Maarten's RPM (Revolutions Per Pinute) meter.
This project describes how to make a RPM (revolutions per minute) meter. It uses an ESP8266, a 4 element 8x8 LED matrix and a line tracking sensor. Jan Ridders of Jan Ridders Modelbouw requested this project. He needs to measure the speed of his Stirling, steam or combustion engines. The ESP8266 was chosen because it is easy, cheap and known to Maarten; this project does not (yet?) use the WiFi capabilities of the ESP8266.
See YouTube for a demo of the project.
The following components are used in the project, total cost below $10.
- Line tracking sensor An infra-red emitter and detector - sub $1 (half priced alternative).
- 4 element 8x8 LED matrix A 4-in-one MAX7219 based 8x8 Dot Matrix Module - sub $4 (alternative).
- NodeMCU/ESP8266 NodeMCU V3: ESP8266, 32M flash, CH340G (USB-serial) - sub $4 (half priced alternative).
For wiring information (power, schematics, photos) refer to the wiring directory.
The software (firmware inside the ESP8266) is available as binary, and can be flashed relatively easy. Another option is to install the development environment (compiler) and work from the source; refer to the arduino directory.
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