to work.

Warhead, down here in Australia and New Zealand, we use 230/240V for everything, if we need to run a bigger appliance, we use a 15 amp outlet.

GF, hook it up to a car battery, doesn't matter if it's still in the car, it's safe. Don't be afraid of car batteries, just because they can dump a shitload of current, doesn't make them dangerous. If it runs fast enough, then you need a high current plugpack/wallwart. If you ask at an electronics store, they'll help you.

Don't let them sell you a large power supply, you won't need it, and you'd be wasting money.

If you want to buy one on Ebay, here's a perfect one for you.

[Fnord]

just because they can dump a shitload of current, doesn't make them dangerous.

But do be cautious if you have any open cuts on you hands. Human skin is a good insulator when it's in the way, but otherwise you're just a sack of water. You could potentially* die from a 9-volt battery if you touched the terminals with bloody fingers.

*terrible pun, please ignore

[Gun Freak]

I don't exactly have any spare car batteries lying around

You say not to run a DC motor on AC, I know that, but don't these wall chargers convert it to DC? On my chargers it says "INPUT 120VAC OUTPUT xV xA"

[Fnord]

Pretty much ANY wall charger will have a DC output. I've only encountered one in all my life that was AC.
It would be a good idea to know how much current this thing draws before buying/cutting up a transformer. Do you have a multimeter?

[Gun Freak]

That's what I thought. And yes sir, I do have a brand new multimeter! Got it at a craftsman Christmas sale now how do I use it

Edit- ok I just put the multimeter on 9V DC and it showed 8V and change. When I put the motor on it, it showed a little under 4V. So does that mean the motor draws about 4.5V?

[Fnord]

It just means the voltage is dropping off that much due to the current the motor is pulling. It's like how the pressure in your water pipes will drop when you turn on the faucet.

To get a measure of current draw, set your multimeter to the "10Amp" or similar dial setting and plug the red probe wire into the "10amp" socket (if it has one).

Connect one motor wire to the battery, and the other motor wire to one of the multimeter probes.
Touch the bare battery terminal with the other probe, and you'll make the meter part of the circuit, allowing it to measure the current going through it.

If your meter only has a low-amp setting like 300mA, don't try to use it, you'll probably pop a fuse or fry something.

[Gun Freak]

This is the one I have:
http://www.sears.com/shc/s/p_10153_1260 ... 000P?mv=rr

10Amp DC right?

[Fnord]

Yeah, that'll work.

If the current readout goes above 10Amps, disconnect it. My HF junker meter will go a little higher but you'll blow a fuse if you hold it there for too long.

[Gun Freak]

Hm, this isn't working out, no matter where I put the wires, a positive always ends up being paired with a negative and nothing happens...

[Fnord]

You're trying to do this? That's what it should look like

The meter polarity is not important. If you hook it up backwards it'll just read negative current.

[Gun Freak]

Yep that's how I'm doing it. The motor doesn't run. It's like the meter is messing up the circuit.

[ramses]

Make sure the test leads are in the correct ports of the meter.

There is usually one specifically for current.

[Gun Freak]

Ah, ok I tried changing the positive lead from the meter to the port in the middle and I got a reading of -.62. So... What exactly does this mean?