MP6500 - stepper motor driver 35V / 2.5A - with analog current control - Pololu 2966

The MP6500 stepper motor driver allows you to control a stepper motor with a device that can generate logic states, e.g. Arduino, STM32Discovoery, Raspberry Pi or any other microcontroller. The Pololu module is very easy to use. In order to rotate the motor by one step, you need to send a high state (logic one) to the STEP pin, the next sequence of zero and one will move the motor by the next step and so on. The selection of the direction is done by giving the appropriate state to the DIR pin (e.g. low state - clockwise rotation, high state - anticlockwise rotation). The controller also has the ability to select the resolution of motor operation.

A voltage in the range of 2.5 V to 5 V is required to supply the logic part of the module, which should be connected to the Sleep pin. The motor supply voltage from 4.5 V to 35 V is applied to the VMOT pin. The circuit can be used to control motors with a nominal voltage lower than the required 4.5 V. For this purpose, the maximum current consumption must be limited so as not to exceed the allowable motor current. For example, for a motor with a resistance of 5 Ω per coil and a current consumption of 1 A, the nominal supply voltage is 5 V. When supplied with 12 V, the current should be limited so that it does not exceed 1 A.

One pulse on the STEP pin causes one step of the motor in the direction selected by giving the corresponding logic state to the DIR pin. If the motor is to spin in one direction only, the DIR pin can be left disconnected.

The chip has two different inputs to control the power supply: SLEEP and ENBL their description can be found in the documentation. Note that the controller pulls both of these pins through internal 500 kΩ pull-down resistors. The default SLEEP state prevents the motor from running, a high state must be applied to it (it can be connected directly to a 2.5 to 5 V logic supply or it can be controlled by connecting to a digital MCU output). The default state of ENBL is controller on, it can be disconnected.

The FAULT output turns off when the F and H bridges are disabled due to current protection, overvoltage protection, thermal shutdown, or voltage dropout protection. It connects to the SLEEP pin via a 10 kΩ resistor, which functions similarly to FAULT. When SLEEP has a high state, it is not necessary to connect FAULT.

The circuit can be used to control motors with a nominal voltage lower than the required 4.5 V. To dothis , limit the maximum current draw using a potentiometer so that the motor current is not exceeded. For example, for a motor with a resistance of 5 Ω per coil and a current consumption of 1 A, the nominal supply voltage is 5 V. When supplied with 12 V, the current must be limited so that it does not exceed 1 A.

The MP6500 module allows for active current limiting using a potentiometer. One way of limiting is to set the controller to full step mode and measure the current flowing through one coil without providing a signal to the STEP input. The measured current is 70% of the set limit (both coils are always on and limited to 70% in full step mode). Another way is to measure the voltage at the VREF pinout (marked with a circle on the PCB) and calculate the current limit (the measurement resistors are 0.05Ω). More details in MP6500 chip documentation.

The board is designed to dissipate heat at a current consumption of about 1.8 A per coil. If the current will be much higher, you should use an external heat sink for which you can use thermally conductive glue.