Author Topic: Controller Card Swap Out...  (Read 6390 times)

GD George

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Controller Card Swap Out...
« on: April 12, 2020, 04:30:49 PM »
Some time ago, the MOSFET controlling the bed on my printer stick open.  As I've been printing PLA, I didn't really need the bed, so I disconnected it and continued on my merry way. At some point, I ordered a couple of MOSFETs and another ramps board.  Fast forward to yesterday.  I'm working on a prototype touchscreen to replace the audio head in my car, and I want to print it in ABS.  So now I'm replacing the ramps card. I swapped out the card, plug by plug and have checked my wiring but there's weirdness...

Steppers on manual control from the LCD are intermittent. Sometimes they work and sometimes they don't.
Neither the bed nor the top will heat.
The LCD seems to be getting power from ramps. BUT... It's also getting power from the USB, if I connect it.

I'm getting power to the ramps card from the PS. (And my multimeter just crapped out.)

So tomorrow, I'm off to pick up a new multimeter. Any ideas what to check next? I can go back to the old card for a bit, but I am going to need the hotbed eventually.

Any suggestions greatfully accepted.

Best,
Jerry

ggallant571

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Re: Controller Card Swap Out...
« Reply #1 on: April 13, 2020, 07:22:06 AM »
Did you test the current limit on the stepper drivers?
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GD George

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Re: Controller Card Swap Out...
« Reply #2 on: April 13, 2020, 03:06:45 PM »
Thanks for getting back. That's the little pot on each driver, right?  I haven't touched them since I built the machine. How do I test them?

Jerry

ggallant571

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Re: Controller Card Swap Out...
« Reply #3 on: April 13, 2020, 03:36:26 PM »
You use a volt meter. Connect the negative  lead to Gnd and the other to the trim post case. For single 12V motors with A4988 drivers the voltage should be about 0.45V. Higher allows more current which will also increase the heat dissipated in the motor. If you have 2 motors you need about twice the current so set the voltage accordingly. www.pololu.com has some excellent tutorials.
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GD George

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Re: Controller Card Swap Out...
« Reply #4 on: April 19, 2020, 08:32:30 AM »
Thanks, George. I took it apart and put it back together again and the motors are turning now. I also replaced my multimeter, so I'll check the current limit later.  I need to wait for it to warm up a bit out in the garage to see if the tip and the bed are working as they toss mintemp errors right now.  Quick question: can I put 12v from the PS directly to the bed long enough to ensure that it goes on? If I'm still having issues, I'm going to re-flash the arduino and see if that helps.

Jerry


ggallant571

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Re: Controller Card Swap Out...
« Reply #5 on: April 19, 2020, 11:35:02 AM »
It should be safe to drive the hot end and heated bed with 12V. Mine are 24V and some of the newer are 120V AC.
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GD George

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Re: Controller Card Swap Out...
« Reply #6 on: April 19, 2020, 12:54:36 PM »
OK, I just ruled out the bed or the tip as issues. Both heat up when hooked to 12V. The thermistors are correctly connected and both read within a couple of degrees of the actual temperature...

This is either a bad card or something stupid...

GD George

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Re: Controller Card Swap Out...
« Reply #7 on: April 19, 2020, 01:02:24 PM »
Oops... Should have sent this one before the last...

OK, so...  No power out to the tip or the bed (d8 and d10) but the fan (d9) switches on when I run the preheat for either.  I have 12v from the PS into the 5A. Right now I have the other 12v into an external MOSFET and the signal for that into d8. The tip goes directly to d10 and the fan to d9. I reflashed the printer but no dice. 

(Which begs the question: do I still need power into the 11A, even with the external MOSFET.) Note that I tried this with the power and bed directly to the RAMPS and it's still acting the same way.

What about LEDs on the RAMPS board? I've got a single red, and an intemittant green.

GD George

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Re: Controller Card Swap Out...
« Reply #8 on: April 20, 2020, 05:25:43 AM »
To do:

*I'll check the polyfuses this afternoon.
* bypass the thermistors in Marlin and see if the machine heats up. If so, do one at a time. I think I have a spare or two.
*If all else fails, go back to the old board and see if the the issues persist.

« Last Edit: April 20, 2020, 10:46:50 AM by GD George »

GD George

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Re: Controller Card Swap Out...
« Reply #9 on: April 29, 2020, 05:41:21 PM »
I decided to wait on some ferules and a crimper before reassembling my printer. Also bit the bullet and ordered another card and an arduino. Today, I reassembled the thing.

  • the polyfuses are OK. I checked across both legs of each fuse to ground and got 14v.
  • the bed works now with the external MOSFET. I looked at the wiring diagram that I was using and realized that it didn't show 12v going into the ramps card on the bed side. So no way to tell the MOSFET on the board to open up and send voltage through to signal the external one to actuate. Ran 12v back from the external to RAMPS and the bed fired right up.
  • Still no joy on the tip. Just to make sure its not the thermistor, I'm going to bypass it in the software. If that doesn't work, I'll just chalk it up to a bad board and replace it with the new one.

Best,
Jerry
« Last Edit: April 29, 2020, 05:43:40 PM by GD George »

GD George

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Re: Controller Card Swap Out...
« Reply #10 on: April 30, 2020, 10:30:56 AM »
MOSFET on ramps is stuck partially open.  (How is that possible?) 

Anyway, I hooked up another external MOSFET and the control LED lit up as soon as I started the printer, and the tip ran away.  Swapped control circuits (to make sure the external MOSFET wasn't the problem) and it responded correctly when I turned on the bed.

OK, I've got another card and just need to swap out parts. The question is: should I just swap motor controllers, arduino, etc? Or should I just replace the while kit-n-kaboodle? I have the parts, but I know everything in the existing setup (except the one MOSFET works...

I guess I could also take a MOSFET off the original board and put it on the current one...

Jerry

ggallant571

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Re: Controller Card Swap Out...
« Reply #11 on: April 30, 2020, 04:46:32 PM »
PWM on the input. Perhaps a cap for filtering. Do you have a scope?
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GD George

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Re: Controller Card Swap Out...
« Reply #12 on: May 03, 2020, 09:52:16 AM »
No scope.  I may have a scanner for my car that works as a scope though. But that's a different project for another day.

Thanks!
Jerry

GD George

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Re: Controller Card Swap Out... Printing Again!
« Reply #13 on: May 09, 2020, 08:26:15 AM »
Printing again! I wound up replacing the RAMPs card. I think that the original and the other replacement card each have a bad MOSFET, one for the bed, and one for the hot end.  While I had it apart:
  • Added the external MOSFET boards that I had purchased some time ago.
  • Generally tightened bolts and screws.
  • Updated Marlin to the latest version that I could find for my printer.
  • Enabled the EEPROM.
  • PID tuned tip and bed.
  • Put some silicon lube on the moving parts.
  • Moved the Raspberry Pi to a more convenient location and added a cam.

« Last Edit: May 09, 2020, 03:25:28 PM by GD George »

ggallant571

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Re: Controller Card Swap Out...
« Reply #14 on: May 09, 2020, 09:29:34 AM »
Now that you have "free" time while waiting for the prints to complete perhaps you could do a quick write-up on how you got octot print to play nicely.
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