Detecting heart rate and breath rates

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hiv0ltage	Posted: 2 Dec 2023, 07:12 AM
Member Posts: 2 Joined: 2-December 23	I have been looking for a proper sensor to detect heart rate for a horse. They have ones that you can buy but they are terrible for the application I need them for. I figured that a horse has a large neck and the sensor can be placed there and attached using a neck sweat (the ones that are wrapped around the horses neck and look like a scarf). The issue is the fur. in humans our skin is easily accessible but on horses its not. I do not want to shave my horse just to add a sensor there. I also need the senor to be safe and not irritate. Horses are prone to rub and could either damage the sensor or its skin. The breath rate is similar and can be added to the throat area where the heart rate sensor is. The goal is to monitor the horse even if its lying down. The expensive ones goes on the legs and can be easily knocked off or shifted plus they don't measure the horses breathing. Once I can get a decent sensors I am pretty cleaver about the code. Any ideas welcome. And yes I own a horse. ;) -------------
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mit	Posted: 4 Dec 2023, 01:51 PM
yeah whatever Admin Posts: 566 Joined: 4-May 16	This has to be one of the most unusual requests posted here. As far as I know, the sensors on smart watches are actually quite bad at what they do, most of them are very inaccurate, and usually sampled too infrequently for anything but casual interpretation. I have seen some interesting projects that use a webcam to monitor heartrate by applying DSP autocorrelation techniques to the video footage. It sounds implausible, but it apparently works. But it depends on the extremely subtle variations in skin tone, which would again be hidden under the fur on a horse. There is something appealing about simply having a camera in the stable and using computers to extract heartrate and breath info from the footage. -------------
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fogh1	Posted: 9 Dec 2023, 04:20 AM
Member Posts: 5 Joined: 9-August 22	Might just be able to strap an accelerometer in a strategic location and find the periodic signal from the heart beating. I like to think that my Apple Watch is at least decent at heart rate detection. Breathing rate probably not. -------------
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hiv0ltage	Posted: 9 Dec 2023, 11:31 PM
Member Posts: 2 Joined: 2-December 23	I know it is unusual but I was hopeing to find something that would work. Even if its not perfect. Just has to be able to detect if the horse is agitated or not. Using a video would require a lot of signal processing and that is beyond my capability atm. -------------
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mit	Posted: 24 Dec 2023, 10:01 PM
yeah whatever Admin Posts: 566 Joined: 4-May 16	Forwarding the following message: QUOTE Hello - I work in cardiology, so thought I'd weigh in. There are two common ways to transduce heart rates (and a few other more exotic ones). Most common is an infrared diode that sees changes in the IR reflectivity caused by pulses of blood flowing by. These are in the backs of smart watches and the common fingertip pulse oximeters. The other is to measure the surface voltage produced by the heart beating - an EKG signal. It corresponds to changes in the amount of sodium on the outside of the heart muscle cells with contraction. For your application, the second might be easiest. It would require less pressure on the neck. A collar worn low done might do it. The electrodes should be to be as far apart as possible and close to the withers. Most parts of a horse's skin might be too thick and pigmented to pass the IR type signal. The circuits are usually one or two low noise op-amps, with careful filtering. Circuits are widely available (look for "EKG" or "ECG"), and I believe someone (Maxim?) made an optimized chip for the commercial EKG machines. Hope that helps! Ralf B. -------------
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