dptdpt:
Thanks Cr0sh! I really doubt that the motor was custom made. The ball machines don't do high enough volume to warrant custom parts, and I would think there would be dozens (hundreds?) of off the shelf motors that would meet its needs. It just has to spin a wheel, wouldn't ever stall during normal use, and has a very low load. But what do I know - I'm new to this electronics stuff.
I don't mean "custom made" - rather, some manufacturers of motors (and other components) will allow a buyer (in a large enough volume) to have custom numbers stamped onto the part being sold (instead of a standard reference part) to allow for stock control by that buyer in their own system. Other times, manufacturers can allow a buyer (again, provided the volume is large enough) to specify certain particular "options" (most available via the datasheet, but again - if the volume is large enough, slight customizations are allowed as well) to get a slightly custom motor; in this case, the number may again be stamped onto the motor to reflect this customization at the client's request, or simply to make it clear that it isn't a standard part made by the manufacturer. In both of these cases, these are typically referred to as "in-house numbering" - you will find this on a lot of typical "surplus" parts, and trying to figure out what a part really is can be a great frustration.
That said - I do agree with you that if the volume was low enough, or if the application is generic enough (and this seems to be the case here - though I am at a loss at exactly what you mean by a "ball machine"?) - then such semi-custom parts likely wouldn't be needed. You could then be looking at something completely different - a case where the manufacturer, for whatever reason (though typically because of a sale, merger, or just to "differentiate" the product and freshen it up) - decides to completely change the part numbering scheme. I've seen this before on motors - notably the Pittman line; the brand and company have been sold/merged more than once over the years (from what I could gather - but I am not an expert here), and certain motors from the 1980s which are still made today have a completely different part number today vs then. Generally, the only way you can get information on these older parts is to get in contact with the company and/or a local sales distributor for the company - and hope/pray that they created and kept a cross-reference (which in most cases they don't).
dptdpt:
If you could point me to a tutorial on how to control motors and what I need to figure out about its characteristics so I can control it without destroying it, I'd appreciate it.
Well - google "How to measure DC brushed motor stall current" and I am sure you will find something...
dptdpt:
But regarding measuring the current, can't I use a multimeter for that? I have a good Fluke multimeter that can do current, max, avg, etc... Like I said, I'm new to this stuff, but if there are situations where you need to make a "shunt resister" (new term to me) to measure current, instead of using a multimeter, then I understand less than I thought. Or maybe you were assuming my multimeter didn't do current...?
The typical way to measure a motor's current consumption (and you will learn this as you google) is via what is known as a "pony brake" - this is basically taking the motor, mounting it solidly so that it can't move (period), then clamping the shaft so it can't move (or can just barely slip - in a real setup, the force on the shaft can be varied to simulate different loads - but this isn't so practical "at home" - but there are ways to do it; some easy, some interesting, some difficult). All of this needs to be mounted very solidly.
Then you use a power supply capable of supply the voltage needed and at the minimum the same amount of current or more that the motor will use under this heavy load (which may be a "stalled" load - that is, a load so great the motor can't turn, and thus it uses maximum current).
Since you don't know the current this motor will take under this condition - it very well may be larger than what your meter can handle (most meters can only handle 10-15, maybe 20 amps for very brief periods - under a couple of seconds - at least via the leads; those with clamp-on current measuring can sustain much larger currents of course). So - if you are running the current through those leads with the meter inline - and the current needed is larger than what the meter can handle, then pop goes the weasel and you're out a meter.
By using a shunt, you are only limited by the maximum amount of voltage the meter can show, and since you are actually measure the voltage drop across the resistor, then as long as your meter can show you the supply voltage, it will work to show you the lesser voltage.
All of that said - a pony brake on a motor can be a bad thing - if things are mounted very solidly (or you misjudge the power of the motor) - you can have a dangerous situation on your hands. If the shaft is locked solid, and you power the motor for more than a second (and maybe even less!) - you can end up with a blown or damaged motor, power supply, or maybe even a fire situation (which is why it is better to allow some shaft slippage if possible, then add on a percentage). Suffice to say, also, that you can't measure a gear-motor this way - only the base motor - because in a gear motor, you can easily break gears and whatnot under such a stall condition (I did this once with a Pittman gear motor accidentally - which is how I came to know that my part number wasn't standard - and I did get in contact with a local sales rep - but they wanted to sell me a minimum of 50 of those steel gears at $7.00 each - for a motor I had paid $10.00 for as surplus).
So - there are other ways to measure the stall current - some indirect, and some relying on slightly specialized tools (like a way to sample and hold an initial measurement from startup of the motor - because a motor at rest is -at- stall current conditions, and so if you can measure that instantaneous application of current to the motor, you can get a good idea about the stall current needs). As you google, you will find out about some of these other methods - some of which can be easily done with motors at home - others you can't without spending more money than it is generally worth.
One other simple method I have head about to measure the current of an unknown motor, is to measure the resistance of the windings while rotating the shaft, noting the resistance values as they change, and getting an average (well, some say an average, others say take the lowest value) - then use that resistance measurement with your supplied voltage amount to calculate the current; I am not sure if this really works, or what current it is supposed to measure (running current, loaded current, or stall current - or something else).
