go_away

Author Topic: DC Motor only runs .5 seonds and stops, then starts again  (Read 17837 times)

0 Members and 1 Guest are viewing this topic.

Offline crivensTopic starter

  • Beginner
  • *
  • Posts: 5
  • Helpful? 0
DC Motor only runs .5 seonds and stops, then starts again
« on: March 02, 2015, 10:10:06 AM »
Hi.  This should be an easy solution, but I'm very electronically illiterate.  I'm not building a robot, but I'm using a DC motor that I bought from Servocity for my project.  I wired the 12v motor directly to the 12v DC power supply; however, the motor will run for approximately .5 seconds and then shut off for .5 seconds and then cycle through again, effectively causing the motor to pulse.  I just need it to run constantly.  Since there are no electronics between the motor and the power supply and there are no electronics on the motor itself, I'm not sure what is happening.  The specs on the motor are: 
Operating Specifications:
Operating Voltage Range: 6~12VDC
Rated Voltage: 12VDC
Rated Load: 3.2 kgf-cm (44.4 oz-in)
Operating Temperature: -10 ~ +60C
Max No-Load Current: 0.52A
No-Load Speed: 437 RPM
Min. Stall Torque: 22 kgf-cm (305.5 oz-in)
Max. Stall Current: 20A @ 12VDC
Dielectric Strength: 250 VAC
Motor Brush Type: Graphite
Output Power at Max. Efficieny: 13W
Gear Type: Planetary
Gear Ratio: 19:1
Bearing Type: Dual Ball Bearing
Shaft size: 6mm (0.236)
Net Weight: 330g (11.64oz

The Power supply specs are:
Input Voltage: 100-240Vac
Input Plug: USN
Case: Wall Plug in
Frequency: 50/60Hz
Input Current: 0.8A max
Output Volts: 12 VDC Regulated
Output Current: 2500 mA
Power Rating: 30 Watts
Dimensions: 88 x 58 x 48mm (Case)

Any help on an affordable way (less than $20) to keep the motor running continuously would be appreciated.  Thanks.


Offline crivensTopic starter

  • Beginner
  • *
  • Posts: 5
  • Helpful? 0
Re: DC Motor only runs .5 seonds and stops, then starts again
« Reply #1 on: March 02, 2015, 10:14:16 AM »
I forgot to include that the problem exists without a load on the motor.  The motor has 305.5 oz-in torque.

Offline pkott716

  • Beginner
  • *
  • Posts: 4
  • Helpful? 1
Re: DC Motor only runs .5 seonds and stops, then starts again
« Reply #2 on: March 02, 2015, 02:31:33 PM »
Have you tried running it from a battery instead of a power supply and see if the problem continues? Sounds like a power supply problem to me.

Offline mklrobo

  • Supreme Robot
  • *****
  • Posts: 548
  • Helpful? 14
  • From Dream to Design at the speed of Imagination!
Re: DC Motor only runs .5 seonds and stops, then starts again
« Reply #3 on: March 02, 2015, 03:37:31 PM »
 :) Hello!
I would agree with pkott716, with the power supply problem. I would try a battery,
and if that did not work, I would email ServoCity about the issue, to make sure they
sent me the motor that I ordered, and that I did not expect this action form this motor.
Keep me posted....   :) :) :)

Offline bdeuell

  • Robot Overlord
  • ****
  • Posts: 189
  • Helpful? 15
Re: DC Motor only runs .5 seonds and stops, then starts again
« Reply #4 on: March 02, 2015, 05:40:45 PM »
does the power supply have overload protection?

When you start a DC motor its initial speed is zero and because current draw is inversely proportional to the speed it will start drawing the full stall current. Under no load this current draw will rapidly decrease as the motor accelerates to the no load speed. however seeing as your power supply is only rated at .8A and the stall current is 20A I would not at all be surprised if you are overloading the power supply. The .5 second run time may be the time it takes the power supply to trip out and then it automatically resets after some time and the cycle repeats.

It is possible there is something else going on but with the given information I think that power supply overload shutdown is the most likely.

Connecting the motor to a battery or higher wattage power supply would both be good tests. Your current power supply is probably significantly underpowered if you plan to put any load on your motor.


Offline Billy

  • Robot Overlord
  • ****
  • Posts: 132
  • Helpful? 2
Re: DC Motor only runs .5 seonds and stops, then starts again
« Reply #5 on: March 02, 2015, 11:51:45 PM »
It is possible there is something else going on

Nope. I'm pretty sure you nailed it.

Offline crivensTopic starter

  • Beginner
  • *
  • Posts: 5
  • Helpful? 0
Re: DC Motor only runs .5 seonds and stops, then starts again
« Reply #6 on: March 03, 2015, 06:00:24 AM »
Thanks for the input.  I don't have a battery to test it with.  Maybe I could wire up a 18v cordless drill battery to it, but that is more volts than the motor is rated, so that might not be a good idea.  However, I did try other 12v power supplies that I have laying around and I get the same problem with two other power supplies.

So, I've looked around for AC/DC power supplies with enough amps to run my motor, and I can't find any with anything near 20A.  I won't have a significant load on the motor.  It's just hooked up to a pulley with a rubber belt that turns a simple mechanical counter.

Is there an affordable solution to my problem?  Maybe a transistor or something that I can wire in-line to increase the amps temporarily just to get the motor up to speed?

My other idea was to put a thicker gauge wire from the power supply connector to the motor (currently I'm using pretty thin wires).  Would that make enough of a difference?

Thanks again for your input.
« Last Edit: March 03, 2015, 07:35:57 AM by crivens »

Offline mklrobo

  • Supreme Robot
  • *****
  • Posts: 548
  • Helpful? 14
  • From Dream to Design at the speed of Imagination!
Re: DC Motor only runs .5 seonds and stops, then starts again
« Reply #7 on: March 03, 2015, 07:35:59 AM »
 :) Hello!
Worst test case scenario; Use your car battery.(vehicle off)
That should have enough current to power it, but do not leave
it on for a long period of time,
just enough time to test the starting/stopping
interval. 20 Amperes is a right good amperage for a robot motor.
Good luck!  ;D ;D ;D

Offline Schlayer

  • Full Member
  • ***
  • Posts: 57
  • Helpful? 3
Re: DC Motor only runs .5 seonds and stops, then starts again
« Reply #8 on: March 03, 2015, 08:05:36 AM »
20A is really quite a lot of current to come from anything but a battery... I could some things that claim to be 12V 20A power supplies, but these all seem to be solely intended to power LED strips, not motors, whose current draw changes rapidly. I would be concerned about damaging the power supply, but here's one such link I came across.

I would probably have to agree with the other people here stating that a battery is a safer option.

Offline crivensTopic starter

  • Beginner
  • *
  • Posts: 5
  • Helpful? 0
Re: DC Motor only runs .5 seonds and stops, then starts again
« Reply #9 on: March 03, 2015, 09:01:06 AM »
Hmmm.  Well, I need the motor to run continuously, without the hassle of charging a battery because I'm using the motor in a clock-like mechanism. I will try connecting the motor to a car battery tonight just to eliminate any doubt about the problem. 

Schlayer, thanks for the link.  You said you would be concerned about damaging the power supply.  Can you explain?  Looking at the description of the one you found, it says it has "smart device surge protection for Shortage Protection, Overload Protection, Over Voltage Protection."

Does anyone else have any input on whether or not that power supply will work?

Here are the specs on the power supply Schlayer found:

1. Input Voltage: 115V/230VAC(90~132VAC/180~264VAC)
2. Output Voltage: 12V DC
3. Output Current: 0~20A
4. Protection: Shortage Protection, Overload Protection, Over Voltage Protection

Offline Billy

  • Robot Overlord
  • ****
  • Posts: 132
  • Helpful? 2
Re: DC Motor only runs .5 seonds and stops, then starts again
« Reply #10 on: March 04, 2015, 01:12:03 AM »
Does anyone else have any input on whether or not that power supply will work?

Here are the specs on the power supply Schlayer found:

1. Input Voltage: 115V/230VAC(90~132VAC/180~264VAC)
2. Output Voltage: 12V DC
3. Output Current: 0~20A
4. Protection: Shortage Protection, Overload Protection, Over Voltage Protection

Please note it says 12V, 20amp 120W. 12V at 20A is 240watts, so there is something off about that.
Overload protection could mean many things. Some will recover from overload as soon as the overload condition is removed, some require the load be disconnected or the supply power cycled.

There are options for reducing the current when you first connect the motor. A resistor in series with the motor will limit current and if the load on the motor is low enough it may be a permanent solution. You can also use an in-rush limiter which has a high resistance when cold and low when hot.  http://en.wikipedia.org/wiki/Inrush_current_limiter

Offline crivensTopic starter

  • Beginner
  • *
  • Posts: 5
  • Helpful? 0
Re: DC Motor only runs .5 seonds and stops, then starts again
« Reply #11 on: March 04, 2015, 06:13:06 AM »
OK.  Problem confirmed.  I wired the motor to my car battery (thanks mklrobo) and it ran without a hitch, so I guess my only option is to get a new power supply or a smaller motor.  Thanks everyone for your input.

Offline Schlayer

  • Full Member
  • ***
  • Posts: 57
  • Helpful? 3
Re: DC Motor only runs .5 seonds and stops, then starts again
« Reply #12 on: March 17, 2015, 07:41:57 AM »
   There are probably a lot of geared motors with large amounts of torque at the expense of speed that can run at lower than 12V. I found one motor with a massive gearbox mounted to it that takes just 5V DC. In hopes of using it for a display stand turntable, I was able to solder a switch to it and then splice on a regular old AC/DC converter wall socket from an unused cell phone charger directly to the switch and motor contact. It works like a charm and has so much torque I cannot physically stop it from turning with my bare hands, which is pretty good for something that takes less than half an amp of current! It only turns at like 10 RPM, but for my purposes that was fine. What kind of speed requirements do you have for your project?

 


Get Your Ad Here