Hi guys I have a pololu 4744 12v motor connected to a 3 amp speed controller and a 5a power supply.however when I turn the motor on via speed controller slowly it will turn but if I turn up everything heats up and light on controller flashes.I have measured amps.I get between 3.5a and 6 with no load on motor sometimes it spikes to 10. The motor seems real tight I can not turn by hand.is this a faulty motor
Try disconnecting the motor completely from the controller to see if you can turn it. A good motor will be very difficult to turn if it has a short circuit across it.
If it turns freely try connecting it directly to the power supply.
If it works OK directly from the power supply the controller board is faulty.
Exactly which controller board do you have. It may be as simple as a shorted flywheel diode but if that is the case the H bridge (if that is the controller type) may be damaged now.
Disconnected I can not turn either.it was like this out of the box
Just looked up that motor specs. It has a 70:1 gear box on it so will be pretty impossible to turn by hand.
Try connecting to the power supply directly. Might be a good idea to measure the current at the same time.
A quick look at what to expect.
It’s definately not a problem with the controller as that is working fine with another motor.how would I test for a short in motor
With a multimeter. With a stall current of 5.5A I would expect a coil resistance of about 2Ω although this would be variable depending on the position of the brushes at the time.
The direct power test should tell all but be quick as the power supply might not like it for too long. The use of a current limited power supply would be ideal here but you might not have access to one of those.
PS: If you have it mounted you did see this on Core description did you not.
Warning : Do not screw too far into the mounting holes as the screws can hit the gears. Pololu recommend screwing no more than 3mm (0.12") into the screw hole.
Bob is absolutely right, a multimeter is definitely the best way to go for testing this one out.
If you haven’t used one before check out this SparkFun video on YouTube: https://www.youtube.com/watch?v=SLkPtmnglOI&t=1s. It’s got some great info and tips to help you get started.
We’ve also made this video on Ohm’s Law which could be helpful-----> How To Use Ohm's Law In Electronics - Video Tutorial Australia
As the pic shows on the web page; 3 screws to remove the gear box and cover from the motor.
The small motor gear should rotate freely and you can visually examine the gear box for damage to the gears. You can also see if the motor turns nicely when power applied.
As you say, another motor works ok; I would say this one is probably stuffed. Either motor or gearbox.
I had a similar problem with a small servo, one of the plastic gears had lost a couple of teeth.
But in your case it would take a lot to damage metal gears.
PS The recommended brackets shown on the web page have screws of the right length to fit and not damage the gears.
Confirm that the motor, speed controller, and power supply have adequate ventilation and cooling. Overheating components can malfunction and lead to unexpected behavior.
Hi thanks for suggestion.i had all components hooked up in open air same result
hi @bobby207075 - some pictures of what’s going on will be really useful for everyone trying to help. Can you provide pictures showing as much detail as possible?
It definitely sounds like something is amiss - these motors should only draw <500mA with no load.
That was my thought.i am away for a few days.but the guys know about it and are going to test a new motor once they get in stock.i will update when home
Have you tried the motor connected directly to the power supply. You have not said. preferably with a current meter connected to monitor current.
I have not tried this as of yet
Opening it up and visually checking the gears would be my first path.
As it has already shown excessive current draw I would be reluctant to apply any more.
Once separated into gearbox and motor things might be more obvious.
You and I and many others who try to help people on these forums have decades of experience.
We post only valid information and try to guess the experience level and understanding of those who we are replying to and reply at that level.
Sometimes I find these forum posts very frustrating.
Haha I wish I only posted valid information all the time
That would be my next suggestion. I did say to carry out the direct connection test very quickly to minimise damage.
If bobby is not confident to do this then his input would have to stop there or get someone else to look at it.
I agree that once separated it would be a fairly simple task to investigate the motor and gearbox separately. He has not said (although asked) if the unit has been mounted or not as long screws interfering with the gear box are a possibility. There is a quick, cheap and cheerful method of checking the motor. Spin by hand then short the connections together and judge how much harder it is to turn the motor. A good motor will be very much harder to spin when shorted.
You and me both. I have often (on this Forum) likened getting correct accurate information to pulling teeth. Almost impossible some times.
I think NO information is better than grossly confusing or misleading information.
I have nit been home last few days to try suggestions.i should b home this afternoon.
Robert these issues are there mounted or unmounted same result
OK. If the motor still does not turn when connected directly to the power the gear box will have to be removed to pin down the problem. This could void any warranty that applies so as the motor is probably available separately I think getting a gear box would be a bit harder.
With warranty in mind if the unit is still faulty I would suggest pursuing a replacement under any warranty arrangements that exist.
Please monitor the current while doing this check and remove power immediately if too great. There will be a little bit of extra inrush current at first but should settle to the no load figure. About 0.2A. If jammed it should not go much above the stall current of 5.5A but if it anywhere near this remove power immediately.