Did I just fry my tech zone extruder board?

Fried board? Well yes, sort of, I assume. One of the A3949 ICs is smoking. And smoking is bad for your health.

I was testing the extruder with my tech zone electronics, and everything worked well. The nichrome heated up nicely (although gave off a bit of smoke in the beginning), and the thermistor supplied temperature readings just fine. But the stepper motor was running the wrong way.

To fix it, I turned off the power supply, plugged out the USB cable and continued to switch one of the wire pairs on the Nema17 Lin Engineering 4218L stepper motor, (just like I had done when the other motors ran the wrong way). But when I turned on the power again, the A3949 IC started to smoke within a second and supply a few not so nice sounds.

My theory is 1) This was either because the electronics was still connected to the power supply which was still plugged in the wall socket and thus was still grounded. Or 2) Overheating because of faulty firmware or bad connection? (We'll come to that).

(It still smokes if it gets 12v, but the rest of the electronics is working fine when I disconnect the extruder board).

I have another tech zone set, and with good help on the IRC channel (thanks guys!), I uploaded the same firmware to the new board and hooked it up.

Everything powered up fine, but when I plugged in the USB cable, the motor started making strange noises and stuttering movements which continued even though I unplugged the USB cable. I turned it on and off a couple of times, but it still made the same noise. It seemed like it perhaps tried to run a DC motor instead of a stepper motor? So I uploaded the extruder firmware again, just to be sure. This time the motor made a little noise and then stopped. So I testet heating and temperature reading, but when I tried to extrude it started to make funny sounds again. I measured one of the A3949 ICs with a IR thermometer and it showed more than 100degrees celcius! So i naturally turned it off rather quickly.


What am I missing here? The first board ran the stepper motor fine, but the second doesn't? I see many of the same symptoms as in this thread.


One quick question about the burned board:
Is it probable that it's only the A3949 that's fried, and I can order a new one from digikey? (Thanks nophead).


The first bump in the RepRap adventure had to come some day.

-Nudel

The problem is that the current is only limited by the firmware PWM setting so it is very easy to put too much current through the drive chips.

The current can be set by M code, or by the pot on the board. Maybe the pot is set differently on the second board?

Much better to get a fourth stepper driver and connect it to the two I2C signals that come from the mother board, which are actually step and direction.

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[www.hydraraptor.blogspot.com]

Thank you for the clarification nophead! Sounds like a good plan to use a separate driver then.

So I'm now assuming I can simply hook up a stepper board from the "spare" electronics kit I have? If the pinout is like the picture below, it means SDA/Step goes to pin3, and SCL/Direction goes to pin 4, right?



Perhaps the fried extruder board can still be used if I de-solder the smoking a3949 (or just let it burn out completely)?

Yes I think those are the right connections. 50/50 chance anyway ;-)
Don't forget to tie the enable pin (5) low.

Best remove the broken chip and hope it hasn't feed 12V back into the Arduino and fried that as well. If you let it burn more it may damage the PCB as you can get a lot of current from a PC PSU and there are no fuses to protect it.

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[www.hydraraptor.blogspot.com]

> Yes I think those are the right connections. 50/50 chance anyway ;-)
Hehe, about time I start living up to my signature.

> Don't forget to tie the enable pin (5) low.
I'm sorry, but that I didn't understand. Do you mean connect it to ground?

> Best remove the broken chip...
Thank you again! I'll look into that at a later stage.

> ...and there are no fuses to protect it.
Would it be a good idea to supply a fuse to the 12v line? What kind of fuse would be sufficient?

Once more, I really appreciate the help!

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-Nudel
Blog with RepRap Comic

Nudel Wrote:
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>
> > Don't forget to tie the enable pin (5) low.
> I'm sorry, but that I didn't understand. Do you
> mean connect it to ground?

Yes ground.

> > ...and there are no fuses to protect it.
> Would it be a good idea to supply a fuse to the
> 12v line? What kind of fuse would be sufficient?

6.3A in the 12V feed to the machine should be plenty enough current to run it excluding a heated bed.

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[www.hydraraptor.blogspot.com]

So, I've finally been able to follow this up, but I can't get the new extruder stepper motor to run.
With great help from Kliment and araspitfire in the IRC channel, we've narrowed some things down, and I'll give a breakdown here.


My Mendel is controlled via Repsnapper, and I can jog all axis, heat barrel and read temperature.

The extruder stepper is exchanged with a known working one.

Wiring is triple checked, so SDA from the motherboard goes to pin 3 on the stepper, and SCL goes to pin 4. (Tried to switch the pins as well, just to be sure).

The enable pin is grounded similar to this (I used a 10pin connector): tech zone wiki.

When power is switched on, all the leds on the stepper light up. (But they never blink or turn off while testing).

The motor is connected correctly, I measure similar resistance on the coils (1.5ohms I believe it was) and it locks when power is on.

When I run the extruder from repsnapper, I measure 2.4v on SDA and 4.8v on SCL. When run in reverse, I measure 0v on SCL.

I measure between 0.8v and 1.1v on the motor coils on the other stepper boards, and have turned the pot between 0.8v and 1.1v on the new extruder stepper to no avail.

The motor is making a small humming noise when powered on, which increases when turning the potmeter.

I've tried to heat the barrel to 200deg C, and then extrude. The PLA starts to drip out, but the motor will still not move.

Just now we've tried to increase E_STEPS_PER_MM from 2.02 to 90, (Wades extruder).


That should be it so far. Thanks for reading my story. Perhaps this could become a troubleshooting sheet for the tech zone wiki article someday?

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-Nudel
Blog with RepRap Comic

It's alive!

With good help on IRC, I did the following:


- Upgraded to latest (stable) firmware on the motherboard.

- Made a new, fresh cable with a simpler connector to ensure good contact.

- Turned the pot on the stepper down a bit.

- Enabled "use incremental ecode (for seperate extruder conroller" in printer definition settings in RepSnapper.


Now it's working as expected, and I just have to rebuild and rewire my extruder.

I noticed one interesting sign to look for if you want to see if the stepper board gets a signal. First you power up your mendel. (All the lights on the extruder stepper should light up). Then you attach and detach your usb cable, the lights will change and turn on and off in the same "activity" pattern you see on the other steppers when in use. Someone else probably know why.

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-Nudel
Blog with RepRap Comic

Can any one post techzone motherboard switch connections. please.