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Getting a motor to run as fast as possible..?

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Botanic:
Hello everyone!

Me and three other people are going to construct a robot as a school project. The mission of the robot is to get from a point to four different points as fast as possible. The robot is going to have a sensor to detect the four different points. There's some other requirements for the robot also, which I will probably ask for help with later on.

What we have so far is only the chassis with two motors that we have to use for the robot. We have no documentation for the motors.
The motors are directly connected to the rear wheels.

How do I get the motors to run as fast as possible without overheating them with too much current? Any practical information is appreciated.

The only thing that's on the motors is this: "RA250077-50C01  DC 6V  S.Y. TAIWAN".
I have googled some for the specifications but can't find anything.

Please help.

Admin:
This should help:
http://www.societyofrobots.com/actuators_dcmotors.shtml

Your motor says 6V, which means your motors run most efficient (therefore minimum heat output vs torque/speed) at 6V. Depending on your load (heavy robot? fast acceleration?) you can probably get away with 7 or 8V without melting your motors. Higher voltage of course meaning higher torque and speed. You can also heat sink your motor too.

The documention, if there is any, wont tell you about over driving the motor.

This may or may not be useful for you to optimize your robot speed and acceleration:
http://www.societyofrobots.com/mechanics_dynamics.shtml

Botanic:
Thanks! I had already read the first article. I thought that the documentation would give me some information about how much current the motor can take before meltdown...

I guess that we just have to test with different current to see what it can take before going too hot. Then get the biggest wheels we can fit it with without slowing it down.
We did some tests, and noticed that the motors can take 9 Volts atleast for a minute or so.

I found the manufacturer of the motors after some more googling. The company is called "Shayang Ye Industrial". I emailed them and asked for some documentation, just for kicks. I am quite sure that no one else of the groups in my school has any documentation. So it would be nice to boast that we have.

Any tips on how to test how much current the motors can take?

Any tips on a cheap and effective dc/dc converter that converts 6V to 6-9V for the motors? We are going to have a PIC to control the motors.

Admin:
Well, what you can do is this:

attach a wheel to the motor
apply your desired voltage
with your hand slow the wheel down
measure current and temperature

You will then notice the current go up (use a multimeter to measure current). Try and keep the current steady, and let your motor heat up. Best if you measure temperature and wait until the temperature becomes stable. Apply more and more torque until the motor gets like 200F (I think?). Slowly increase torque so that the motor temperature reaches steady state (doesnt get higher).

The reason you want to do this slowly is so that heat has a chance to travel from the coils to the outer casing of your motor. If you do it fast, you have a problem of instananeous melting, meaning that you have a high concentration of heat in a tiny area, causing melting in just that tiny area before the heat has a time to dissapate.

Once you feel that the motor shouldnt get any hotter, record the current being used. Thats your maximum current - meaning not even a current spike should go above that value.

In the end, it really all depends on the melting characteristics and heat dissapation of the components in the motor you have.

Afroman:
"Any tips on a cheap and effective dc/dc converter that converts 6V to 6-9V for the motors? "
Unless this is a motor that draws under an amp, it is almost certainly not worth the time/money involved in stepping up from 6 to 9. If you really want the higher voltage, a 7.2V NiCd pack sounds ideal for your situation.

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