Lesson 1 - About the PiArm Shield

PiArm shield is a source of connection between your Pi and the PiArm. It provides you with options to connect the motors as well as many other sensors in order to add more functionalities to your PiArm.

PiArm shield

Features

ON/OFF switch
6 motor connectors
AC supply terminal
The PWR LED
Dual modes of connection for communicating with the Raspberry Pi
2 IR sensor, 1 Ultrasonic sensor
'Low-Power' indicator
A single power source for the robot and the Raspberry Pi

On the board

On board shield

Switch:On the shield an ON/OFF switch is there to boot the Shield.
Motor Connector: There are 6 servo motors that are connected together for the movement of the Arm. To connect these motors to the Pi 6 JST connectors are embedded on the board for easy connection. There are two types JST type 1 and Type 2. Connect the motor wire to Type 1.
Battery Connector: It provides supply to the shield as well as the Raspberry Pi. Pi works on 5V and also the sensors like IR, ultrasonic operates on less than 5V but the motors operate on voltage greater than 6V so to drive motors you require an external power supply.
Note: Before connecting battery, make sure that the power is OFF. On the board, terminals (i.e + and -) are mentioned so connect the wire of the battery to the terminal according to the polarity of the battery.
Power LED: An LED is also embedded in the board which tells the state whether the shield is getting power or not.
Sensor Headers: To make PiArm smart there are IR and Ultrasonic sensors. To connect these sensors there are IR as well as Ultrasonic sensor header on the board for easy connection.
- IR sensor: To connect IR on the board, connect the pins of the IR sensor as mentioned on the board.
- Ultrasonic sensor: The board also has the headers for connecting the ultrasonic sensor. The pins are mentioned on the board, so connect accordingly.
Low voltage indicator: You never run out of power and your shield doesn't crash there is an indicator on the board to indicate insufficient power supply. A buzzer will beep to indicate the low voltage.
DC-DC converter:It basically regulates the voltage inside the board. The parts connected to the board work on different voltages, to supply desired voltage to the components voltage regulator circuit are used.

When connecting an external power supply with voltage 6V-12V to the terminal the Raspberry Pi also gets power up because of this circuit. It converts the voltage to 5V, 3.3V and 6V to run the desired components.
There are headers on the board of 3.3V and 5V also.
Power USB for LCD: The shield also has the feature to attach an LCD on the Pi or you can also power the LCD from Pi USB ports also.
Serial communication USB: It is used to connect the Shield and the Raspberry Pi. Using USB you can establish a communication serially between the shield and the PiArm.

For serial communication, there are two ways of connecting the PiArm with the shield. Refer below for more information.

Connecting PiArm with Raspberry Pi

To connect PiArm and Raspberry Pi we require a device that can communicate with both the devices. To fulfil it Servo Shield was designed. It allows two-way communication with the Raspberry Pi Board, using the USB or through the GPIO.

You can connect the shield through a couple of options:

USB: On the board, there is a USB connector. Using the USB port you can connect the Shield and PiArm via USB cable.
Note: If connecting via USB cable then make sure you give supply independently to each device.
GPIO: On the backside of the shield, there is a female GPIO header. To attach the Servo shield to the Raspberry Pi, simply stack the shield onto the Raspberry Pi. Make sure that all of the pins are correctly seated and the Shield over-lays the Raspberry Pi.

It has the power to provide a single power source to the Raspberry Pi and the PiArm both.

Note: If connecting via GPIO then one power supply of voltage 6V-12V (connected to the battery terminal) is sufficient to power up both the shield and the Raspberry Pi, no need to supply power to Pi separately.

Once the connection is done, now connect the motor on the shield via wires. Connect all motors serially and then the last wire of the motor on the board.