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Pulse sensor problem

Posted: Mon Mar 02, 2015 4:09 am
by prabu_cc
Hi Paul,

I recently bought the pulse sensor from MD and i am trying to hook it up with Arduino Leonardo board. I am using the example code in the following link: ... lights-on/

I connected the scl/sda pins(top right) on the arduino to the scl/sda pins on the sensor. I understand the arduino is 5v and the sensor is 3.3v. When I run the program,I get the value "196605" on my serial port.

When I measure the voltages, the scl pin has 4.9v but the sda has 0.05v. I was expecting 5v on the sda though. Not sure what is going wrong. is it because of the mismatch between arduino(5v) and sensor(3.3v)and 10k series resistor missing??? Also, do i need to make any changes in the pins since i am using arduino instead of jeenode boards?? The scl/sda pins are connected to pins 18/19 on the atmega chip.

I ran a simple i2c_scanner program to check if my i2c connectoins are ok??...the i2c_scanner program can detect the pulse sensor with the slave address of 5A, which is correct.

So one program works fine and the other program is not working, with the same connections.

Please share your thoughts and thank you for your time in advance.

Use a couple of 10K series connectors to connect the SCL and SDA pins on the sensor to the 'duino pins listed in the chart below. If you are using a JeeNode or other Jee board, just plug the sensor into a port - or use a six-pin extension cable.
Port SCL 'duino pin SDA 'duino pin
1 4 14 (A0)
2 5 15 (A1)
3 6 16 (A2)
4 7 17 (A3)

Re: Pulse sensor problem

Posted: Sat Mar 07, 2015 11:09 am
by paul
We went over the library and revised it for Leonardo. Also due to work with Mega2560 chips shortly. Please download the latest version of the library from Github and you shouldn't have any trouble hooking it up.

Good luck and let us know if you have further problems,


Re: Pulse sensor problem

Posted: Fri Sep 18, 2015 12:52 pm
by internetizen
Hi Paul,
I am using Mega2560. Do you think you can update your library ASAP?
Thanks a lot!

Re: Pulse sensor problem

Posted: Fri Sep 18, 2015 4:32 pm
by internetizen
Hi Paul,

I am using Mega2560. Do you think you can update your library for Mega2560 ASAP?

Thanks a lot!

Re: Pulse sensor problem

Posted: Tue Feb 09, 2016 11:41 pm
by wintrmute
Hi Prabu,
When using i2c, you're supposed to have 2-5k pull-up resisters on the i2c (SDA/SCL) lines. (ie. Connected to a 3v3 source)

I saw something in the notes on Github mentioning putting 10k resisters *in series* with the lines, but nothing about the pull-ups.. Not sure if that was an omission or assumed knowledge (that I certainly didn't have!).

I've started working on a fork of the SI114 library, to make it use the standard Arduino i2c library, rather than Paul's inline PortI2C code. I think this should make the code compatible with a wider range of devices, since the Wire library already works on everything.

My work so far is here: ... re_Library


Pulse sensor problem

Posted: Sat Sep 09, 2017 6:47 pm
by Aaronhycle
Hello forum,

I recently received a respiration sensor bought on the BITalino store which I would like to plug into a Board Kit.
I was first thinking about simply cutting the RJ22 plug at the end of the sensors cable and connect it in some way to the board, but Im not sure if this is the best idea, and anyway I wouldnt know how to connect these 4 wires ...

What are the options for accomplishing this ?
Is there a preferred way to do it ?

Thank you in advance for your answers.


Re: Pulse sensor problem

Posted: Sat Oct 14, 2017 3:18 pm
by paul
We can't really support other people's hardware, especially without schematics and datasheets.

My guess is that the sensor is just an analog output - it may be just a raw piezo element which you would need to condition with an op amp. From the discussion I read online that's exactly the case. They do have their own forum.