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- Power supply voltage: 8.2 V - 45 V
- Continuous current behind the coil: 0,75 A
- Maximum instantaneous current per coil: 1,2 A
- The supply voltage of the logical part: 2.5 V - 5.25 V
- Resolution: 1, 1/2, 1/4, 1/8, 1/16, and 1/32 steps
Based on the DRV8824 controller from Texas Instruments, the module allows you to control a stepper motor with a maximum current consumption of up to 0.75A per coil (using cooling up to 1.2A). It is powered from 8.2V to 45V. Before use, we recommend that you read the DRV8824 controller documentation. Below are some of the main product features:
- The module has a simple interface for step and directional control
- It can work in six modes: full step, half step, 1/4 step, 1/8 step, 1/16 step and 1/32 step
- Provides control of the maximum motor current by means of a potentiometer, which allows the use of higher than rated power supply voltages for stepper motors, so you can get a higher step speed
- Motors can be supplied with voltages from 8.2 V to 45 V
- Maximum current consumption is 1.2 A ( 0.75 A without external cooling)
- Thanks to the integrated voltage regulator, the user does not have to provide additional power to the logical part.
- The DRV8824 works with systems with both 3.3 V and 5 V logical part voltage.
- It has protection against too high a current and temperature and short-circuit protection as well as a start blocking system at too low a supply voltage.
- In order to increase the heat-releasing surface, the tile was made in four-layer technology with a thicker copper cover.
- A bare ground field on the underside, allowing the solder to solder the cooling elements
- The module is compatible in terms of size and output with the A4988 driver-based system
The kit contains all the necessary elements to connect the controller - module and connectors for self soldering. On request, we can supply the system with soldered connectors. For this purpose, please leave the information in the commentary to the order.
Connection of the controller
To control the bipolar stepper motor, connect the system as shown in the figure below. The controller also allows you to work with some unipolar motors, see the manual for details.
One pulse given on the STEP pin causes one motor step in the direction selected by giving the appropriate logical state on the DIR pin. The STEP and DIR outputs are not pulled up internally. If the motor is to turn in only one direction, the DIR pin can be permanently connected to VCC or GND.
The system has three more inputs to control power consumption: RESET SLP and EN, for a description see the documentation. Please note that these outputs are not connected to anything. If they will not be used to control power consumption modes, they must be externally pulled to the power supply voltage (state high - logical one from 2.2 V to 5.5 V).
The DRV8824 controller also has a lead marked as FAULT. In the low state (logical zero) it signals the occurrence of irregularities in the system operation, e.g. activation of one of the protections. On the board, the output has been connected to the SLEEP pin, so the high state on the SLEEP pin pulls also FAULT to VCC (pull-up). Thanks to the use of a serial resistor, the FAULT output can also be connected to the VCC, which makes the pin-compatible with the A4988 version.
The system can be supplied with voltage from 8.2V to 45V connected between VMOT (+) and GND (-) pins. The voltage should be filtered through an external capacitor placed as close to the controller board as possible. Its capacity depends on the maximum current drawn by the motor.
In some conditions even a relatively low power supply voltage may cause pins with a high amplitude exceeding the 45 V limit. Such situation leads to permanent damage to the system. One of the ways to avoid this problem is to place the capacitor (at least 47 uF) as close as possible to the VMOT and GND pins of the controller module.
Connecting and disconnecting the motor while the controller is on can damage the system.
A micro-step controller such as the DRV8824 allows the motor to work with high resolution up to 1/32 steps. Step size is selected using the MODE1, MODE1 and MODE2 inputs - available modes are shown in the table below. By default, all three outputs are pulled to ground by a 100kΩ pull-down resistor. Leaving them unconnected means that the mode of operation with full step is selected. For example, when using a motor with a resolution of 200 steps per revolution, selecting a ¼ step mode means working with a resolution of 800 positions per revolution.
To maintain a high switching speed of the steps, a higher motor supply voltage than the nominal one can be used. Only limit the maximum current (to the motor's nominal value) flowing through the coils.
The module allows you to actively limit the current with a potentiometer. One of the ways to introduce the limitation is to set the controller to full step mode and to measure the current flowing through one coil without giving 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 REF output (marked with a circle on the PCB) and calculate the current limit (measuring resistors are 0.330Ω). The current limit can be calculated from the formula:
Current Limit = VREF * 0.61
For example, if the motor can draw up to a maximum of 0.5 A, the reference voltage on the VREF pin should be 0.82 V.
The plate is designed to dissipate heat at a current consumption of approximately 0.5A per coil. If the current is much higher, an external heat sink should be used, which can be mounted with thermally conductive adhesive.
The system contains the necessary passive components for proper operation of the controller. The connection diagram is shown in the drawings below.
Main differences from the A4888 version
The DRV8824 is designed to be compatible with the A4988 version. The tiles have the same shape, size and layout. However, there are several differences between them:
- The pin used as power supply voltage for the logical part of the A4988 has been replaced by the FAULT pin because the DRV8825 does not require any additional power supply. The FAULT has been connected by a protection resistor, so it can be successfully used in a system designed for the A4988 module, where this pin will be given the supply voltage of the logical part (2.2V to 5.5V).
- In the DRV8824 module the SLEEP pin is not pulled up by default (via pull-up resistor) to the power supply, it is connected to the FAULT output via a 10k resistor. In circuits designed for A4988, a 10k resistor pulls the SLEEP to the power supply through the supply voltage of the logical part connected to FAULT, setting it to high.
- The maximum current limiting potentiometer for motors is located elsewhere
- The DRV8824 allows you to operate in 1/32 step mode, while the A4988 operated to 1/16 step
- The DRV8824 has a lower current capacity but has a larger supply voltage range up to 45 V (A4988 up to 35 V), which also makes it less susceptible to short, high amplitude electric pulses (so-called pins)
- The outputs have different names, but have the same function