Dagu 4 Channel Motor Controller - Blue Smoke Won't Go Back In

Help & Support Robots & Kits
1

My current robot project consists of the following components: Dagu 4WD Rover 5, Arduino Mega with proto-shield and mini breadboard, Dagu 4-Channel Motor Controller (product code RB-Dag-55), Dagu IR Compound Eye with Pan & Tilt Head, wired Wii Nunchuk, and a 7.2V/2000mAh NiMH battery pack. I was proudly demonstrating my robot to my co-worker when the robot backed over the nunchuk cable, pulled my mini breadboard partly off the proto-shield, and yanked out the +5V connecting the Arduino to the breadboard to the motor controller logic.

This caused magic blue smoke (with a little flame) to escape from one of the SP8M3 ICs on the 4 -channel motor controller (U8 for CH3 motor). I wasn’t quick enough to capture all the blue smoke, and even if I could I’m not sure I could have put it back into the IC. Needless to say, U8 looks a little charred and CH3 motor is no longer working. The other motors (CH1, CH2, CH4) seem to be working fine though.

My question is: would it be worthwhile to desolder and replace the damaged IC? Where can I find a replacement SP8M3, without having to purchase 2500 of them? Is it likely that something other than the SP8M3 is also damaged? Or am I just better off purchasing a new controller?

I understand that the motor controller instruction manual states that the motor power should not be connected without first connecting the +5V for logic, and I had heard of others who lost their magic smoke because they did not follow this. I was very careful to not let this happen to me (up until the robot backed over the nunchuk cable) but it happened anyway by accident. It seems a little too easy for the controller to fail in this way.

In any case, I’d like to consider other (i.e., cheaper) options before I go out and order a replacement motor controller. Any suggestions?

03-03-2013 Update - Here’s a photo of my 4-channel motor controller board with the damaged IC:

IMG_0781.jpg
IMG_0781.jpg2048×1536 401 KB

As far as I can tell, only U8 is visibly damaged. I found that Newark has a small quantity of SP8M3 available for US$1.14 each. I’ll probably order a few of these just in case I mess up on replacing U8 or discover that one or more of the other SP8M3s are also damaged.

2

It’s been a while since I’ve lost the magic blue smoke from an IC, and was a little surprised that it happened just by disconnecting the +5V. But I understand why it happened and will prevent it from happening again.

At the moment I’m leaning towards replacing versus repairing this controller with the same make and model, since I need the ability to control 4 motors with encoders. My controller also has a current leakage issue with CH4 that I was never able to resolve (Dagu 4 Channel Motor Controller - Current Sensing), and a new one will hopefully not have the same issue.

I may later decide to repair the controller anyway. Thanks for the advice.

3

It is sad to see the magic blue smoke go, it happened to us more that we would like to admit it.

In your case, the Dagu motor controller is fairly low cost considering it can control four motors and has encoder inputs. However, if you are not using all four motors or do not need encoders, then we might be able to find you a replacement solution.

It is hard to tell if you will be able to repair the controller by replacing the chip since some other components (capacitors, resistors perhaps some traces) might be also damaged and it is indeed difficult to find that chip sold as single units.