Pulse Sensor saturates

Other Hardware Sensors
1

Hi All,

I'm currently testing the Pulse Sensor and it often saturates cutting my systolic peaks.

I have observed the same behavior with Arduino UNO, nRF52840DK and Bitalino boards. As a side not I power the sensor with 3V among the allowed voltages (3V and 5V).

Has anyone experienced the same issue and knows how to fix it?

Thank you!

2

Sounds like a good and fun project. I would suggest you post a schematic, not a frizzy thing so we can get an idea of what you are building. I did not find the specifications on the sensor either.

3

I'm guessing (in the absence of further information) that the pulse sensor is just intended to sense pulse rate, not to be a professional qualiy diagnostic tool. Its described as a heart RATE sensor.
You could try it on different areas as the skin thickness etc would affect the signal.

4

Thank you @gilshultz and @johnerrington for your input.

gilshultz:
Sounds like a good and fun project. I would suggest you post a schematic, not a frizzy thing so we can get an idea of what you are building. I did not find the specifications on the sensor either.

Here you can find the specifications of the Pulse Sensor. The sensor comes with:

  • RED wire = +3V to +5V
  • BLACK wire = GND
  • PURPLE wire = Signal

My schematics are very easy and I can simply describe them here:

  • Arduino UNO: RED to +3V or +5V; BLACK to GND and PURPLE to A0
  • nRF52840DK: RED to VDD; BLACK to GND and PURPLE to P0.02

johnerrington:
I'm guessing (in the absence of further information) that the pulse sensor is just intended to sense pulse rate, not to be a professional qualiy diagnostic tool. Its described as a heart RATE sensor.
You could try it on different areas as the skin thickness etc would affect the signal.

I am not using this sensor just to detect the pulse rate, but I am instead looking for patterns in the whole signal. For this reason each time-frame of the signal is important to me and these "cuts" of the systolic peaks are giving me problems. The "cuts" don't happen always and don't happen on every area of the skin, but I cannot yet understand what is causing it. Any ideas?
Thank you!

5

The pulse rate sensor has a high pass filter which severely modifies the photodetector output waveform, and a fixed 12K load resistor on the photodetector (data sheet here) which might be saturating. The saturation would depend on the ambient light level and the position of the detector on your body.

So, you really have no idea what the waveform actually represents. What do you want to see?

6

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