As requested, we have begun researching the motor specifications of the Vex servos and motors. We will have DETAILED experimental results for you in a month or two. (We are having it done by an expert.)

Until then, we have some basic "quick" specs for you. As we get more information, we will post it to this thread.

The Vex motor free speed is approximately 100 RPM at 7.5V. It should be noted that DC motor performance varies slightly from motor to motor (due to variances in manufacturing).

Our experiments also determined that there is NO discernible winding bias on these motors. (The motor runs at about the same speed in FWD and REV).

The Vex Motor Stall Torque is approximately 6.5 inch*lbs.

It should be noted that DC motor performance varies slightly from motor to motor (due to variances in manufacturing).

What is maximum/minimun rated operating voltage?
Deadband appears to be approximately 1.4ms to 1.6ms, its that correct?

The operating range of the Vex Controller is 5.5 – 9.0 Volts which will be applied to the Vex Motor. If the Vex Motor was not connected to a Vex Micro Controller, the Vex Motor has a range of 4.4 – 15 Volts. Motor life will be reduced operating outside the Vex Controller range.

The nominal dead band varies from 1.47ms – 1.55ms but over all temperature and voltage ranges could vary from 1.36ms – 1.68ms.

The Full Reverse to Full Forward High part of the PWM Signal will need to vary from about 1ms to 2ms.

Do the motor modules have something like a temperature sensor in them so that when they over heat do they stop working for a certain amount of time, if so how long?

Yes, there is an auto resetting circuit breaker that will stop the motor from working when the load becomes too high. You must remove power from the unit and let it cool down for a few minutes. The Motor should work again if no permanent damage was done.

My son and I built the Square Bot with careful attention to the instructions. Our problem is that, while the bot does move, one motor moves in a start and stop fashion, while the other moves in a continuous motion. Could we have accidentally caused this when we were trying to set up the controller?

You may have a servo installed instead of a motor. Check the silkscreen markings on the back of the unit and verify you are using Vex Motors and not Vex Servos.

I have built a robot which uses a lever to lift a specific weight. I am trying to figure out exactly how much force is being exerted to the lever to lift the load. I have done some programming and have the motor lifting the arm set to add one point to the setting each time I push a channel on the transmitter. The programming tells the motor to increase the setting from 127 to 128, print to screen that amount, and wait. The lever wont lift the load until it has the proper amount of force. Long story short (too late for that), what units are each of those settings? Is there a conversion?

The settings have not been correlated with a force and do not a have units associated with them. The values 0 – 255 are simply the smallest increments/steps that you can send to a motor. All steps may not be interpreted by the motor to give 256 different output variations.

Is it Bad to use a Motor to hold something?

Yes, it is Bad to use a Motor to hold something. If the Motor is told to go fast but can not move, the Motor is in a Stall state 100% of the time in which it is drawing maximum current and will overheat the Motor quickly causing a loss of power. If the Motor is told to go very slowly but can not move, the Motor is in a Stall state maybe 10% of the time in which it is drawing maximum current and will overheat the Motor at some point causing a loss of power. This happens to try to prevent the Motor from burning up under heavy load conditions. The Motor should regain the loss of power after it has fully cooled off.

It is my understanding that several of the PWM outputs of the Vex controller (1 - 4, I believe) are controlled by the user processor (as opposed to the master) and can as such be controlled through a timer interrupt at a higher rate that the ~54 Hz at which the main program loop operates. With that notion in mind, what is the maximum update rate of the motor controller within the Vex Motor Module?

The Vex Motor will require about 700us of low time on the control signal input before the next pulses rising edge. Therefore the total pulse time is about 1.7ms to 2.7ms yielding an input frequency rate of about 370 Hz to 588 Hz.