A4988 - stepper motor driver RepRap 35V/2A - Pololu 1182

The system allows you to control a stepper motor using a device that allows you to generate the logical states, for example,Arduino,STM32Discovoery,the Raspberry Pi or of anymicrocontroller. The Pololu module is characterized by a very simple operation. In order to rotate the motor one step further, you must specify the STEP with high state (logical one), another sequence of zeros and ones, moves the motor one step further, etc. The choice of direction is accomplished by specifying the state on the DIR lead(e.g. low state - clockwise, high stae - counterclockwise). The driver also has the choice ofresolutionof operation of the engine.

To power the logic part of the module, you need the voltage which ranges from 3 V to 5.5 V, which should be brought to the pin VDD. The motor supply voltage is in the range from 8 V to 35 V is indicated on the pin VMOT.The system can control the engines with a nominal voltage lower than the required 8 V. In this case, it is necessaryto limit themaximum current consumption through the potentiometer, so as not to exceed the maximum voltage of the motor. For example, for a motor with a resistance of 5 Ωon one coil and a current consumption of 1 A, the nominal supply voltage of 5 V. Power with the voltage of 12 V to limit the current, so it does not exceed 1 A.

One pulse specified on thepin STEP causes one step of the motor in the direction selected by indicating the appropriate logic state on the pin DIR. Leads STEP and DIR are not internally pulled up. If the motor should only rotate in one direction, the DIR pin can be permanently connected to VCC or GND.

The system has three other inputs for monitoring power consumption: RESET SLP and EN and their description is indocumentation. Please note that the pin RESET is not pulled to anything. If not used, you can connect it to the adjacent pin SLEEP.

The system can be controlled by the engines with a nominal voltage lower than the required 8 V. In this case, it is necessaryto limit themaximum current consumption through the potentiometer, so as not to exceed the maximum voltage of the motor. For example, for a motor with a resistance of 5 Ωon one coil and a current consumption of 1 A, the nominal supply voltage of 5 V. Power with voltage of 12 V to limit the current, so it does not exceed 1 A.

The A4988 module allows for active current limitation with the potentiometer. One of the ways of the introduction of restriction is to set the driver to full step and measuring the current passing through one coil without indicating the signal at the input STEP. The measured current is 70% of the established limit (both coils are always on and limited to 70% in full step mode). Another way is to measure the voltage at lead REF (marked with a circle on the PCB), as well as the calculation of the current limit (measuring resistors have a value of 0.05Ω). More detail in thedocumentation for the A4988 chip.

The tile was designed so that it can dissipate heat when the current consumption is about 1A per coil. If the current is much higher, use an externalheatsink, to the assembly of which, can be used thermally conductive glue.