Frying A4988s boards

Other Hardware Product Design
1

Hi folks,

Haven't been here in a while but now that I'm retired I've gotten into Stop Frame animation and have broken down an old CNC machine I built with some students and am trying to retask it as a camera mount (EOS Rebel T7 or a Canon M200) so I can move it across a Lego set and also pan and tilt the camera. I have been using the circuit below with the attached code. It is setup EXACTLY as shown with the exception that I am running 2 power supplies, a 12 Volt and a 5 Volt. The 12 Volt is hooked up as shown and the 5 Volt is connected to the 5 Volt buss. I am also using a 100K pot. I tried using the 3 A4988 boards from the GRBL board and none of them worked. So I purchased a 4 pack of POLULO A4988 and have fried 3 of them, one to the point that the chip and sink fell right off the board because it got too hot.
What I have discovered is that the entire circuit can be connected but once I connect the +5V to the A4988 board, the board will fry. I have tried hooking up the 12Volt and %Volt power in separate ways (hook up the 12V connects first, hook up the direction/step pins first, hookup the motor connections first/last, etc.) but once the 5 V connection to the board is made the chip fries.
I have gone thru basically 5 A4988 boards. I don't want to continue making circuit board toast. Anyone have a clue what might be wrong? The power supplies are putting out the correct voltages, I have checked out the circuit a dozen times just to make sure it's wired right. I am baffled by this situation and have ordered a prebuilt interface to see if maybe it's the motors but we really didn't run the CNC but 6 or 7 times and never had a problem. Any ideas on what I'm missing here?

MANY THANKS!!

Joe B

image
image1484×984 183 KB 

#include <Stepper.h> 

#define STEPS 200
Stepper stepper(STEPS, 2, 3); // Pin 2 = DIRECTION & Pin 3 = STEP Pin of Driver

#define motorInterfaceType 1
int Pval = 0;
int potVal = 0;
void setup() {
  // Set the maximum speed in steps per second:
  stepper.setSpeed(1000);
}

void loop() {
  potVal = map(analogRead(A0),0,1024,0,500);
  if (potVal>Pval)
    stepper.step(10);
  if (potVal<Pval)
      stepper.step(-10);
  Pval = potVal;
}
2

HI,
Can you please post some images of your project?
So we can see your component layout.

Have you got the gnd of both power supplies connected together.

Can we please have a circuit diagram?
An image of a hand drawn schematic will be fine, include ALL power supplies, component names and pin labels.

A 10K pot would be better, as to high a value will be susceptible to noise.
A 0.1uF cap from A0 to gnd will also help.

Thanks.. Tom.. :smiley: :+1: :coffee: :australia:

3

As Shakespeare said "Ah there's the rub".

If a board gets too hot there is too much current. What have you set the chopping regulator current to? What ever it is it is probably too much. Also a 47uF capacitor is unlikely to do much for your smoothing try at least 1000 uF.

Also your narrative seems to imply you are making wiring cha ges when the circuit is powered up, a very bad move.

What we need is an EXACT picture of what you actually have.

The problem is unlikely to be software related.

1 Like
4

I can see several problems:

The 5V pin on the UNO is an output NOT an input.

Using a breadboard for high currents is a bad idea and many of the cheap ones have intermittent contact problems. At least solder all the connections to 1A, 1B, 2A, 2B, Vmot and GND (next to Vmot).

A 100uF electrolytic cap should be soldered directly to the Vmot and GND pins of the driver.

1 Like
5

Moving a motor wire while the circuit is powered up will instantly destroy a motor driver. Solder connections to motors and motor power, or use screw terminals if provided.

You should be aware that breadboards are for temporary experiments with low power logic circuits and cannot handle motor currents. The tracks burn, which also leads to damaged motor drivers.

6

ALL,
Thanks for the tips!

Hey Tom,

First, no I didn't have the grounds tied together. Will do that.
Second will switch from the 100K to 10K pot
And will add the 0.1uF cap.

Hey Grumpy Mike,

I am using a couple of power supplies that I was using for my LED lighting. One is a 12V 5A and the second is a 5V 5A. And NO, I don't hot wire. I learned my lessons LONG ago at RCA/GE Solid State. I have a switch on the AC line going to the power supplies that makes it very easy to toggle the power off. I don't run the Arduino off the computer. Typically I will turn off the AC power, connect to the iMac, upload the program, disconnect the Arduino from the iMac, then power back up.

Hey Jim-p

While I have been soldering for 40 years the last 5 or so have become increasingly difficult because I have developed essential tremor and while I can solder some larger items, small stuff is a disaster. What I do now is use jumpers. There is a connector off the NEMA 17 that I plug directly to the A4988 board. Anything else (2,3) go directly to the Arduino via jumpers. The A4988 board and the Arduino connect to the power via jumpers. Unfortunately I use a breadboard to run the busses and nothing else. Also never knew that the 5V pin on the Arduino was an output. Been using it for decades as power in. Guess I have to find a plug for the board that I can wire up to one of my supplies. Thanks you for pointing that out!

Eventually I will be sticking a Conceptinetics DMX shield on top of the Arduino so I can control the steppers via DMX. I have an Enttec DMX USB Pro hooked up to my computer.
The reason for all this is that I've written a musical and am using Lego mini figures to do the acting/singing. I am using Dragonframe 5 to do all the Stop Motion manipulation. Dragonframe has a DMX interface so I can accurately and repeatably get the camera (Canon EOS Rebel T7) to the dolly point and pan and tilt settings. I also can control the "stage" lighting via DMX.

So why am I telling you all this? Because at this point my office is a wreck because I'm putting the lighting in place. And all the electronics have been neatly stored until I'm ready to work on it again.
Once again, I thank all of you for the very valuable information you have given me and I promise I will send a picture of all of the setup as soon as I put it back together.

Very best regards to all of you and stay safe!
Joe B

7

Hi folks,

I finally just ordered a couple Microstep Driver interfaces so my steppers are performing as I need them to. Of course now I have to get the DMX interface working. Wish I had documented everything when I went thru the DMX stuff so now I have to go out and find some people familiar with the old Conceptinetics boards.
Once again I thank you all for your efforts in trying to get the discrete stepper boards working.

Best regards,

Joe B

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