# DC motor current rate

Discussion in 'General Electronics Chat' started by Vincenzo1309, Feb 6, 2009.

1. ### Vincenzo1309 Thread Starter Active Member

Dec 28, 2008
57
0
Greetings to all,

Is it normal to have a DC motor of load current = 5mA?
It is found in cheap remote-controlled cars.

Can I use a 9V battery, a pack which contains 6 AA batteries to power 2 of them up?

I have a motor controller which can supply 1A to each motor. Can I still use this controller to control the motors?

2. ### SgtWookie Expert

Jul 17, 2007
22,198
1,797
That's a mighty low load current.
It depends upon the motor, the load on the motor, and the voltage applied across the motor's connections.
What was the battery originally powering the motor?

Can't say unless you tell us what the original power source was.

Do you have any more specifications on the controller? A link to a datasheet or manual, perhaps?

3. ### Audioguru Expert

Dec 20, 2007
10,731
1,201
The little indoors IR-controlled helicopter toys have a very small motor that runs for 5 minutes on one charge from a 3.6V 50mAh Li-Po battery cell.
Then its current is about 4mA.

The tiny radio controlled cars used a similar small motor and battery.

I think the tiny motor will instantly burn out or fly apart if it is fed 9V.

4. ### mik3 Senior Member

Feb 4, 2008
4,846
69
The low current motor may control the steering of the RC car.
What are the specifications of the controller?
Do you have the datasheet?

5. ### Bailey45 Member

Oct 27, 2008
18
0
Assuming this is a DC brushed motor the current is proportional to mechanical load on the motor. 5mA sounds like a no-load (free spinning) reading for a small motor. This same motor under load can draw 10 - 20 times as much current.
The speed of the motor is proportional to voltage applied. The previous posts are correct in saying the easiest way to find the operating voltage is check the design it came from.
Your 1 Amp controller is fine as long as it supplies the same voltage as the original design (toy).

6. ### Audioguru Expert

Dec 20, 2007
10,731
1,201
The small RC cars costed \$10.00 about 10 years ago.
The motor was the size of a tiny vibrating one in a cell phone.
The cars weighed almost nothing and did not go very fast.
The current was very low.

7. ### Vincenzo1309 Thread Starter Active Member

Dec 28, 2008
57
0
Dear all,

Thanks for the replies.

The background is like this, I am currently building a Bluetooth controlled wheeled soccer robot. I will be controlling 2 DC motors (one for steering and the other one for forward and reverse movement) and a solenoid actuator.The solenoid actuator works for a 9V battery supply.
Therefore I bought a battery pack which can contain 6 AA (1.5V each) batteries to power my robot. I am now in the troubleshooting phase. I have got it working some time ago... then when I tried it out last week, the motor response is funny. Especially the forward and reverse movement, the motor will just turn for few seconds and then stop. Then when I lower the speed of the motor, the motor can keep on turning.

Funny thing is why doesn't the motors burn out like what Audioguru said. I am also wondering about this thought.

Below is the link to the motor controller:
http://www.parallax.com/Store/Micro...efault.aspx?SortField=ProductName,ProductName

Thanks alot!!

8. ### Audioguru Expert

Dec 20, 2007
10,731
1,201
We are guessing at the max allowed voltage for your motors.
We are guessing that they came from a cheap \$10.00 toy car not a \$50.00 one.
Who knows when the motors will burn?

9. ### Vincenzo1309 Thread Starter Active Member

Dec 28, 2008
57
0
Hi, yes, it is a cheap \$10.00 toy car.

So you are saying that if the motors are made to run at maximum speed for prolong period of time, the motors might just burn off?