Backyard Aquaponics
A place to discuss aquaponics

I pulled some interesting bits out of an old digital point and shoot, including a couple of motors.

There are no Id marks or manufacturers name or anything.

The device is powered by 2 x 1.5 volt batteries, so I'm guessing the motors are 3 volts, but is there some way to be sure? ie with a multimeter or something?

Put 1.5v on them and see what happens. Then if they're not spinning fast enough, put 3v on them.

I was hoping I might learn how to work such stuff out.

I take it that means there isn't a way.

I was hoping for some nice equation like resistance times pi over underpant = voltage ... something like that.

Google tells me to keep putting more juice in until it gets hot. I might try that.

Cameras have some interesting bits inside, including a very nice linear moving thing to focus. The focus lens has a nut mounted in it's bracket, and a little motor has a length of threaded rod so the lens moves up and down it.

The smallest of the motors, the one doing focus, has four wires. does that mean it's probably a stepper motor

Probably.. Or has some position feedback. Try google that too...let us know

We once had to do something at tafe to measure estimated voltage of a motor.
You need a Gauss meter and an inductance meter and you do a heap of simple calculations.
Some where in there we also had to turn the motor at a known speed and take readings.
After teaching us the lecturer told us it was a waste of time as both meter are notoriously inaccurate and you are better off using the method you mentioned

Actually come to think of it, if you put your multimeter on the motor pins and connect the motor to a hand drill you can probably measure the out put voltage generated by turning it.
That would be close to required voltage.

Just follow how the batteries are wired. If it goes for positive to negative, then to positive, and then back to negative it is a 3 volt motor. If it goes from negative to negative, and the other wire goes from positive to positive then it is a 1.5 volt motor.

We once had to do something at tafe to measure estimated voltage of a motor.
You need a Gauss meter and an inductance meter and you do a heap of simple calculations.
Some where in there we also had to turn the motor at a known speed and take readings.
After teaching us the lecturer told us it was a waste of time as both meter are notoriously inaccurate and you are better off using the method you mentioned

Actually come to think of it, if you put your multimeter on the motor pins and connect the motor to a hand drill you can probably measure the out put voltage generated by turning it.
That would be close to required voltage.

The wiring at the batteries would make it 3v.

Do designers always use full voltage at a motor? I guess it would be inefficient to do anything else.

I have so much stuff to learn.

from here...

http://www.avrfreaks.net/index.php?name ... c&p=962463


jwatte says ....

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"A motor coupled with a position sensor and a control system is generally referred to as a "servo." "
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Then goes on to say some other interesting stuff.

my search has taken me to servos to leadscrews and a linear motors and then maglev

All roads lead to maglev.


This little motor looks like it isn't sophisticated enough to do feedback. (Based on nothing) It doesnt really matter for this motor, I was wondering in a more general way, how to go about identifying something's required voltage.

I wonder if perhaps it just connects to different pins of a chip so it can be controlled forwards and backwards as required. Come to think of it, that's probably what I'd need to do to make my solar controller.

Always, maybe not. But it is efficient to do so. Remember the 1.5 volt batter will actually put out probably closer to 2 volts when new.

The rated voltage is not what you need to worry about as long as you stay in reason. Your real concern is how much current you are going to draw. Current draw will depend on voltage and load (resistance to turning). Also note that a motor might be OK drawing 2 amps for 30 seconds but might burn out if run for 60 seconds.

werdna mentioned turning it with a drill, that will tell you the kv of the motor. If you have to turn the motor 1000 rpm to get a one volt output you have a 1000 kv motor which should turn 3000 rpm with a 3 v input.

Here is something you might like to read:

http://www.southernsoaringclub.org.za/

( Articles by SouthEasterners.
Electric Motors - part 1-5)

With 4 wires its probably a small stepper motor. That way the camera will move a given distance of focus on each pulse.

Since reversing the voltage normally reverses direction on dc motor I doubt it is that.

So true

I nearly ordered 100 rare earth magnets when we were hinting at maglev's, now you have got me interested again

do it

I'm still in the process of reading this in 2 minute bites between doing everything else. There's some good stuff in there. Well explained.

Thanks for the link.