- James DonnellyParticipantSeptember 23, 2016 at 6:07 amPost count: 48
Was trying to replace a power resistor in an old hot end, and something fried after heating a few degrees. I presumed the power resistor, but I then found that the Arduino board was no longer detected by Windows. It had the solid yellow light on power up. I’ve had this before, so I know this means dead Arduino.
So I plugged in a replacement new Arduino, with a replacement ramps 1.4 board, located the step sticks from before, and fed the 12v power in. Instantly heard the same crackling noise and saw the same blue smoke as when the first boards fried.
I guess the stepsticks were probably shorting out from damage the first time around, because the other components in the system were new at that point.
I’ve ordered a new Arduino, Ramps board, and set of stepper drivers, but for now I’m questioning my testing process as I don’t want to fry any more stuff.
Sanity check: I plug a new ramps board into a new Arduino with new stepper drivers on and power it up. If it doesn’t fry, that means the stepper drivers were to blame for the second frying episode. If it fries again, I don’t know what the hell to do next! My PSU is putting out 12v and seems fine.
Jamesvicious1KeymasterSeptember 23, 2016 at 7:38 amPost count: 2677
I have fried a bunch of drivers, by accidentally unplugging steppers while in motion, but never a board. What went bad? The usual suspects on the arduino are the voltage regulators, and on the ramps usually the mosfets. Anything else you should be able to see.James DonnellyParticipantSeptember 23, 2016 at 7:54 amPost count: 48
I really don’t know. If I was guessing I’d say the IC received some juice.
Only thing I could see is that an SMD resistor (third from left in row of 3 above the clock/crystal) looked like the solder had boiled off, and the resistor came off when touched.JohnParticipantSeptember 23, 2016 at 9:15 amPost count: 128
plug in the “Smoked” arduinos to the computer and next to the USB connection are two small IC’s. put your fingers on them. After just a few seconds they should get very hot. at this point, unplug the arduino. If those ic’s got hot, then what happened is that you put too much current through the regulator. you can change them out (see my video on doing that under “random/off topic”) and your arduino is good as new. it’s fairly difficult to really destroy the arduinos because the regulators should fail well before any permanent damage is done.
I think it’s called “how to solder SMT or mad soldering skills” or something like that… I’ve fried a fair amount of regulators and have yet to really destroy an arduino…JohnParticipantSeptember 23, 2016 at 9:21 amPost count: 128
oh… and for a testing methodology… if you are replacing things like power resistors or places where a lot of current should flow, you can use a current limited supply or a smallish buck/boost convertor just in front of your arduino/ramps. They will undervolt and turn off before you burn things out. I’ll do a basic calculation of the current that is expected to flow in the device when heating up (V=IR, V/R=I) and them make sure that my buck/boost or current limited supply can produce about that much, but not very much more before it shuts down.
alternately, you can also plug the things in with your fingers on either the power mosfet or the regulator and see if it gets really hot right away and immediately unplug it.
Both options will help you save the devices before you let the smoke out.James DonnellyParticipantSeptember 28, 2016 at 2:26 pmPost count: 48
It was the stepper drivers.
John, those two ICs on the Arduino are not getting hot on either of my two broken Arduinos. I didn’t get around to checking the mosfets on the broken RAMPS boards yet. They are in a bag marked broken for now!
My mistake was that I had damaged the stepper drivers, and I fitted them on the new Arduino/RAMPS, which broke the new boards, just like the first ones.
On my third set of boards now, but with new stepper drivers, and all is fine.
Thanks for all the input, expensive mistake but I’ll put it down to experience.
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