Ammeter

[Gobiner]

Alot of teams have talked about monitoring the amperage in their motors. I want to know how you would do this. I'd assume you have an ammeter in series with your motor and somehow feed that into the RC. Thanks in advance.

[Al Skierkiewicz]

There are a variety of ways to do this. When teams are talking about monitoring current, it usually refers to a simple procedure to check during construction that all motors are drawing current in an expected range. Just a few teams do this real time during competition. A simple clamp on ammeter that clamps around one of the speed controller input wires is sufficient to check the current. An electrician usually has one of these devices in his/her toolkit. If you are interested in real time current sense search Stangsense on this site or on www.wildstang.org.

[Carl Owenby]

Most clamp-on ammeters that electricians use work only on AC circuits. Clamp-on that work on DC are much more expensive.

The most direct method is to use a current shunt that consists of a high wattage resistor (low resistance value) placed in series with the motor. Voltage measured across the resistor is then used to calculate the current.

[Al Skierkiewicz]

Since the motor drive is a pulsed system until you are at full output, a clamp on meter will give you a good indication of whether something is wrong in the drive train. Clamp on to one of the power supply wires feeding a victor and start to drive with the wheels off the ground at half throttle. If all looks fine and no breakers are tripping move on to the next step.
Put the robot on the floor, and have the driver slowly move forward and back while you walk with the meter. You should see higher readings than with the robot off the floor, but not excessive. Try a few turns and watch the meter. If the readings double or triple (or higher)those of straight ahead driving you might run into problems. Check all conditions (shifting, stopping, reversing direction, etc.) then move on to another motor. When you are satisfied that all motors of the same type are acting the same, under the same conditions, then try (with the meter removed)to simulate a match and see if you pop any breakers. (erratic drive or clicking sounds from the breakers)