DRV8825 stepper motor driver - 2.2A 45V - StepStick RAMPS

The stepper motor controller based on the DRV8825 chip allows controlling a motor with a current consumption of up to 1.5 A (with cooling up to 2.2 A) per coil, when supplied with a voltage of up to 45 V. It has six control modes: full step, 1/2, 1/4, 1/8, 1/16 and 1/32 step.

Product features

• This module is powered by a voltage in the range of 8.2V to 45V. We recommend reading the DRV8825 controller documentation before use.
• Simple step and direction control interface
• Ability to operate in six modes: full-step, half-step, 1/4-step, 1/8-step, 1/16-step, and 1/32-step
• Control the maximum motor current with a potentiometer, this allows you to use a voltage higher than the rated voltage to supply power to the motors, so you can get a higher step speed
• Motors can be supplied with voltage from 8.2V to 45V
• Current consumption up to 2.2A (1.5A without external cooling)
• Thanks to the integrated voltage regulator, the user does not need to supply additional power to the logic part.
• DRV8824 works with circuits with both 3.3V and 5V logic part voltages.
• It has over-current and over-temperature protection, as well as a system that blocks startup when the supply voltage is too low
• To increase the heat transfer surface area, the board has been made using four-layer technology with a thicker copper cover
• Exposed ground field on the underside, allowing soldering of cooling components
• The module is compatible, in terms of size and pinout, with a circuit based on a controller

Note! Connecting and disconnecting the motor while the controller is on can damage the system.

Technical data

• Supply voltage: 8.2 V - 45 V
• Continuous current per coil: 1,5 A
• Maximum instantaneous current per coil: 2,2 A
• Supply voltage of the logic part: 2.5 V - 5.25 V
• Resolution: 1, 1/2, 1/4, 1/8, 1/16, and 1/32 steps

Included

• DRV8825 controller module - with soldered feet
• Radiator

Detailed description of the controller

Control

One pulse applied to the STEP pin results in one motor step in the direction selected by applying the appropriate logic state (high or low) to the DIR lead. STEP and DIR pins are not internally pulled up. If the motor is to spin in one direction only, the DIR pin can be permanently connected to VCC or GND.

The circuit has three more inputs to control power consumption: RESET, SLP and EN, their description can be found in the documentation. Note that these leads are not connected to anything. If they will not be used, they should be externally pulled up to the supply voltage (give a high state - a logical one in the range of 2.2V to 5.5V).

The DRV8825 controller also has a lead marked FAULT. Low state (logical zero) signals the appearance of irregularities in the operation of the system, such as tripping one of the protections. On the board, the lead was connected to the SLEEP pin, so applying a high state to the SLEEP pin pulls up to VCC (pull-up) also FAULT. Thanks to the serial protection resistor, the FAULT lead can also be connected to VCC voltage, making the module pin-compatible with the A4988 version.

Power supply

The circuit can be powered by a voltage from 8.2V to 45V connected between the VMOT (+) and GND (-) pins. The voltage should be filtered through an external capacitor placed as close as possible to the controller board. Its capacity depends on the maximum current drawn by the motor.

Resolution

A microstep controller such as the DRV8825 allows the motor to operate with high resolution up to 1/32 of a step. Step size is selected using the MODE1, MODE1 and MODE2 inputs - the available modes are shown in the table below. By default, all three leads are pulled down to ground through a (pull-down) 100kΩ resistor. Leaving them unconnected therefore means selecting full step mode. For example, when using a motor with a resolution of 200 steps per revolution, selecting the ¼ step mode means working at a resolution of 800 positions per revolution.

Current limitation

To maintain high switching speed of steps, a higher motor supply voltage than the nominal one can be used. Only limit the maximum current flowing through the coils to the catalog value of the motor.

The module allows active current limitation using a potentiometer. One way to implement the limitation is to set the controller to full step mode and measure the current flowing through one coil without applying a signal to the STEP input. 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 REF lead (marked with a circle on the PCB) and calculate the current limit (the measurement resistors are 0.1Ω). The current limit can be calculated from the formula: Current Limit = VREF × 2. For example, if the motor can draw up to 1A maximum, the reference voltage on the VREF pin should be 0.5V.

Heat dissipation

The board is designed to be able to dissipate heat with a continuous current draw of about 1.5A per coil. If the current will be much higher, an external heat sink should be used, which can be mounted with thermally conductive adhesive.

The main differences from the A4888 version

The DRV8825 module is designed to be compatible with the version based on the A4988 chip. The boards have the same shape, size and distribution of leads. However, there are several differences between the two:

• The pin used as a supply voltage for the logic part of the A4988 has been replaced by the FAULT pin, since the DRV8825 does not require additional power supply. FAULT was connected through a protection resistor, so it can successfully be used in a system designed for the A4988 module, where the supply voltage of the logic part (2.2V to 5.5V) will be applied to this pin.
• In the DRV8825 module, the SLEEP pin is not pulled up to the power supply by default, it was connected to the FAULT pin through a 10k resistor. In circuits designed for the A4988 chip, through the supply voltage of the logic part connected to FAULT, a 10k resistor pulls up SLEEP to the supply voltage, setting the state high.
• The potentiometer that limits the maximum current for motors is located elsewhere
• The DRV8825 allows operation in 1/32 step mode, while the A4988 worked up to 1/16 step
• The DRV8825 has a larger supply voltage range of up to 45 V (the A4988 up to 35 V), which also makes it less susceptible to short, high-amplitude electrical pulses (known as pins)
• The leads have different names, but perform the same function

Controller diagram