Pulse Sensor

PROJECT 1 - BPM [Beats per minute] (Simple METHOD)

Aim: Sample readings from sensor, plot on screen, plus flash HEART icon on BBC micro:bit.

Uses a basic fixed threshold method for identifying the wave that is each heart beat.

More advanced methods would calculate these thresholds based on a moving average calculation of the dynamic range of the signal (this is in the works - to be released).

On Button A: Displays BPM last & average.

On Button B: Ends program, the displays BPM last & average.

First things first - basic sampling and plotting. Instructions below - aimed at beginners and up (so skip steps you don't need).

To do this yourself :

1. Connect your BBC micro:bit to your host device (e.g. PC) via USB.
2. Connect your BBC micro:bit to the Pulsesensor.com sensor (see below).
3. Ensure you have installed the wonderful Mu editor by @ntoll (see Resources below).
4. Click "New" to create a new BBC micro:bit MicroPython project, then copy and paste the code below into your Mu editor session.
5. Click "Check" (sometimes need to press twice) and amend code as required for any warnings/errors reported.
6. Click "REPL" to enable a data connection between the BBC micro:bit and host device and which displays any prints sent through it.
7. Click "Plotter" to enable plotting of any numeric output in the REPL window
   • e.g. (50, 500) will draw 2 data lines.
   • e.g. (45,100,75) will draw 3 data lines etc.
   • Plotter allocates colours automatically to each data feed / line, i.e. 1. blue, 2. green, 3. orange, 4. purple etc.
   • Plotter dynamically scales vertical axis according to range of data currently on display.
8. Click "Flash" to transfer your MicroPython code to the BBC micro:bit which will start once loaded (or display any syntax errors).
   • If syntax errors are reported, click "Check" to identify them and fix before repeating "Flash".
   • Once the micro:bit is recognised (typically within 5-10 seconds) a file window may appear displaying the micro:bit's file contents. Simply minimise / close this to enable you to view the REPL and Plotter panels clearly.
9. Place your finger on the sensor and watch the readings appear in the REPL and Plotter panels.
   • On Button A: Displays BPM last and average on the BBC micro:bit (scrolling text).
   • On Button B: Ends the program loop, then displays BPM last and average on the BBC micro:bit (scrolling text).
10. Clicking "Plotter" a second time closes that panel - without ending the REPL session/connection.
11. Clicking "REPL" a second time closes that panel and stops the display of any data from the BBC micro:bit.
12. To run your code again, start from the step above 'Click "REPL" to enable a data connection...'.

BBC micro:bit setup - HARDWARE

SENSOR

BBC micro:bit setup - CODE

Courtesy of Online syntax highlighter (vs): http://hilite.me/

results

RESOURCES AND references

Coding

• Mu Beta 15, March 2018 code editor with live data Plotter feature to graph live REPL data
• http://microbit-micropython.readthedocs.io/en/latest/index.html
• https://github.com/WorldFamousElectronics/PulseSensorPlayground
• Getting Started Project - Arduino sketch with notes
• More Advanced - using Inter Beat Interval (IBI) method of finding heart beat
• Building a MicroPython heart rate monitor | Finding the beat in HR sensor data (using an Arduino)

Pulsesensor.com

• https://pulsesensor.com/pages/getting-advanced
• https://pulsesensor.com/products/pulse-sensor-amped