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Looking for motor specs, and how the hell should I power this thing ?

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ItsMike

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Hello,

I'm working on a rotating POV display and I got my self a DC motor from kid's toy ride-able ATV.

I assumed it was 12v operated, I measured 1Amp going through it without a load attached to it.

Anyways, I just realized it had it's model written on it:
"RS-550SH
JD020307" - Second line is really hard to read so i'm not 100% sure it says that.

Anyways, I googled for the first line and bingo - the first two matches are:
**broken link removed**
#2

But both of these have conflicting info. I tend to believe the pdf more but it has two columns of values as if two models exist and I don't know which one I have.

Anyways, how should I power it if I want to use it for my spinning POV display which weights approx 300g ? I don't need it to spin any faster than 1800 RPM.

Thanks in advance,
Mike.
 
My best guess, if you run with the .pdf file would be to measure the DC resistance of the motor. Then work from the voltage and current listed. See what comes up close. You really have to love Chinese data sheets:
Starting corrent

Ron
 
According to my unreliable cheap generic multimeter the resistance is about 0.8 ohms but I bet it's not accurate.

Anyways, any idea how should I power it for my pov display ?
 
According to my unreliable cheap generic multimeter the resistance is about 0.8 ohms but I bet it's not accurate.

That can't be right, can it? If you said you measured the current at about 1 amp @ 12 volts, then the resistance should be closer to 12Ω (R=E/I).
 
To run the motor, apply 12 volts dc, if it runs backwards, reverse the leads, if it's too fast, apply less voltage, if too slow, apply more voltage, It's a very hardy little motor.
Here's another set of spec. **broken link removed**
 
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That can't be right, can it? If you said you measured the current at about 1 amp @ 12 volts, then the resistance should be closer to 12Ω (R=E/I).

CarbonZit,

Read up on "Back EMF" of a running DC motor.

The running current of a DC motor is a small fraction of it starting/stall current. The stall current can be calculated from Ohmic resistance of the windings.
 
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Just a minor point, the performance will be much more dependent on load characteristics than the motor characteristics because the spinning POV hardware will add a lot of air drag.

The best procedure would be to build it, or a physical mockup, then test motor volts and amps to spin it at the right speed. The POV will need an optical RPM sensor anyway so you can use that to set the speed while you do the volts/amps measurements.
 
I reread you post and the motor you have, one I have also played with, runs at 1608 rpm/V and will probably work a 3 volts fairly well, but may spin faster than 1800, if 1800, if important, I'll try mine and let you know the current. I also assume that your motor came from a power wheels toy, is that correct?
Kinarfi
 
Yep, the motor came from some sort of a ride-able kid's ATV. I didn't take it apart my self so I don't know the exact model.
Anyways, I guess ill just assemble the whole display and see how fast it goes.

Thank guys.
 
BUMP.
(I didn't want to open a new thread)

I was playing around with an old LM317 to power that dc motor which unfortunately (probably) burned out (the regulator) - so I'm trying to find out why.

I managed to get 12v from it and it worked, but as soon as I connected an LED the output voltage dropped to about 6v.
Does that mean the regulator is busted ? obviously it doesn't even start the motor now.

Anyways, I don't remember which capacitors I used with the lm317 but I didn't use a protection diode (output > input protection) so that might be it.

The datasheet says the lm317 has overheating and over current protection. I was using a heat sink on it and I was running the motor for short time but undoubtedly the motor consumed all the current the regulator could provide (I measured 1.8A).
Could that be what killed the regulator ? I imagine the regulator should survive that although it must not be very healthy for it.

Another speculation to what might have killed the regulator would be the switch off of the motor (high voltage produced when a coil is switched off)
Could that be it ?

Anyways, I'll be glad for some insight of how did that regulator die and how should I protect the next regulator driving this motor ?


Thanks in advance,
Mike.
 
It could have been all of the above. If it made arcs when you turned it off it was probably the inductive kick. Add a diode across the motor as a "snubber". Or if you turned off the input it may have been the back emf higher than the supply voltage. Add the diode across the regulator. But long term you may want to use PWM.
 
It could have been all of the above. If it made arcs when you turned it off it was probably the inductive kick. Add a diode across the motor as a "snubber". Or if you turned off the input it may have been the back emf higher than the supply voltage. Add the diode across the regulator. But long term you may want to use PWM.
My bet is the motor takes way more than an LM317 can deliver and fried it, even if the LM317 is supposed be protected. Try some low ohm, 1, 2, or 3 ohm, high wattage resistors in series. If you have a 12 v supply and the motor need 2 amps, a 3 ohm resistor will cut the voltage by 6.
Kinarfi
 
It's almost definitly the back EMF from the motor when you disconnected it - de-energising an inductive load will make a large voltage spike - often in the region of 1000s of volts. Do you have an oscilloscope?
 
I have limited access to an oscilloscope, it would be a lot easier just using a diode than getting the motor the the oscilloscope and checking it.

I just wanna make sure that it wasn't over-current which killed it. I was pulling about 1.8A from it.
 
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Sorry for double posting, can't find a way to edit my last message on this thread.

Anyways I've been experimenting with the motor and different supplies.

I tried powering it with a 7.5v 1A power adapter (which was a total lie, apparently it's 12v and 3.5~ A) which doesn't have short circuit protection so it was able to run the motor with the load and all at about 600-700 RPM.

I want to squeeze about twice as that - 1200 RPM but I didn't have access to any power supply capable of that.

Recently I found an old house alarm battery - 12v 5Ah, I charged it up and tried running the motor from it.
I was holding the wires manually for a couple of seconds, I noticed the motor spin like MAD and I guess it drew so much current that I burned my finger holding the wire a bit.
I must admit I used really thin wires (AWG 20 prehaps ?) since I was assuming the current wouldn't go over 3A (for some reason) but guess I was wrong.

Anyways, I was thinking of getting a PC ATX PSU and powering it from the 12v rail. I'll probably be getting a generic PSU so I wouldn't want to draw the maximum current it can output since I'm afraid it would burn it self.

So how can I power the motor with that supply ? How can I limit the current ?
PWM will only limit the average current, I'll still have huge current spikes. Will they be unnoticeable at high frequency pwm ? if so, how high ? I can't really measure the motor's inductance can I ?

Can I use a resistor ? If I'll put a 2ohm resistor in series, it would draw 6A max but will it dissipate 18w of heat on the resistor ? Doesn't sound practical...

bah... I dislike motors : (
 
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