Looking for a *safe* dual-channel 60+ amp brushed DC motor controller

Help & Support Robot Parts
1

I’ve got a large 6-wheeled bot (about 6’ wide by 7’ long and a few hundred pounds when it has everything on it) with a pair of 800-watt 36 volt brushed DC motors. I’ve been using an MCP266 motor controller but it’s been a little problematic from the start.

During initial testing I found that it’d frequently lock up if a laptop was plugged in via USB. This caused the bot to suffer a crash that bent up the frame. That was about two years ago, and I’ve avoided using it with the Ion Studio software.

Last week I was doing some testing on new batteries and it wasn’t responding to the remote control, so I shut down the remote control and hooked up the laptop to check the settings - but NOT to run the motors. The motor controller spontaneously turned on the motors when I plugged it in, knocked me over, took off without the laptop (which got yanked out and tumbled to the ground) and then it smashed me into a bunch of equipment. Since then, with the bot up on dollies, I’ve had it spontaneously start the motors and stop accepting commands without even plugging in the laptop or turning on the remote.

Fortunately I’m just bruised and scraped up, no broken bones, and I’ll be fine in another week or two. But obviously I’ve lost whatever confidence I might have still had in this controller. It’s clear that there’s no hardware watchdog timer to put it into a safe mode when the software locks up. Also, the emergency stop option has never been usable because it trips every 10 or 20 seconds on its own, even with a 1k ohm pull-up on the input. I was only able to shut it down when it had me pinned because I was already reaching for the main breaker.

The manufacturer hasn’t responded, and after the trouble I’ve had with deceleration limits not being implemented, current limiting being inconsistent, and a bunch of other software issues, I’m not too inclined to pursue any solution from Ion Motion / BasicMicro.

I see a few different options here. Can someone tell me if any of them are known to be a little more safety-conscious in their design? At this scale a bot isn’t a toy, it’s a dangerous piece of equipment and I need to be able to trust the electronics.

Thanks,

Scott

2

Hello @madsci77!

Your project sounds awesome!

I’ve checked RobotShop and maybe you could try one of these:

Anyway, maybe you should install deadman switch somehow. I know all teaching pendants that I’ve used in the industry have them. Something like this:

Also, we would like to see your project in Robots section.

Stay safe!

3

That’s the one that was at the top of my list. I’ve emailed RoboteQ to ask about their safety features in more detail, and to see if they think it’d be a good fit for this project. One of the other problems I’ve had is that after they did implement acceleration limits in a firmware update for the MCP266, I wasn’t able to use it because there seems to be something screwy in the current limiting - the bot uses skid steering and with acceleration limits on it’d never get enough torque to turn. I’d expect it to make the steering a little mushy, but not to make it unusable.

After the first crash, when I found out it could lock up when a laptop was plugged in, I did all of my testing with a lanyard tied around the main fuse. If it got away from me, it’d just pull the fuse out. A remote dead man switch would have to have a reliable, independent radio and something independent of the motor control to disconnect power. It’d also complicate driving, since using the remote really needs both hands, at least as it’s set up now. I’d probably need to allocate another channel on the remote for a disconnect relay - or maybe just put an R/C servo on the main circuit breaker’s lever!

It’s more than a year out of date now and the bot has had thousands more LEDs and a mist spraying system added, but here’s my write up from the original build. Maybe after this year’s mods are done I’ll post something in the robots section here.

Thanks,

Scott