Need Help with Motor Controller 29

I have a project going where I will need to control a lot of motors remotely. It is not for a robot or competition. It will be a very large model of a tracked crawler crane built from LEGO parts.

A friend of mine pointed me in the direction of VEX and using the Motor Controller 29.

One of the challenges of this project is the high power requirements. I will need to control up to 7 - 8 amps per channel. LEGO makes control equipment for their motors, but their system cannot handle anything more than 1 - 1.5 amps per channel.

QUESTION 1: Can multiple Motor Controller 29 modules be connected to work off one channel? Here is a link to a diagram of the wiring. The situation where the multiple MC29’s are needed is in the crawler base.

QUESTION 2: Will I need to power the MC29’s differently? Ie will the standard plug-n-play wiring that comes with these parts not be sufficient? Please see Option 2 and 3 in this sketch:

Any help or advice will be greatly appreciated. Thank you!

I am not sure about question 2, but for question 1 your design should work. The only concern would be the current running through the controllers.

If I’m reading this correctly…

  1. Yes they can. Are these standard DC motors? Then I’d wire them like I do FTC.

  2. It also should be sufficient to keep standard wiring.

Are you running those 7-8 amps continuously? If so the MC 29 has a max current of 4A. Run 7-8 continuously and those things will fry.

Thanks 536C and OscarNVCC.

The motors will be from LEGO. They are the Power Functions medium motor. Each motor has a stall current of 0.85 A.

So, if each MC29 is connected to 3 of these motors, then it should see just under 3 A total at max load.

The max load won’t be endured for any length of time, but I anticipate the final model to be very heavy and the motors will be pushed pretty hard at times.

So you want to control the Lego PF motors with a Cortex?

The Lego motors are pretty simple and can be ran by just applying power to it. I don’t know if you would need a MC29 for other uses?

Actually, I was looking into other 3rd party RF stuff (transmitter + receiver) to plug the MC29’s into.

What I’m looking for is PWM control over the motors and operate the model by remote control. I need on/off control plus the ability to vary the speed.

The LEGO PF system does make this possible, however, it’s very limited in the amount of power it can deliver. For what I want to do, I need a system capable of handling more power.

Also, the LEGO PF system is IR, and I’ve had issues with making it work well in past models. I’d much rather have a system that works with RF.

Okay, I see what you’re trying to do.

Have you considered other motors than the Lego PF ones? If you have something that needs a lot of power, I’m not sure if they will be enough. From my experience, the control system and battery has enough power to run a few motors under load, and it’s usually the motors that don’t have enough power. You can tell this because when you remove the load, they run normally again.

If I’m correct, I’m gonna assume these Lego PF motors are I2C based and not like CR servos or DC motors which means a little bit of extra work would need to be done to use an MC29.

Does the NXT not provide enough power if they’re hooked up to the NXT?

My design has 9 LEGO PF med. motors powering each side of the crawler tracks. Each motor (within the crawlers) will power a roller that runs on the inside top of the track. This is a bit different than how real crawler treads are powered - usually it’s a big sprocket on the end that is powered.

Please see the diagram that I made:

I’d prefer to keep the project 100% LEGO, but the controls and power options offered by LEGO just aren’t going to do the job.

LEGO makes larger motors (like the XL), but those are so powerful that they’ll twist a plastic LEGO axle apart when stalled. My solution is to distribute the power needed across multiple smaller motors, each with its own gear reduction.

I’ve tested a prototype assembly and the concept works. But I only used a few motors and powered and controlled it with the LEGO PF system parts.

The final model will have many more motors and will need more power (going beyond the capability of the LEGO PF controls).

I’m not sure what type of motor the LEGO PF motors are. I think they were just simple DC motors put into a plastic housing with built-in gear reduction.

I don’t have any NXT stuff. I’ve never messed with it.