Tag Archives: PI-Plate

Making a PiPlateBot with the Raspberry Pi

Turtle robots of the yesteryears had always fascinated Robert Doerr and he decided to create one with the popular single board computer, the raspberry Pi or RBPi. He hid all components of the robot inside the plate case, and decided to call his robot PiPlateBot.

Robert Doerr is the owner of Robot Workshop, and a dedicated robot builder. He used the Bud Pi Plate case, as this was strikingly similar to the turtle-style robots computer science students used earlier.

The Pi Plate has a circular design. Twisting off the top allows easy access to the space within that can house additional components. That led Robert try to fit an RBPi inside, along with the other parts required to build a moving robot. According to Robert, the PiPlateBot is the only robot that runs on an RBPi and uses an off the shelf RBPi case. Robert claims he is using as many RBPi-type products as possible for the construction.

To get everything to fit, Robert had to cut two rectangular holes in the Pl Plate enclosure base. Then he glued servos to the bottom and clipped the RBPi and RoboPi boards on the top. On the boards, he placed a BZO power bank to work as a battery. To enable communicating wirelessly with the RBPi, Robert uses a USB Wi-Fi adaptor. This allows him to SSH directly into the RBPi.

The RoboPi is an impressive motor controller, and the most powerful one for the RBPi. Using an eight-core 32-bit Parallax Propeller RISC micro-controller at 100 MHz, it allows offloading hard real time IO from the Linux OS running on the RBPi, thereby giving timing with greater precision to projects. The RoboPi will work with any RBPi model.

Each core on the RISC controller works at 25 MIPS, with each instruction taking only four clock cycles to complete. The RoboPi has three ten-pin IO module expansion connectors and they provide 24 servo-compatible headers. Some of these connectors use jumper selectable power from the internal 5 VDC or the external servo power supply for powering the sensors.

The user can connect servos to screw terminals that provide external power. There are eight headers for setting up an eight channel 0-5 V analog to digital converter. The user has a choice of using MCP3008 for 10-bit AD conversion or MCP3208 for 12-bit AD conversion.

Therefore, while the RBPi does the high-level thinking, the Parallax Propeller chip on the RoboPi board handles all the IO controlling and the real-time tasks. As the RoboPi controller has both C and Python libraries, Robert plans to write a Logo Interpreter to make the PiPlateBot use Logo to emulate the early turtle robots.

As the PiPlateBot has only two servos controlling its two wheels, the robot actually wobbles when operated. Robert had to use furniture gliders to prevent this. He attached them to the front and rear of the PiPlateBot. A sonar sensor fitted on the PiPlateBot allows it to sense its surroundings.

Building a robot is the fun way of learning to use the RBPi, and a great way to learn programming on the SBC.

Stackable Pi-Plates for the Raspberry Pi

If you are faced with a paucity of projects for your Raspberry Pi or RBPi, the tiny, credit card sized single board computer, you should get the circuit boards from Pi-Plates and connect your RBPi to the outside world. Pi-Plates offer a family of stackable, add-on boards that provide your SBC with a robust set of features at a minimal cost.

Pi-Plates design their circuit boards to be economical with the GPIO pins they use from the RBPi header. For example, when using the DAQCplate board, it uses only two dedicated GPIO pins. However, you can stack eight of these Pi-Plates to get 64 digital inputs, 56 open-collector outputs, 64 analog inputs and 16 analog outputs. Whether you are an experimenter, a hobbyist or a professional, Pi-Plates have designed these boards to be useful for all. Additionally, these are mechanically and electrically compatible with all revisions of the RBPi. That includes versions A, B, A+, B+ and the new version 2.

At present, Pi-Plates offer four products. The flagship product is the DAQCplate board that has ADCs or Analog to Digital Converters, DACs or Digital to Analog Converters and expanded digital IO. MOTORplate is a new product for controlling motors and you can use it to drive two stepper motors or four DC motors, while its onboard software can handle all drive logic including acceleration profiles. If you want to add custom hardware on your Pi-Plate stack, you can use the PROTOplate board.

When stacking Pi-Plates, you will need a secure structure and this is provided by the BASEplate mounting system. All hardware necessary for mounting to the BASEplate is already available with each Pi-Plate board. Pi-Plate also offers two great kits.

The DAQC kit comprises two BASEplates and one DAQCplate boards for the price of a single unit. This makes a great beginning for those starting with the DAQCplate for the first time.

For those starting with a MOTORCplate, the MOTOR Kit may be very useful. This kit comprises one MOTORplate and two BASEplate boards for the price of a single unit.

For example, the DAQCplate is a data acquisition and control board. Its digital output section has a connector that provides seven open-collector outputs and a pair of 5VDC outputs that you can use for driving loads. You can protect these with a flyback diode connected to the terminals.

You can use these outputs to drive incandescent automotive light bulbs, ultrasonic rangefinders, resistive heating elements, unipolar stepper motors, buzzers, solenoids, relays, DC motors or LED strings. Green LEDs connected to each digital output light up to indicate a high on the output. To light up these LEDs, you do not require connecting anything to these outputs. At the same time, these LEDs will not affect anything that you connect to these outputs.

Darlington pair transistors drive the seven open-collector digital outputs. They can sink a maximum of 350mA and handle a maximum load voltage of 12VDC. With a load voltage of 200mA, the on voltage is typically 1.1V. When using inductive loads such as solenoids or relays, you must connect the high side power supply to the flyback protection terminal.