SparkFun Forums

[AXN-RXN]

Hi All,

Hey, I'm on a project right now that uses a bunch of BED to power Nema 17 stepper motors. We've been having trouble with these board bursting into flame. At first, we found that that current pots were shipped pegged to full on. On power up, they would fry with an exciting orange flame. We were able to solve that by turning the pots all the way counter clockwise and adjusting them from there. It's still kinda wierd, because we running within the spec'd voltage limits and boards will burst into flame even without any motor attached. We're running the power supply to the +M and GND pins for the stepper, 4-wire stepper goes to the stepper pins, the other pins used are step and direction. We also have the M1 and M2 pins jumped to the second GND pin on the board to get 1.2 stepping.

Here are the motors:
http://www.automationtechnologiesinc.co ... 3d-printer

But, we're still frying boards left and right. Some boards that we've had working perfectly for a while will suddenly just go up in flames. When they are working, the steppers run nice and smooth, boards are a little hot, but nothing crazy. We are not using heat sinks, but the flamming boards don't exhibit a thermal shutdown mode beforehand, either. I'm thinking that it may just be with our power supply. We're using a big one, since we're trying to drive 20 BEDs. We have a 24v/25A power supply. But, we're starting with the current trip pot all the way down and just slightly adjusting it up until the stepper moves happily. Lots of the boards are flaming up even without any motors connected or drawing any current.

Is the power supply just too beefy? I'm of the understanding that even if the power supply could be capable of 1000 amps, it will only dish out what the motor requires. Also, I beleive that you can run steppers safely at 24V, as long as the current limit is set low on the pot. We're not getting any hot motors. So, I'm unsure if the power supply is the issue.

Anyone have any ideas what could be up? Anyone ever have the same issue? Thanks,
--> Karl

[waltr]

Which part on the board is going up in flames?

[dlotton]

Am I missing something? The link says the motor's rated voltage is 2.8V... and your supply is 24V?

[AXN-RXN]

The main chip seems to be frying.

Yes. The motors are 2.8v. You can typically run steppers at much higher voltages, as long as you keep the current pot dialed back. I'm running Nema 17 motors at 18v on another project (with the same BEDs) with no problem. Maybe I'm wrong, but if the motors were too small for the voltage I'nm supplying, I'd think I'd be ruining motors. But, all the motors run cool. If I have the pots turned up too high, the chip on the BED will cycle on/off as it hits the thermal limit, as it should. In this case I can dial it back until it works. As I stated above, a number of there boards lit up even without a motor attached...

[Ross Robotics]

I have a Big Easy driver running a Nema 17 for over a month and haven't had a problem with it. Running at 24V. Either you have something wired wrong or your voltage/current supply is not putting out a clean form.

Another thing to note is you have placed the step pins in a LOW, LOW, HIGH (MS1, MS2, MS3) state. This configuration is not on this table at the bottom of the page. Try changing the step pins to a known state.

[dlotton]

The motors are 2.8v. You can typically run steppers at much higher voltages, as long as you keep the current pot dialed back...

Okay, admittedly I don't have a lot of experience with steppers.

Either you have something wired wrong or your voltage/current supply is not putting out a clean form...

I was having similar thoughts. Are you using a bench power supply or some sort of wall wart or brick power suppy? Sometimes wart/brick supplies have broad tolerances, especially at light loads, which would also explain the issue with no motor connected.

[AXN-RXN]

I have a Big Easy driver running a Nema 17 for over a month and haven't had a problem with it. Running at 24V. Either you have something wired wrong or your voltage/current supply is not putting out a clean form.

Another thing to note is you have placed the step pins in a LOW, LOW, HIGH (MS1, MS2, MS3) state. This configuration is not on this table at the bottom of the page. Try changing the step pins to a known state.

Right. My mistake. I have the pins hooked up as High, Low, Low (M1, M2, M3) for the halfd step as in the chart. Sorry for the typo.

We're gonna just switch out to a more industrial driver. The automotion technologies KL-4030 have worked great in the past, but they are just big and bulky and take up a lot of space for 20 of them. They seem to have better protections and can cary much more amperage, so at least they won't start us on fire. Too bad, because these BEDs really fit the bill size-wise.

I agree on the power supply comments though. Thats all that I can come up with as the culprit. We're using a Mean Well Model Se-600-24 which has been a pretty good unit in past projects. If we cantinue to have problems I'll put a scope on the power and see if we can't fix anything with caps & diodes. The inrteresting thing is that the BEDs seem to fry right on start up. Haven't really fried one after its been running. So, there may be some sort of voltage/current spike right after power up....

Thanks for all the help!
--> Karl

[Mee_n_Mac]

The designer of the BED is fairly active on these forums. Have you tried e-mailing him re: your troubles ? My guess is he'd like to see one of two of the fried devices to figure it out.

http://www.schmalzhaus.com/

[fll-freak]

I have destroyed a few of these boards when the motor was turned and the power was off to the board. The BED is not protected for back EMF and will get fried. If you continue to back drive the motor, I could possibly see a possibility of flames.

Edit: I stand corrected. As per the post that follows, the chip does have some back EMF protection but not enough for larger motors.

[EmbeddedMan]

The Big Easy Driver does actually have protection diodes built into the A4988 driver chips. However, they will not tolerate a larger stepper motor being driven with the power off. For that, you'll need some hefty diodes of your own added to each of the four motor lines.

If you plugged an Big Easy Driver into a power supply without a motor attached and it burst into flames, I can only suspect that there's something wonky with your power supply. All boards are thoroughly tested by Spark Fun before leaving the factory.

That being said, it's not impossible that connecting or disconnecting a motor while the BED is powered could damage it. You need to be careful to only change the motor, or allow any disconnect of the motor wires, while power is off. The A4988 BED is more robust than the A4983 version that SparkFun was welling for quite some time. And both are more robust than the Easy Driver.

The BED is not really meant to be used in an industrial type setting - if you want really solid performance and lots of protections, get an industrial stepper motor driver. It will be worth the cost because you won't ever have to replace it.

*Brian