The Raspberry Pi or RBPi is an inexpensive, tiny single board computer running the Linux operating system. As such, the standalone RBPi is not suitable for running motors, but when combined with an expansion board such as the RasPiRobot Board, you can easily run DC motors as well as Stepper motors off the RBPi. For this, you must use the version 2 of the RasPiRobot or RRBv2 board. Please note you can run only 5V steppers with the RBPi RRBv2 combination, as this board does not support 12V motors.
In practice, the RRBv2 board sits over the RBPi fitting over the latter’s GPIO connector. The stepper motor wires connect to the RRBv2 board, using its L & R screw terminals. To do that, you must first strip the wire ends of their PVC insulation, until about 10 mm of bare copper wire is exposed. Unscrew the terminal sufficiently to allow insertion of the copper part of the wire into the hole. Turn the screw clockwise to let the jaws hold the wire firmly.
One of the advantages of using the RRBv2 board is you can run the stepper motors from a battery pack. The board has a switch-mode power circuit to provide stable power to the motors. Additionally, you can even run your RBPi from this on-board power supply. That makes the entire arrangement completely portable.
When connecting the battery pack to the RRBv2 Board, take care to observe the correct polarity of the flying leads from the battery pack. Some battery packs terminate the wires on a plug. Therefore, you must use a matching female socket adapter that has flying leads. In either case, connect the positive or red lead to the screw terminal marked Vin on the RRBv2 board. Connect the negative or black lead to the screw terminal marked as GND on the RRBv2 board. Powering on/off through a battery pack becomes simpler if there is a built-in switch.
If you have connected your RBPi to the RRBv2 board, throwing the switch to the on position will allow the RBPi to start booting. To run the stepper motor with commands from the RBPi, you will need to download the RRBv2 Python library codes. For this, you will have to connect your RBPi to the Internet.
You can use the Ethernet connection to connect your RBPi to the Internet. Alternately, you may use a suitable Wi-Fi dongle. Once online, use SSH to establish connection to the RBPi from a PC and proceed to download the RRBv2 Python library from here and install it.
To run a stepper motor, you can write some simple Python codes, following the tutorial here. For example, you will have to provide the delay between the steps, the total number of steps you want the stepper motor to move and the direction of rotation – backwards or forwards.
The delay between the steps governs the speed of rotation of the stepper motor. For example, as you make the steps larger, the motor turns more slowly to make the total number of steps.
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