Optimum Current for A4988 Drivers

Hi Everyone,

what is the optimum current for A4988 stepper motor drivers? I've not been find anything about it.

I am using nema 17 stepper on my printer.The motors data sheets says rated current is 0.84A.



i measured my drivers current is about 0.5 A , but my extruder motor really hot and skip steps. After that i realized the drivers current may be the problem. some blogs tells me 0.72 or lower Amps is good, but i have problem wtih 0.5 Amps.

And i saw in some video, he setted the current is 0.3A,


what is the real and optimum current value?What is your direct drive extruder motor current??


Check the photo below, i guess my problem is current problem. sometimes during the extruding, the extruder miss steps for a while and then if I help it by hand for a while, it recovers and get fine again


0.5 A to much for my extruder motor and motor goes hot and skip stepping, motor goes to the shut down for a while and start again. in the meantime filament does not pull by the motor and we see the bad layers? Am i right for you??

Edited 1 time(s). Last edit at 09/06/2014 04:41PM by RDEng.

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Custom 3D Printer,

Mechanical Engineer

Are you measuring 0.5 amps, or 0.5 VOLTS when you are calibrating the stepper drivers? I know that my stepper motors were happy with the trim pot set at 0.4 volts...which results in about 1 amp of current to the steppers per this formula:

http://reprap.org/wiki/Pololu_stepper_driver_board#A4988_and_similar

If you are measuring 0.5 volts, then the steppers are really seeing 1.25 amps, which probably explains why they are overheating.....

Hi vreihen,


I measured the 0.5 amps. I did not measure the volts. do you think it is necessary?

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Custom 3D Printer,

Mechanical Engineer

All of the online directions that I have ever read for tuning A4988 stepper drivers specify the VOLTS reading between the center of the adjustment potentiometer and ground, with the conversion formulas in the link above to convert the measured voltage into the amperage output to the stepper motor:



A frequent gotcha for people who are learning electronics when building their first printer is to confuse volts and amps. Measuring amperage requires cutting/breaking a wire between the stepper driver and motor and inserting the multimeter in *series* into the circuit, and with many multimeters also requires using special "amps" terminals versus the volts/ohms terminals commonly used:



I do not know your level of experience with electricity and electronics, and apologize in advance if you already know this stuff and measured correctly. My *geared* NEMA 17 stepper motor driving a long Bowden extruder tube with an Mk8 hobbed pulley was perfectly happy with the A4988's set at 0.4 volts (which puts out 1.0 amps to the steppers). I don't have personal experience with a direct-drive extruder, but my first impression from reading that your direct-drive extruder is overheating at only 0.5 amps is that you made the common measuring mistake and are really driving 1.25 amps into your 0.84 amp stepper (meter reading 0.50 VOLTS between the trim pot and ground).....