Is it toast? <==Solved

My extruder stepper made a high pitch whine whenever it was idle. I was testing my current settings and filament spacing tonight and I noticed that the two IC's next to the stepper terminal block were extremely hot, so I let them cool down while I worked on adjusting my endstops for the axis. When I came back to the extruder controller the stepper wouldn't turn. The four LED's cycle but I have no movement. Did I toast this board? If so, what did I do wrong?

Edited 1 time(s). Last edit at 05/05/2010 09:21PM by J-Dubs.

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-J

True wisdom lies in knowing that you know nothing

sounds like they had too much current flowing.. one of the problems with driving a stepper from the extruder board is that there's no real current control, only open-loop PWM.

you'd be better off removing the chips and wiring a proper current controlled stepper driver in their place, then updating the extruder firmware to send appropriate signals.

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Wooden Mendel
Teacup Firmware

That's interesting. I assumed that it would have the same architecture of the stepper motor drivers. Can I just take the step and direction lines from the motherboard and connect them to a real stepper driver that accepts step and direction pulses?

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-J

True wisdom lies in knowing that you know nothing

I started up the electronics again tonight to start debugging and now I can't communicate with the motherboard. Things have gone from bad to worse.

When I open the reprap host software it says:

comms: G-code: T0 dequeued and sent [0.000s/-1272420286281ms]

and it stops there.
It was working before this whole fiasco but I double checked the baud rates and all of the wires anyway; but still I am unable to communicate with the motherboard.

Any help is greatly appreciated.

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-J

True wisdom lies in knowing that you know nothing

J-Dubs Wrote:
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> That's interesting. I assumed that it would have
> the same architecture of the stepper motor
> drivers. Can I just take the step and direction
> lines from the motherboard and connect them to a
> real stepper driver that accepts step and
> direction pulses?

should work fine, try it and see what happens

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Wooden Mendel
Teacup Firmware

I have cooled off now for a week so I didn't just pitch the whole thing in the garbage being that I am so so so close to a working machine (it is complete and was homing all 3 axis correctly before this happened).

I have called in my brother-in-law who works with embeded systems all day long to take a look at what is going on.

1st step will be to test my TTL device.

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-J

True wisdom lies in knowing that you know nothing

This is now solved - I had ground loop issues and noise issues. Re-wired the whole thing and the electronics are solid.

Edited 1 time(s). Last edit at 05/05/2010 09:21PM by J-Dubs.

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-J

True wisdom lies in knowing that you know nothing

@ J-Dubs ()
I have the same problem.. what did solve you're problem..
A ground loop .. how to detect that one ?!?!

looking for a solution..

Seems to me the extruder board locks up as soon as it needs to turn the stepper..
at least it looks like it.. it starts stuttering the motor but all very loosly.. I can hold it by hand and prevent from turning by holding the shaft...
But I feel pulses..

OK, I thought it was a ground loop problem so I re-wired everything. While I was re-wiring things I would troubleshoot each connection. I was trying to power my limit switches from the 5 volt output of the power supply. For some reason the motherboard didn't like that too much because it would shut down ttl communications when I did that. The extruder board was the same way, I had to power it from the motherboard to get it to work for me. Now all of my limit switches and the extruder board are wired according to the original design and that seems to keep it happy.


That being said, I was working with my extruder last night because it lacked torque, it pulsed but wouldn't feed the filament. I think that the current choppers are limiting the current to the stepper. I looked at the extruder firmware and the default PWM for the extruder stepper is set to 140 (I think that this is 14% see: [forums.reprap.org]). I read that if you send the machine a M108 and a value that this will set the current for the extruder stepper. If you are using the Reprap software go in to the preferences menu and click on the Extruder0 tab. There is a setting called Extruder0_ExtrusionPWM (see: [reprap.org]), this is the amount of current that the host software tells the Extruder board to give to the stepper, ie. 0.6 is 60% current (I think that this is supposed to send a M113 if set to zero). When it writes the G code for the part program it puts an M108 in the beginning of the program with the value from the preferences page. M108 is modal. The M113 command tells the extruder board to use the onboard potentiometer to control the current (check out [reprap.org]). M113 is modal. That is where I fell asleep last night, so I haven't had the opportunity to verify if any of this will work.

I hope that some of this is useful to you. Good Luck!

Edited 3 time(s). Last edit at 05/11/2010 02:29PM by J-Dubs.

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-J

True wisdom lies in knowing that you know nothing

And... Any luck on resolving this issue, BECAUSE I have exactly the same problem.
I can hold the extruder stepper motor shaft with one finger and prevent it from turning, i.e. no torque whatsoever. For the X, Y and Z-axis this is not the case at all - but then they are using proper stepper controller chips.

If you have a solution I would love to know it!

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

oops
I was going recommend something you already seen......

what i'm planning is to use a stepper board to drive the extruder...

I already tested it... just waiting for the 4th stepper boadr to arrive...

plus I/m upgrading to a wades extruder...

Edited 3 time(s). Last edit at 05/21/2010 01:47PM by Mdbaughman2.

I already have a Wade extruder but with zero torque even Adrian's version wouldn't help! I was thinking of purchasing the polulu stepper boards to drive the extruder motor, but as far as I know the majority of people with Mendel Gen 3 electronics are using the extruder controller to drive a stepper motor. Are they all using 2 - 5 volt stepper motors?

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Sorry that it took me a while to get back to you. I have been chasing my heater around trying to tweek it so it does what I want. FYI, check out the extruder controller page, it says to use output "B" for the heater because it is the only output of the three that is PWM. My firmware was using an analog write to pin 12 which is not PWM.

Setting my default PWM to 700 and my Extruder0_ExtrusionPWM to 80 solved my problem, but I haven't fine tuned my values to match my stepper yet. What value is set in your firmware for defaultPWM? What value is set in Extruder0_ExtrusionPWM in your software?

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-J

True wisdom lies in knowing that you know nothing