Dual VNH5019 & Scooter parts - Motor Fault

Support Motor controllers/drivers and motors
1

Premise:
Anyone see Wreck-it Ralph? I have been working on Sergeant Calhoun’s hoverboard from the movie.
Inspired by a probably-joking comment from my BF that it should be motorized, it’s now motorized. I don’t have a great pic of the setup, but in this image, you can see the two scooter wheels set up in the middle-back. The casters in the front keep me from falling over entirely and there is also one behind on the tail.

Electronics Setup:
Arduino Uno powered by a 9v. Controls are via a wii nunchuck hooked into ports A0, A1, ground, power. Dual VNH5019 shield attached to 2 Razor E200 motors (200 Watt Motor, 24 Volt, 2750 RPM, 11 Amps) and a standard 24v scooter setup (2x 12v 10AH lead acid batteries in series). With the board, wheels, motors and batteries, i’m guessing weight is around 40 lb. Motor/wheel setup inspired by a guy who made a self balancing skateboard using the two motors, wheels, batteries and a sabertooth controller. i went with pololu for the reputation (a friend of mine said you guys were an excellent company, and i’m, admittedly, an electronics noob, but an eager and fast learner) and the fact i found a controller that works for my purposes half the price of the sabertooth.

Problem:
I am getting motor faults. I managed to test drive my hoverboard around without me on it, and it worked fine (well, relatively. i have some steering tweaks to make as it’s not as responsive as i’d like). When I myself, tried to ride on it though (bringing weight to 200 or so) it moves, then seems to stop after 10 feet. I hooked up my laptop and set it on the board and it’s giving me motor faults (mostly 1, but sometimes 2). I’ve attached my arduino code.

A friend of mine, who helped me setup the wiring and such on it thinks maybe that i’m not giving the motors enough amps (the batteries power both) and so when i get on the board myself, it panics. I’m able to reset everything (don’t have a specific system for resets, yet) to get the motors to go again when i flip it over, but it’s a consistently sporadic and inconsistent problem. heh.

Would adding a second set of batteries fix the issue? If so, would I have to upgrade my controller?
NunchuckMotor.ino (5.84 KB)

2

Hi.

Cool project!

It is very likely that your motors are drawing more current than the VNH5019 can handle and the driver is overheating. When you put a total load of 200lb on your platform, the current is probably much higher than 11 A per motor (can you use the current sense feedback from the driver to see how high the current is getting?).

Generally speaking, that driver is probably not capable of putting out the kind of power you need for a motorized scooter; you might consider using a pair of our Pololu Simple High-Power Motor Controllers 24v23 instead.

Although I do not think this has anything to do with your problem, you are probably also exceeding the maximum recommended voltage of the VNH5019 shield, which has over-voltage protection that can trip at voltages as low as 24V. Your batteries will be much higher than this when fully charged.

-Derrill

3

Ahh, that makes sense. I guess I perhaps didn’t read all the fine print on the “low as 24v trip” – I liked the VNH5019 particularly because it was an uno shield, and thought the 24v would be sufficient. Perhaps when it cruises around empty, the motors draw little enough energy, but at 200, they spike and overheat the controller, causing the motor fault? the main difference between my setup and the skateboard tutorial is the motor controller.

Only thing with overheating controller is the controller itself never felt hot - only ever slightly warm. the manual said that it would get hot enough to burn before they overheat. I don’t have the code to currently output current, but that’s an easy fix - i will test it as soon as i can this week with current output and report back. Per the sample code for the driver, I can output current in milliamps.

4

I’m not sure if your comment is somewhat tongue-in-cheek, but please note that it is not our intention make it seem like this driver will work with 24V batteries while hiding some kind of warning in “fine print”. We try to be very clear that this driver has a maximum operating voltage of 24V and is not appropriate for use with 24V batteries unless special precautions are taken to limit the peak voltage.

Although the chips can get hot enough to burn you before they overheat (they can easily operate continuously at temperatures over 100°C), they can also overheat in ways that do not generate much external heat. For example, a large current spike (e.g. 30A) will heat the chip internally to temperatures that trigger the over temperature cutoff in a few milliseconds; this heat dissipates quickly once the drivers shut down and does not raise the board temperature significantly.

Please let me know what you find out when you look at the motor currents.

-Derrill

5

nope, it’s entirely my fault that i missed that. it’s not really fine print - i think i had read the 24v top end and then didn’t pay enough attention to the warning below about 24v overages and didn’t really think about the fact that they can go over that level slightly myself.

6

Weeee… amperage crazy. Before the M2 fault, the milliamps peaked at 28016 for that motor. I had it turning, so the other motor was low. That’s probably what is tripping the faults - thus underpowered controller. :confused:

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Thanks for the update; that seems much more in line with what I would expect from big motors like that, and it certainly makes it clear why the VNH5019 drivers you have were overheating.

-Derrill

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Yay having to replace the most expensive part of my board! :stuck_out_tongue: Thanks for helping me troubleshoot, though. At least it’s a fixable problem.

When looking at motor controllers, I made the (incorrect) assumption that 11A motors would run, at the most, 11A, which is why I thought the 12A VNH5019 would suffice. Having never worked with DC motors before, I guess it’s an understandable noob mistake. Now to get and upgraded controller setup and come up with a new project for the VNH5019… hmm.

9

It is often difficult to determine what is meant by the manufacturer when a motor has a rating of 11A. There can be a lot of variation in what that means (e.g. peak efficiency current, free-run current, stall current, etc.).

I hope you get your project up and running; it looks cool!

-Derrill