Ramps 1.4 damaged by measuring with multimeter?!

hey guys.

I am on my second 3D printer - a prusa i3 which i am quite happy with.

since i have been experiencing some Y-axis shift in longer prints lately i wanted to measure for a little bit higher V-Ref on the trim poti.

I therefore set the positive side of my multimeter on top of the poti and the negative gauge on to the (supposedly) gnd pin.

Accidentally i mixed up the potis on my 4988 Drivers from Gadget 3D - which have two trim potis on each driver, one for Vref, one for Decay.

So i "measured" between Decay (ROSC) poti and UMDT instead of ground.

Here a picture of my driver:

[reprap.org]

Instantly when touching the pin with the measuring device, I heard the unplugging sound from Windows - same as when you unplug your USB Stick.

now only the middle green LED keeps flashing and my PC will not recognize the board anymore :-(


What could i potentially have damaged?

Maybe killed the bootloader? need to reflash the board in the best case scenario?

I do have an AVR Programmer here so i would be able to flash a bootloader on there if i can get the board to respond via miso/mosi etc. pins.


I just feel like i might have fried more

Alex.

Have you tried unplugging the RAMPS, to see whether the PC will recognise the Arduino by itself?

I hate having to twiddle pots on stepper motor drivers and mess around with multimeters to set the current, I much prefer modern boards that let you change the stepper motor current in configuration files, or better still, with gcodes - [reprap.org])..

Edited 1 time(s). Last edit at 02/20/2015 06:43AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Bootloader isn't responsible for the Arduino to be recognized by the PC. It's the USB-TTL chip on the Arduino.

I wasn't aware one could mess up with adjusting the trimpots, that's usually dead simple. I'd disconnect RAMPS from the Arduino now and try wether you can use the Arduino alone, uploading an example sketch.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

thx for your answers - i will try as suggested.
I did succesfully adjust the trimpots earlier - which alone is of course easy as pie.

but to be on the safe side I wanted to measure what i am doing and calculate the reslting Amperes the motors can get.

I did not know, that simply measuring ergo holding the contacts of the multimeter against the wrong pins coul actually destroy/damage some components.

I am well aware of the fact, that when you touch/short several pins with a metal screwdriver it can damage something, but with the measuring tip of my multimeter I did not touch several pins at once, i simply held one onto the trimpot the other one on the wrong pin.

And since I have mounted my board upside down on the printer and my 4988 Stepsticks from gadget 3D do have 2 Trimpots I accedentaly chose the wrong one as it seems.

Alex
Ps:
Traumflug, du bist deutschsprachig, liege ich da richtig?

Alright - I disconnected the Ramps from the Arduino Board - plugged into my PC and it got immediately
recognized. Thinking this was a good sign I thought, maybe I have damaged one of the drivers I had measured.
so turning off the power i unplugged one of the A4988 Drivers, put the Ramps back ontop the Mega 2560 Board and voila the PC recognized my Board again!
All axes do move and I am quite happy I first tried to measure the fifth stepper which was for a future extruder upgrade with a second extruder.
oh well now I'll have to get a new A4988 if I upgrade to another E3D V6 - but those 7 or 8 € are ok I guess.


So in order to prevent this from happening again.
is there a safe way of measuring?

Any advice?

I now know for sure where the VRef trimpot is and which Pin resembles GND.
so I turn on the PSU, hold the positive side of my multimeter on the Vref Trimpot and the negative side on the side of the little GND labeled pin.
And I try not to accidentally touch another pin while doing so.

my multimeter is set to volts in the 20V range.
correct?

Any advice or suggestions?

Thanks in advance,
Alex

Edited 2 time(s). Last edit at 02/21/2015 07:59AM by Alexander1984.

Quote
Alexander1984
I did not know, that simply measuring ergo holding the contacts of the multimeter against the wrong pins coul actually destroy/damage some components.

Very likely something else went wrong. For example the meter set to current instead of voltage. Or touching more with the probe than what you wanted. In voltage mode, digital multimeters have some 10 to 100 megaohms internal resistance, close to impossible to damage something with this.

If your controller is mounted upside down, turn the printer upside down, too. For adjusting current, motors don't have to move; being turned on, not moving is sufficient.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

I did not know that having my multimeter set to current instead of voltage could cause
damage. I might have touched some other pin with the probe - i guess I am not 100% sure.

so for next measurement I unplug all motor drivers which sit next to it and try to isolate neighbor-pins with small pieces of tape. That should ensure me not shorting anything.

guess there is a lot of "learning it the hard way" for a hobbyist making his way into
the subject called 3D-printing.

thx for advice,
Alex

Edited 1 time(s). Last edit at 02/21/2015 10:41AM by Alexander1984.

Quote
Alexander1984
so for next measurement I unplug all motor drivers which sit next to it and try to isolate neighbor-pins with small pieces of tape. That should ensure me not shorting anything.

Like with unplugging steppers, make sure to power down before unplugging stepper drivers. Not doing so creates a circuitry similar to the one operating the spark plugs in a car.

Edited 1 time(s). Last edit at 02/22/2015 07:02AM by Traumflug.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

thanks to good support here everything is up and working again!

I shut down and powered up again between each stepper driver i tested.
So basically i only had one stepper driver inserted - adjusted the V-ref accordingly, switched the power off, unplugged stepper driver -> inserted ne stepper driver, checked Vref---and so on.

Did not have any missed steps since.
Let`s hope it is fixed.

Alex