Signals oscillate in diferent Thresholds about pulsesensor_pulse_transit_time HOT 7 OPEN

I can't say what changes need to be made, as I have no idea what the parts they used to make their knockoff. Sorry.

As for the LED, we use a green LED because the sensor we use is most sensitive at that wavelength. IR would not be effective if it were our hardware.

Thanks for the links to the papers! They look very interesting indeed.

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@VladiLuzJr
Thanks for using Pulse Sensor!
Your signal does look small.
I don't think you will have signal problems because of the sensors being too close.
If you are using Arduino Uno, you should definitely use the interrupts. They make the result very accurate.
I have not used this code base in a little while.
I will try to replicate your problem and see if I can make it work.

Also, can you verify your hardware? Send a picture of your setup?

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Greetings @biomurph!

Thanks for communicating with us and being available, we acknowledge your dedication...
Firstly we would like to congratulate you for your hard work in the pulse sensor project, we are very happy to collaborate with you.

In the following link you can take a look in the video we have recorded, in order for you to understand the hardware configuration(I am sorry for the cable management....)
https://drive.google.com/file/d/1gY98lt8Hd64yu2MZn41rZvPAbFaBdhiK/view?usp=sharing

This is how we test the software, for PTT acquisition:

Here follows the Arduino an protoboard pinout:

Pulse Sensor 1(Analog pin0)

Pulse Sensor 1 Front:

Pulse Sensor 1 Back:

Pulse Sensor 2(Analog pin1)

Pulse Sensor 2 Front:

Pulse Sensor 2 Back:

If there is any doubt, please fell free to ask me...
Sincerely, Vladimir

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@VladiLuzJr thank you for sending the pictures. They make everything very clear.
First, you are not using the Pulse Sensors that we make. Those you have are knockoffs. I can't troubleshoot your hardware because I don't know what is on those boards. Please support the original makers of open source hardware and purchase legitimate products. You can guy on our site, www.pilsesenslor.com, or Adafruit, ot SparkFun, also Mouser and Digikey carry. Also, SparkFun bundles our PulseSensor in a kit they ship to brick-and-morter stores around the world. Check their 'distributors' page and call around if you have trouble ordering.

Regarding the PTT measurement, I would like to know if you have any study or white paper that you are following to put the two sensors so close together? They seem to be too close in proximity to get a valid or useful PTT. At the distance you have, it may require a rather high sample rate to gather anything useful. I usually see PTT placement in earlobe and fingertip, or other far away sites. This makes the difference easier to measure, as well as being able to tell when there are changes due to vasoconstriction. Much easier when further away.

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@biomurph , thanks for your attention!

Sorry I have bought those knockoffs... guess the COVID-19 crisis have effected the Brazilian currency, in a way two Pulse Sensor would cost R$500.00 with shipping in SparkFun.

Do you think I could by me some of these real IR LEDs and re-attach them as in thins link:
https://makezine.com/2012/02/17/reel-crime-the-pulse-sensor-counterfeit-leds-story/

or should I manage to achieve some real ones for myself???

In regard to the Pulse Transit Distance, I will link in some paper in witch the distance of (Wrist - finger or even

closer) were used. We proposed ourselves(by using different microcontroller, such as a STM32 which has higher clock settings), if it was possible to built-in the "local-PWV" measurement in an oximeter device.

Happy to share our research with you...
Furthermore through the end of the year I will link our published paper if I may!

28mm apart IR Rx for local PWV:
Carotid_Single_Source_DuallPPG_PWV.pdf

Wrist_finger PPG:
Wrist_FingerPPG_PWV.pdf

Wrist-finger for SPWV:
nam2013.pdf

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I meant those brighter green LEDs as referred in the blog post, lol.

Although I understand it wouldn't be possible to know the components used... I have an Oscilloscope in hands, maybe I'll try to hard dig what is creating this difference in threshold. In the mean time I am looking forward to buy myself some real pulse sensors....

Thanks for being supportive!
As soon as I have more news I will keep in touch

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Please do let me know what you discover. In our design, the raw PPG from the sensor can be found on the left side of the capacitor just above the green wire in your hardware photo.

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