Just for your reference: my two (good) motors free-running current is about 250mA @9V (workbench power supply). When slowing them down (hold the wheel), current goes way over 500mA.
Resistance measured on the wire leads is 1.5-2 Ohms. Bad motors are probably 30-50 Ohms… I guess this would be easier to test (no battery required).
Joep
Would you be able to share a picture of how your testing the resistance? I’d like to test mine, but as I have no experience with measuring resistance I’d have to figure all the out first.
Hi,
Connect the two motor leads to your multimeter and select the resistance range, see picture.
Note that below 10 Ohm, error of a few Ohms is possible. Make sure you have solid connections and check if the readout of the multimeter is zero when the probes are connected together (without the motor). If not, you can subtract this value from the motor resistance reading.
The resistance measured is an indication of the torque the motor should be able to provide. The supply current is dependent of the turning rate of the motor (and voltage & pwm duty cycle of the supply). And battery voltage will drop when current increases. So for a good comparison, you need supply current, supply voltage and turning rate (at lease some estimate).
Since you seem to have motor that provides insufficient torque to move, it would be interesting to know the current when they are not moving. Use your battery and measure the voltage too (don’t need to measure them simultaniously). If the current is low (with sufficient supply voltage), it’s an electrical problem. If it’s high, you have a mechanical problem. Note that high currents can damage motors, so do not block your motor for this meaurement!
Update: I had a chat with my local supplier and he told me the motor issue is a mechanical one. If this is correct, DC resistance is not usefull to detect the issue, but the no-load running current is.
Spot on!! The tutorials and getting started sections are haphazard and confusing and way too much is left out. Newbies like me find this confusing and waste hours looking for answers here on the forum. Most of these issues should be dealt with in a proper getting started section for each product.
I received my replacement motors. Running on a fresh 9V directly connected to the battery they draw ~170ma with no load. This was consistent across the 6 motors. Installed in the robot and it works as expected. Only thing I see is its a tad slower turning tight than it is left, not sure why, but will keep playing over the weekend!
Got my replacements for the motors in a bad kit here as well, and they work great. To the Makeblock team, thanks for fixing the problem.
Please help me with the motors. I sent a message to @evans_xy concerning the matter. I am new to this so please have patience. This messaging system wont allow multiple messages of the same content.
Thank you,
John
Purchased an Starter Robot Kit for my son on dec. 11 on amazon. Built kit as instructed
but no motor function. Signal is being sent from IR, lights signaling robot working, but,no movement.Checked voltage at electric motor with forward or reverse bottom pressed and get 5.75 volts ( 6 volt system ), Motors are not bound and tracts removed . Motors are defective I think .How do I get 2 replacement motors ?
