Detecting heart rate using an Arduino 101

I’ve finished an Arduino Pulse Sensor library based on Joel Murphy’s and Yury Gitman’s Pulse Sensor Amped Sketch. The library and example code running on an Arduino 101 communicates with Joel’s and Yury’s Processing Visualizer that graphs the pulse waveform.

The cool thing about this library and example code is that it runs on all sorts of Arduino compatibles without using ARM-specific Timer Interrupt setup code. So it runs on the Intel-based Arduino 101 “out of the box” as it were.

The code is at https://github.com/bneedhamia/PulseSensorBPM, and I’ve put a demo video on You Tube. Party On, Arduino 101!

Arduino 101 detecting pulse rate
Arduino 101 detecting pulse rate

The library can be used either with or without Interrupts.  The library example PulseLooper in github works on Arduino 101 and Arduino Uno, without using interrupts; the example PulseInterrupter uses ARM-specific interrupts and so runs only on ARM-based Arduinos such as the Uno.

Mounted the Lunar Clock opto-interrupter

In my last post about the Lunar Clock I described the opto-interrupter that will detect the slot in the lunar images disk. At that time I wasn’t sure how to mount the opto-interrupter to the strip that holds the stepper motor that turns the lunar images disk.

Recently I bought an angle bracket to mount the opto-interrupter.  Although it’s the smallest bracket I could find, it’s still pretty big, with holes that are far too large for my use.

the angle bracket holes are too large
the angle bracket holes are too large

So I used a hacksaw to cut one side of the angle bracket down to a size I could use.

hacksawing the angle bracket, using a board as a guide
hacksawing the angle bracket, using a board as a guide

Next I drilled new, smaller mounting holes the size of the short bolts I have used in the clock.

drilling the base mounting holes
drilling the base mounting holes
drilling the size hole that will connect to the opto-interrupter
drilling the size hole that will connect to the opto-interrupter

I then bolted the opto-interrupter to the bar of wood that holds the stepper motor.

Opto-interrupter fastened to the clock
Opto-interrupter fastened to the clock

Now it’s time to design the artwork that will be on the front of the clock.