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Building from scratch

A project log for Oximeter do it yourself

In this period of isolation, I'm trying to build an oximeter with parts already in house. An oximeter is made by two leds and a photodiode.

giulio-ponsGiulio Pons 06/07/2020 at 16:120 Comments

I've tried to build the oximeter from scratch, with a LTR-301 photo transistor and it doesn't work as expected.

The problem is the LTR-301 spectral response which is quite narrow around 940nm. So it doesn't receive the red light!

To build from scratch (without hacking a KY-039) we need to use a wide range photodiode, such as the LPT 80A which can receive both red (600 nm) and infrared (940 nm) light.

Maybe finding a phototransistor with Srel (Relative Spectral Sensitivity) value around 600nm very similar to the 940nm (in this one it's 50%) is also better:

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