One of the most interesting thing about being a maker is you never get tool-stranded, with the right components, makers tend to have the ability to build makeshift tools on the go. Today, we will take a look on how to build a cheap version of one of the most important tools for any electronics engineer or maker; The Oscilloscope.
The Oscilloscope is a test instrument used for the visualization and observation of varying signal voltages, usually as a two-dimensional plot with one or more signals plotted against time. They are used in the design and debugging of electronic devices to view and compare waveforms, determine voltage levels, frequency, noise and other parameters of signals applied at its input as it changes with time. This makes Oscilloscopes a very important tool on the desk of an electronics engineer or maker. However, Oscilloscopes are quite expensive, they cost between $45 – $100 for a small oscilloscope and above $300 for advanced oscilloscopes, which puts them beyond the reach of basic users. But what if we could create something cheaper, compact, and highly functional using the components familiar to makers? That is the question that led to today’s tutorial.
For today’s tutorial, we will build the HS101 Oscilloscope. The HS101 Oscilloscope setup comprises of the HS101 portable and compact DIY oscilloscope, connected to an Android-based mobile phone or tablet running the HScope app. The oscilloscope is based on the STM32F103microcontroller which has 2 fast, 12-bits ADC and it samples the signal to be examined (after it has passed condition elements, like a network of resistors capacitors and diodes) on board.
Some of the features of the HS101 includes;
- Single Channel Oscilloscope
- 12 Bits ADC resolution
- 0-20v Input voltage range
- Sampling rates between 3KS/s – 1800KS/s
- Bandwidth 200kHz
- Up to 100KSa/s continuous acquisition
- Input noise depends on the sampling rate. < 15mV for sampling rate <=100KSa/s
The oscilloscope can be used in standard situations for tasks like DC measurements while also being useful for long period voltage logging and basic automobile checkups like;
- Battery level logging
- Battery Ignition Off Draw (IOD) data logging (with C650-like amp clamp or a DIY tool)
- Alternator AC ripple level (example here)
- In-Cylinder Compression Test (with 100 PSIG pressure sensor, example here
The following components are required to build this project;
- STM32F103C8 Blue Pill
- USB to TTL Cable
- 1N4007 (2)
- 10K Resistor
- 2k Resistor
- 470pF Capacitor
- USB OTG Cable (Micro USB to Micro USB / USB Type-C to Micro USB)
- Perforated PCB Boards (anything with 6 to 7 holes should do it).
- 6 Pin single row female 2.54mm pin header (2)
- Probe and BNC Connector (plain wires or a 3.5mm audio jack can be also be used)
You could also decide to make a Printed circuit board for this project. The BOM, Schematics and the PCB design are attached under the download section of this tutorial.
The schematics for this project is unbelievably easy. The Input module comprising of the resistors, capacitors, and diodes is built/soldered on the perforated (proto) board and then mounted on the STM Blue Phil board using the female headers which plug directly into the Blue Phil. This makes the design modular and compact. Connect the components on the protoboard as shown in the schematics below.
After soldering the parts, plug the input module on the STM Blue pill as shown in the image below.