Originally shared by Mongrel Shark
This video shows how to test a RAMPS 1.4 Arduino Shield with a4899 (pololu) Stepper Drivers. These Open Source boards are commonly used for 3d printers and CNC devices.
I show what changing the jumper pins does. What to look for to know its working, using motor or oscilloscope as the tester. I show what a damaged stepper driver will do as well as show the output waveform on the o’scope.
I also look at the MOSFET switching for extruder and heat bed. My heat bed was not working, because I did not hook up the separate power input for the heat bed. With a second 12v in the appropriate place, the heat bed MOSFET appears to be working as required.
Test code is available here: http://reprap.org/mediawiki/images/3/34/RAMPSTestCode.pde
Or from the link on the RAMPS pages http://reprap.org/wiki/RAMPS_1.4
Just a little reminder for keeping your stepper drivers happy: Do not connect or disconnect steppers while the board is powered up. I’ve blown out two sets of drivers like this until i figured out that they didn’t like it too much.
Also, pretty much all modern firmwares allow you to select the RAMPS by simply changing a #define.
I was getting more issues starting the board with steppers connected. Seems thats what killed the pololu’s… Or they where shipped faulty… If you look at the a4988 schematics, you can see there is supposed to be inductive repression to deal with hot connect/disconnect. The Pololu brand ones are covered in cheap parts and crappy soldering… The after market ones are much better. miss less steps, better layout and are a third the price. Win win win
What do you mean “Select the RAMPS”??? This is test firmware. Purely for testing the ramps board works, and has no broken components or bad solders.
You’re right, it somehow skipped my mind that you weren’t using a real firmware. It just looked an awful lot like you were copying over just the #defines for the pins.
In my experience, there is very little difference in the build quality of the stepper drivers. I’ve had genuine Pololu A4988 and DRV8825 boards, Stepsticks from the Netherlands and GEEEtech boards from China. The main differences are that Stepstick-based boards are limited to about 1A in hardware, while the Pololu-based designs go up to 2A with sufficient cooling. The other thing, which @nop_head documented, is one resistor which determines microstepping behavior and, on the genuine board, is best swapped out.
Do you have a link to @nop_head 's document? Those resistors could be the cause of the failed b channel. I never liked them… Been meaning to look into replacing them.
The pololu’s we received have some really rough solder work, and I think some of the caps are damaged, some places the board has clearly been cooked… They are just cheap and nasty looking compared to the cheaper alternative. Pics of older ones dont have this problem. I think with all the reprappers ordering tons of them, standards have dropped in order to meet demand. I find the aftermarket ones better in every way. The lower amps is not likely to be a problem. I can always up the voltage, as I put 35v caps on my RAMPS board… Although with the torque I’m seeing, I dont think I will drive any past half an amp.