Safe & Sound T-Shirt for Monitoring Elderly and Physically Challenged Patients #6 : Breathe and Heat

11 Apr 2017

Hi guys,

Have been busy lately, so here is this week's post. Sensing Breathe and Temperature.

I came across this conductive elastic chord which changes its resistance as it is stretched, so decided to use it as a respiratory sensor. 1m of the chord has a resistance about 10k and increases as elongated.

The setup:

The chord is without any insulation so I had to tape them on my t-shirt to avoid shorts.

Just a analog read program with increased delay and the Serial Plotter gave:

A expected output but too much of noise, tired replacing the jumpers, isolated power supply. Any suggestions or solutions are welcomed.

The temperature sensor is actually a MAX30205.

Its actually a clinical grade I2C sensor, you can find the library and Example code here.

Connection

3V3 -----> 3V3

GND ----> GND

SCL ----> SCL

SDA ----> SDA

I just Increased the delay to 1000ms

Cheers

Top Comments

sakthi.1260 over 8 years ago

Jan Cumps DAB dougw mcb1 thanks guys tried all those stuffs still its picking up noise, haven't tried the Low pass filter, will see if it works
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mcb1 over 8 years ago

First thing I'd try is swap the conductive string and the 10k resistor so that you have the string between the pin and ground.

Mark
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dougw over 8 years ago
It is always good to find the source of the noise to see if it can be eliminated at the source.
- move the system closer to anything that might be supplying the noise to see where it gets worse
A second approach is to shield your system from unwanted noise
- try shielding various parts of your system by enclosing them in a Faraday metal cage - like aluminum foil
- try shielding the sensor with copper braid
- try grounding the shields
If these are not feasible the noise looks to be short duration spikes that can easily be filtered out by a simple low-pass filter.

The sensor looks interesting - what is the manufacturer and part number?
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DAB over 8 years ago

I agree with Jan.

I think you might be picking up some EM from lights or other electronics.

I would suggest wrapping the area with aluminum tape or a flexible conductive screening material and grounding that material.

That way, you should isolate your sensor to just signals on the body.

If they still persist, then you will probably need to add some analog or digital filtering.

DAB
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Jan Cumps over 8 years ago

That noise must come from outside and is picked up by the device or the jumper cables. Are you in the neighbourhood of led lights, a switching power supply, a tv, computer, a dimmer?
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