A very interesting project to build in the student of grade 7/8 a Stirling engine for watering your school garden.
All this is supported with many images, PDF files and an easily understandable theory.
An ideal project for more school gardens and a nice resource for personal knowledge base.
… 12 students of the Montessori High School have done something very special. They want to water their school garden with innovative technology. In cooperation with the Stirling Institute of Technology a non-profit company from Potsdam will to be built a solar low temperature Stirling engine. The invention is based on the patent of the Institute with the no. 100 16 707.
The following images are showing my circuit diagram and the test setup.
The first test worked flawlessly both in the direction to the Pi and in the direction to AVR microcontroller.
The third picture shows the circuit diagram used and the fourth image the development on breadboard. Now I can connect my test board and the Pi over normal jumper cable to have hanging around without various additional boards.
The Raspberry Pi is equipped with many interfaces.
And the possibilities can rise more than exponentially by using of the USB port.
But to communicate with AVR microcontrollers is the best suited way by using a serial interface.
Of course, the Raspberry Pi A has a serial interface, but unfortunately merely as pins on the GPIO connector.
The required pins, could be connected theoretically directly to the microcontroller eg. ATMega8.
But that would require that the microcontroller operates at 3.3 volts.
My Pollin evaluation board works with 5 volts, but is made with a complete RS232 interface for communication with PC or other equipment.
The easiest way would it be, when the Pi would have an RS232 interface like a PC with the same connectors and signal levels.
By Googling I’ve found the website Serial Port Add On.
The described Serial Port to TTL Digital Converter Module there, I’ve bought at Ebay.
GPIO Header Pins
1= 3.3V, 9= GND, 8= TX, 10= RX
The jumper cables to connect to the Raspberry Pi were included in the delivery.
I’ve connected the module with the Pi, as shown in the picture below.
To get the serial interface up and running, are some changes in/etc/inittab and /boot/cmdline.txt necessary.
For that I’ve written a little perl script. Surely it is possible to use programs like minicom, but I dont wanted to spend the time to familiarize myself with a new tool.
The script was written faster and from my perspective it’s much more flexible for further use and for experiments.