Sunday, March 14, 2010

lin nema 17

well, I hooked up the new nema 17 stepper i got from lin to the extruder board.....
nother blown board.....

Im having some difficulty understanding why they would blow the h-bridges like this. They are supposed to be rated at 2 amps and this stepper is not supposed to draw more than that but obviously it does. My next step is going to be two fold. Im going to desolder the h's and rewire the board to connect to a regular stepper board, then reprogram the firmware to drive the stepper that way.

The other half is to assemble the pololu boards i have into something resembling what adrian posted the other day. I already downloaded the mega code into my new mega board though i didnt try personalizing it to my hardware yet, just a test download realy.

also planning on cutting my aluminum build bed today. I have a lexan sheet in the mendel right now but that was mostly just for testing and calibration.


  1. It could be worth your while to put a 2A fuse in line with the motor supply to your driver. It oculd work out cheaper than the drivers to replace whilst you are fault finding.

    Another thing worth trying os to measure the winding resistance on our motors. The DC value will allow you to calculate (Ohms Law and all that stuff) what the peak current draw your steppers could make (worst case) at the voltage you are driving them with. (use supply value for worst case as the actual at the motor will be less due to voltage drop acros the driving circuitry).

    I don't know which dirvers you are using but many have a current limit (set by a varilable resistor) turn this to deliver minimum current and then increase gradualy until you get aceptable performance without excessively high stationary current. (if your motors or your bridges are getting too wamr reduce the current limit)

    A last tip, if you have a bench PSU with a current limit use this with the curent limit se to a useful and board preserving low value until you get the drivers to do their own limiting or you sort out what the problems are.

    All of the above will save you time and money when fualt finding.

    Hope this helps.

  2. If you used the makerbot extruder board like me, I had an h-bridge blow up too, purely from Back EMF, those chips are not very durable.

    I just happen to have a V1.2 stepper board spare, and have wired that up. Just fudging stupid Arduino code to work properly.

  3. yea, i would say its probably the back emf and yes it was the makerbot extruder board. i have desoldered one of the chips and soldered in a stepper board to it and now just have to rewrite the firmware for it