RepRap Champion 5 PCS Allegro A4988 StepStick Stepper Motor Drivers for 3D Printer Electronics, CNC Machine or Robotics

These little stepper motor driver boards work quite well. I used them to replace some similar driver boards on my 3D printer that were having some issues.One thing to be aware of is that these boards have a sense resistor (Rs) value of 0.100 ohms instead of the 0.050 ohms that the authentic Pololu boards have. This means that when you are setting the reference voltage (Vref) for the current limiter, you must set it to twice that of the Pololu boards. So if you are replacing a module from a different manufacturer, be sure to compare sense resistor values before setting it.The current limiter value in amps is:Ilimit = Vref/(8*Rs)Where Vref is the voltage from the wiper (top outer shell) of the adjustment pot to ground. This can be easily measured while setting it by attaching a volt meter probe to the miniature screwdriver you are adjusting it with and with the other meter probe connected to the ground pin (the lower right-hand pin when you have the board turned so that the pot is at the bottom and are looking down on it from the top side).Rs (sense resistor) is the slightly wider surface mount resistors on the board and are labeled "R100" on this board (R050 on an authentic Pololu). There are two of the sense resistors on the board, both of the same value.Also, the voltage divider configuration with the pot on this board uses a 30k resistor in series with the 10k pot, whereas the authentic Pololu board is 20k resistor with the 10k pot. Since the fixed resistor is in series with the 10k pot, that means that on this board, the pot will adjust Vref from 0 to 1/4th the Vcc value (Vcc * 10k/(10k+30k)), whereas the authentic Pololu can be adjusted from 0 to 1/3rd of Vcc (Vcc * 10k/(10k+20k)).So, while the sense resistor configuration on this board requires you to set a Vref that's twice that of the authentic Pololu board, you won't have quite as much range on the Vref setting as the authentic Pololu to do that. That means the highest current limit value that can be set on this board is about 1.56 Amps. Whereas on the "real" Pololu, it can be set to a whopping 4.2 Amps.In reality, this board is much better configured, as the A4988 driver chip is only rated to a maximum of 2 Amps and most cases thermal limits keep you from being able to achieve quite that even. So to only be configurable for 1.5 Amps is much more reasonable than being able to set it to 4 Amps, which effectively disables the current limiter as the thermal limiter will stop you long before that.So for that reason, I actually like this board better than "the real thing", as it gives you a finer pitched control setting for the current limiter that isn't quite as touchy to set. Clockwise increases the current limit and counterclockwise decreases it.Some similar driver boards have some minor clearance issues with the heatsink and surface mounted parts. I was pleased to see that on this board, while they are really close, it doesn't have any issues. There is a slight overlap between a couple surface mount pieces and the heatsink, but the double-sided tape on the heatsink is enough to shield it from shorting.Overall, I'm well pleased with these drivers and plan to get some more of them for several additional projects.

With these popular Stepstick drivers I use simplified stepper current adjustment procedure:Set pot to minimum current, for start, and inscrease it a little by little until stepper will start getting warn.You adjustment is done.

These drivers make the steppers so loud i dont want to be in my house when the printer is on.

Impossible to calibrate

Work for me as well as Pololu units I destroyed.

Working fine so far. Bought to replace a bad stepper on my 3D printer, and am using the rest as backup just in case.

Came quickly and works well was a total life saver when my Z axis went out on my 3d printer.

Good quality cheap drivers. Calibration to your stepper is necessary.