MD25 - Dual 12Volt 2.8Amp H Bridge Motor Drive
For 2 EMG30 motors
Devantech
Designed to work with the EMG30 gear-motor with encoders, the MD25 will drive two motors. Controllled by Serial or the I2C Interface. Two modes of operation, direct individual control of the motors or the ability to send a speed and a turn commands.
Overview
The MD25 is a robust I2C or serial, dual motor driver, designed for use with EMG30 motors. Main features are:
- Reads motors encoders and provides counts for determining distance traveled and direction.
- Drives two motors with independent or combined control.
- Motor current is readable.
- Only 12v is required to power the module.
- Onboard 5v regulator can supply up to 1A peak, 300mA continuously to external circuitry.
- Steering feature, motors can be commanded to turn by sent value.
- Variable acceleration and power regulation also included.
Electrical Specifications
- Voltage - 12v only. The 5v for the logic supplied from an on-board regulator, 300mA available for your own circuits.
- Current - Up to 2.8A for each motor.
- Encoder - Processes quadrature encoder inputs from motor. 360 counts per wheel turn when used with the EMG30.
Connections
Power Supply
Two cables with 12V power input for the board must be connected as indicated in the image above. This is the only power supply for the board. Supplying 12V to the 5V output terminal of MD25 could destroy the module. Vcc is the 5V output from the onboard 7805 regulator.
Motor Voltage
The MD25 is designed to work with a 12v battery. In practical terms, this means the 9v-14v swing of a flat/charging 12v battery is fine. Much below 9v and the under-voltage protection will prevent any drive to the motors.
Motor Noise Suppression
When using our EMG30 encoded motors, you will find that a 10n noise suppression capacitor has already been fitted. Other motors may require suppression. This is easily achieved by the addition of a 10n snubbing capacitor across the motors. The capacitor should also be capable of handling a voltage of twice the drive voltage to the motor.
4 pin connection overview
Connect up to 4 pin cables to the MD25. Your control device might have VCC, GND, TXD and RXD.
Connect RXD with Tx.
Connect TXD with Rx.
Connect GROUND with Ground.
Connect VCC with Vcc.
4 pin connection to Robospine
Connect 3 pin cables between Robospine and MD25 for example using the 4-WAY-SPLIT-MOLEX cable with the 4 way 0.1" pitch connector on the Robospine side and the four individul pin connectors on the MD25 side.
Do not connect 5V.
Connect SDA with SDA.
Connect SCL with SCL.
Connect GROUND with Ground.
Mode of operation: Serial / I2C Select - Important Note
For serial connections, jumpers are installed according to the clock speed on the serical / I2C Select. Serial connections are made with cables from Rx (receiver) to Tx (transfer) and from Tx (transfer) to Rx (receiver). For clear explanation please see the Manufacturer's data linked below.
For I2C connection, on MD25 board go to the Serial/I2C Select and make sure that you have not installed any jumpers on this Select (if any connections are made, remove the jumper). Make SDA & SCL connections with cables from SDA (serial data) to SDA (serial data) and from SCL (serial clock) to SCL (serial clock). For clear explanation regarding I2C connection please see the Manufacturer's data linked below.
I2C commands in Linux
Install I2C on your computer and enable it. Then use for example the following simple commands:
~# i2cdetect -y 0
This command detects the devices (if you're using multiple devices, mention the number of devices which are connected in place of '0').
~# i2cset -y 0 xxxx 255
This simple command writes the byte value 255 to the I2C device at address xxxx hex on the i2c bus 0 (/dev/i2c-0).
~# i2cget -y 0 xxxx
This command reads a byte from an I2C device at address xxxx hex on the i2c bus 0 (/dev/i2c-0).
Testing MD25 with Raspberry Pi 4
Raspberry Pi 4 has various pins such as GPIO, SPI and I2C (inter-integrated circuit).
For testing purposes a 12V connection is not required. The Rasperry Pi can supply the MD25 with power. Simply connect 4 pins by cable between Raspberry Pi 4 and MD25:
Connect 5V Pin 2 or 5V Pin 4 at Pi to Vcc at MD25 (red cable in image)
Connect GPIO 2 SDA (data) at Pi with SDA at MD25 (green cable in image)
Connect GPIO 3 SCL (clock) with SCL at MD25 (blue cable in image)
Connect Pin 6 GROUND at Pi with Ground at MD25. (black cable in image)
Now follow the steps below in the command line of the Raspberry Pi 4:
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install i2c-tools
sudo raspi-config
enable I2C in the menue
i2cdetect -l
i2cdetect -y 1
The adress of the MD25 should be shown as HEX value such as 0x58. If it is not shown, then the MD25 is probably disconnected. If disconnected, check connections and reboot the Pi.
i2cget -y 1 0x58 10
to read supply voltage
result: 0x76, which means 118 (divided by 10 = 11.8 V from the Raspberry Pi 4)
i2cget -y 1 0x58 13
to read the Software Revision Number of MD25
result: 0x04, which means 4
i2cget -y 1 0x58 15
to read the mode of operation
result: 0x00, which means 0 (= default setting)
Testing MD25 with EMG30 motor and Raspberry Pi 4
For testing the MD25 with a EMG30 motor, connect for example a 12V battery to the MD25 board.
Now follow the steps below in the command line of the Raspberry Pi 4:
i2cset -y 1 0x58 0 0
to set the motor 1 (EMG30) speed in the byte value 0 (full reverse)
i2cset -y 1 0x58 0 255
to set the motor 1 (EMG30) speed in the byte value 255 (full forward)
Leds
The Red Power Led indicates power is applied to the module. A Green Led indicates communication activity with the MD25. In I2C mode the green led will also initially flash the address it has been set to. See I2C documentation for further details.
Board dimensions
- Size - 110mm x 52mm x 25mm
Frequently Asked Questions
Customer: "Will the MD25 motor driver work only with single EMG30 motor?"
Manufacturer: "Yes, the MD25 will drive one motor with no issues."
Manufacturer's data
Accessories
4-Way split Cable with Molex connector, 30 cm in length
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Product information for: MD25 - 12V 2.8A Dual H-Bridge Motor Driver
Publishing date (date of last technical specification): 2010-11-10
Length: 110 mm
Width: 52 mm
Height: 25 mm
Weight: 22 g
Shipping weight: 50 g
Manufacturer: Devantech
Brand: ROBOT ELECTRONICS
Article number: DEV-MD25
Manufacturer's part number: MD25
The article MD25 - 12V 2.8A Dual H-Bridge Motor Driver is listed in the following categories:
Drives > Motor control
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updated: 29.08.2022
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About ROBOT ELECTRONICS
ROBOT ELECTRONICS is a brand by English manufacturer Devantech Ltd., based in Norfolk. Product range comprises sensors, in particular ultrasonic or compass, servocontrollers as well as small robot drive systems or relay modules with various interfaces. Sensors are produced in England and are of consistently high quality.
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