#### alexkinglp

Joined Nov 17, 2023
1
Hello, I am pretty much new to Digital Circuits, I am having difficultly design this Heart Rate Alert System I got as a project. I am pretty much confused I was able to create like a simple alarm system that accepts the input of 3 sensors, if 2 of the 3 sensors are on it will trigger alarm. After which I was given this project to complete is it the same thing as the simple alarm system I did before? I am feeling very lost, I tried creating a truth table but it always look incorrect for some reason.

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#### WBahn

Joined Mar 31, 2012
29,865
The specs are incredibly vague. It says that it will trigger on ANY change in heart rate that does not return to its prior state within 30 seconds.

What sets the reference heart rate?

If the reference heart rate is 62.39 bpm and it goes up to 62.51 bpm, does that sound an alarm if it has only come back down to 62.42 bpm at the end of 30 seconds?

Almost anything a person does is going to change their heart rate. Watching TV and get up to go get a glass of water -- change in heart rate that lasts more than 30 seconds? Eat lunch? Change in heart rate that's going to last for more than 30 seconds? Lay down to take a nap? Change in heart rate that lasts for more than 30 seconds.

#### joeyd999

Joined Jun 6, 2011
5,171
The specs are incredibly vague. It says that it will trigger on ANY change in heart rate that does not return to its prior state within 30 seconds.

What sets the reference heart rate?

If the reference heart rate is 62.39 bpm and it goes up to 62.51 bpm, does that sound an alarm if it has only come back down to 62.42 bpm at the end of 30 seconds?

Almost anything a person does is going to change their heart rate. Watching TV and get up to go get a glass of water -- change in heart rate that lasts more than 30 seconds? Eat lunch? Change in heart rate that's going to last for more than 30 seconds? Lay down to take a nap? Change in heart rate that lasts for more than 30 seconds.
In fact, a monotonically steady heartbeat is considered a sign of stress.

#### WBahn

Joined Mar 31, 2012
29,865
In fact, a monotonically steady heartbeat is considered a sign of stress.
Never heard of that -- and wasn't able to track down anything on it (in a couple minutes).

Do you have any references for it -- would be interesting to look into.

#### Ya’akov

Joined Jan 27, 2019
8,973
Never heard of that -- and wasn't able to track down anything on it (in a couple minutes).

Do you have any references for it -- would be interesting to look into.
I think @joeyd999 is referring to HRV (Heart Rate Variability) which focuses on IBI (Inter-Beat Interval). It’s not concerned with the globally averaged rate but the time between beats.

I think you’ll find plenty of material on HRV.