The oscilloscope is on the wish list of anyone starting out with electronics. Your author used to tell his students that it was your eyes, making electricity visible. Unfortunately, they are quite expensive: from a few hundred pounds to up to £5000 and beyond. However, by using an Arduino and some software on the Raspberry Pi, you can make a passable beginner’s oscilloscope.
Last September, in The MagPi #61, there was an article outlining the way the Raspberry Pi and the Arduino could be used together. We at the Bakery have been doing this for some time: we first had a major project in the Raspberry Pi Projects books by Andrew Robinson and Mike Cook. The big advantage of the Arduino from a signal processing point of view is that there is minimal interruption from the operating system and you can gather data at a constant uninterrupted rate. This is just what we need for making an oscilloscope. The idea is that the Arduino gathers a whole heap of voltage samples as fast as it can and stores it in memory. It then transfers that memory to the Raspberry Pi, again as fast as possible. The Pi plots the data and displays it, then the software allows measurements to be made on the samples.
So you can measure the time and voltage difference, known as a delta, between any two points on the samples. You can even display the frequency that the ‘time delta’ corresponds to by taking its reciprocal. These are features found in expensive oscilloscopes. We have also built in a trigger function; this is to synchronise the onset of the rapid data gathering with the occurrence of a positive transition on the input signal through a specified voltage. The result is that regular waveforms can look stable on the display.
Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, or even use Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for MakeCode, CircuitPython, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.