Motor Controller

**We are happy to announce that the Vex Motor Controller, which can be found on this page, is now available for purchase.

This Motor Controller will allow you to use VEXplorer Motors with the Vex System. It takes the PWM control signal from the Vex Controller and coverts that to a varying DC voltage which the VEXplorer Motor requires.**

Awesome!!! Can’t what to order that so I can use my vex blue motors with my vex red! :smiley:

My PWM->DC adapters arrived this afternoon, and I’ve had a few minutes to play with them. Here is an initial review:

The first thing I noticed is that there is no instructions included with the adapter, nor any documentation I could find on the VexLabs site. Not a big deal, but I was curious if it supported VEXplorer accessories (light, camera) or just the motor. More on this later.

The product itself is basically a 35cm extender cable with a small bulge in the middle. This bulge is a heat-shrink covered circuit board with a 3-wire cable coming out one side and a 2-wire cable coming out the other. The bulge is about 1cm thick by 4cm long by about 2cm wide. The whole thing only weighs 5g. There is no provision for mounting it, but zip-ties will be more than sufficient.

It seems to work exactly as advertised and is easily able to drive the VEXplorer motor from a PWM port on the Vex Microcontroller. The motor was dead stopped at 127, and the speed smoothly increased as the value ramped up. Ramping values below 127 smoothly increased the speed in the reverse direction.

At full speed, the power of the motor seems very good. The adapter did not get particularly hot after a minute or so of running at full speed.

One nice thing about DC motors is that you can reverse the direction just by flipping the polarity of the connection. So, if you plug the VEXplorer motor in backwards, you get reversed rotation without having to change the software or the transmitter.

As for the VEXplorer accessories, I tried plugging my VEXplorer LED lamp into the adapter. It worked exactly as I expected it to: The lamp was dark at 127, and increased to full brightness as I ramped to 255. Values below 127 yielded no light. Plugging the LED module in the other way around made the light full-brightness at 0 and, dimming down to off at 127 and above. One important caveat is that at intermediate brightness levels, there was a noticeable flicker. Not so bad that it wouldn’t be useable, but probably best to just run the light at full or full off.

I’ll run some Y-adapter experiments after dinner to see how it handles two VEXplorer motors in parallel. Also, I’ll try out some non-Vex parts like small bulbs, relays, and motors to see what happens. From my experiments so far, I think it will handle this kind of add-on just fine.


  • Dean

I was thinking about ordering one of the motor controllers, but I wanted to ask someone who had one a few questions first.

Honestly, how does it look - did they really do a good job on it?
What about the wires and connectors - do they match the regular VEX and VEXplorer cables?

If you could let me know so more details that would be great. It is really hard to tell anything from the little picture that is on the website. If there is any way that you could post a picture of it, that would be even better.

Thanks for all of the excellent information and testing!

Not FTC legal I am guessing. (VEXplorer moter)

It is a nice product in my opinion.

The input cable is the familiar White/Red/Black ribbon with the green Vex-custom servo connector - looks like identical to any Vex accessory. The output cable is a slightly thinner Yellow/Black wire with a standard 2-pin socket (no polarizing tab or outer shell). Basically, the wires and connectors are on-par with the Vex Labs extensions cables.

The electronics is just a small board ins heat-shrink tubing. It isn’t the most beautiful creation, but I don’t think the extra cost of a molded plastic housing would have been worth it.

Wish granted:

My pleasure!

  • Dean

Well, Dean took pictures and answered while I was busy doing the same. He beat me to it, and with better pictures than mine.

I will point out that this is the identical motor controller circuit board that is used in the Vex motors.

For those that want to push the envelope, note the component near the black wire (of the black and yellow pair) it has a marking that looks like 7XL. I am pretty sure that is a resettable PTC fuse to protect the motor windings. The specs on the Vex website say the controller is thermal limited to 1 Amp, so this is probably a 1Amp resettable fuse. If you want to drive a bit larger motor, you may want to bypass that component. The Infineon motor controller chip (the large one on the back) has its own internal thermal limit and is rated to handle 9 Amps (peak, not continuous)

That explains the superfluous cable grommet around the PWM cable. This is just a standard part with an output cable added and some heat shrink around it. Great reuse of a well known design.

That was my thought as well.

I haven’t looked at specs on that chip (yet), but I think I would try to heat sink it for any load significantly higher than 1A. Another upgrade that may be worth trying is to add a battery input, so that you can run the DC motors off a separate battery from the rest of the Vex system.

I did test a bunch of random devices, and it always behaved as I expected it to.

Two VEXplorer motors (in parallel): Worked just fine. It sounded like the RPMs fell off just a tad when I attached the 2nd motor, but hard to tell. Seems like this would work well to drive a 4-wheel drive chassis using 4 VEXplorer motors, plus 2 of these adapters, plus two Y-cables.

VEXplorer LED Modules: Worked just fine. Since they are LEDs, they only work with one polarity. Attaching two modules such that one is reverse-polarity allowed me to alternately activate one or the other module. As previously stated, the LEDs flickered at the intermediate brightness levels, but this is to be expected from a switching motor controller.

Incandescent Light Bulb: Worked just fine. Full bright at 0, dimming down to dark at 127, returning to full-bright by 255.

12VDC relay: Worked just fine. Relay closed at just over 200. This board can alternately drive two relays if you put a rectifier in series with each relay coil. That would allow the two buttons on channel 5 (or 6) to each control a separate relay using a single PWM->DC adapter.

Random low-voltage DC motors: Worked just fine. Some higher-torque gear motors I picked up from Jameco ran like a dream. Also ran a DC fan - it was kind of neat to control the fan (both speed and direction) from the Vex.

From looking at the output signal on the O’scope, the drive is a 2KHz duty-cycle output. It was fairly stable, and had nearly no dead-band. Basically 0-30 were full negative, 128-130 were dead off, and 222-255 were full positive. If you are running something like the camera that would not take kindly to being pulsed every 500usec, you should stick to 0/127/255 values.


  • Dean

I would say that you are correct.

this was a simple yet good product to release
i dont know if any realize it yet but those are the insides of a vex red motor
they took off ten dollars because there is no motor or gears or the case which is a great deal
so instead of having to buy a vex red motor and re solder another motor and waste 10 dollars and parts and time you can get this
overall:10 i like it!!

do they work with the solenoids for the pneumatics

Yes they will work, but this is NOT recommended. You may reduce the reliability or longevity of the Solenoid or the Motor Controller.