The A4988 is a Stepper Motor Driver board that has on a A4988_chip that enables control of stepper motors through arduino type programming firmware and software.
The A4988 is an utterly tested and proven solution to drive stepper motors in RepRap 3D printers, and this fact should not be overlooked. As long as the following three conditions are met, these Made in China Allegro A4988 stepper driver boards seem to be bullet-proof workhorses:
- The stepper driver boards should not be inserted backwards in their respective slots on the controller board (Doh!).
- The stepper cables should not be disconnected from the boards while powered on.
- Proper airflow (i.e. active cooling or in other words, a fan) should be provided. quote
It is one of the two most popular ad,d-on stepper motor driver boards. The alternative DRV8825 board, with increased 1/32 step mode is slightly more expensive.
The following table compares Made in China A4988 Stepper driver boards vs DRV8825 ones, for RepRap use:
|Availability||very widely available||widely available|
|Approx. price||$6.80 / 5 pieces||$10 / 5 pieces|
|Max. theoretical current||2A||2.5A|
|PCB color||Green / Red||Purple|
|Stepper current adjust. trimpot||Yes, near Dir pin||Yes, near En pin|
|Typical Rs value|| 0.05 Ohm or
0.1 Ohm or
|Vref formula (*)||I_TripMax= Vref/(8*Rs)||I_TripMax= Vref/(5*Rs)|
|Thermal Overload Protection (**)||Yes||Yes|
|Small heatsink included (***)||Almost always||Sometimes not|
|Active cooling required?||Recommended||Recommended|
|IC packaging||5x5mm 28-lead QFN||9.7x6.4mm 28HTSSOP|
Note that some important technical characteristics from the respective datasheets of the ICs are not directly comparable. For example, the DRV8825 is fully specified in terms of thermal characteristics, the A4988 is not. Another important characteristic that unfortunately is not directly comparable is RDSon, which is specified at different current levels in the respective IC datasheets.