audioguru2
- Apr 6, 2004
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Hi Fate,
Welcome to our forum.
I found this on the 1st page of a search for Heartbeat on Google:
http://www.web-ee.com/Schematics/HeMon/HeMon.htm
View attachment 36549
Welcome to our forum.
I found this on the 1st page of a search for Heartbeat on Google:
http://www.web-ee.com/Schematics/HeMon/HeMon.htm
View attachment 36549
But I've to work without microcontrollers and Pic... :-\ Don't know...
audioguru2
- Apr 6, 2004
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Hi Fate,
You wanted a heartbeat detector so there it is. The detector part I posted has a dual opamp but not a microcontroller nor Pic.
Now what do you want to do with it?
You wanted a heartbeat detector so there it is. The detector part I posted has a dual opamp but not a microcontroller nor Pic.
Now what do you want to do with it?
audioguru2
- Apr 6, 2004
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Hi Fate,
Look at "B" opamp, no negative feedback. At the low frequency of heartbeats, its gain must be 100,000 or more. You won't have to amplify it.
Look again at "B" opamp. It is a comparator, and it even has an adjustable threshold!
It probably already has "proper pulses" so just feed them to a counter.
This circuit is self-contained and has everything that you need. That's why I selected it for you. ;D
G
Guest
- Jan 1, 1970
- 0
how to code the oscillator display?
G
Guest
- Jan 1, 1970
- 0
yah.. but i wanna noe the lm358 op amp output type.. can u explain how it operate? wats the use of sensitivity and trigger level? thanx a lot
audioguru2
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Hi Bird,
The output type of an LM358 opamp is a complementary push-pull emitter-follower stage like most other opamps. See its schematic attached. The LM358 and its big sister, the LM324 quad opamp, is unique in that it can operate with a single supply voltage as low as 3V, and has a very low idle current. In this circuit it operates at 5V.
Opamp A operates as an ordinary AC non-inverting amplifier, with its gain adjusted by the sensitivity pot.
Opamp B operates as a comparator, with an adjustable trigger level.
I guess the sensitivity and trigger level pots allow the circuit to match the enormous difference between different fingers. Probably when a finger is cold, it has low blood-flow.
For its display, you need a counter circuit with a timebase measuring pulses per minute.
View attachment 36654
The output type of an LM358 opamp is a complementary push-pull emitter-follower stage like most other opamps. See its schematic attached. The LM358 and its big sister, the LM324 quad opamp, is unique in that it can operate with a single supply voltage as low as 3V, and has a very low idle current. In this circuit it operates at 5V.
Opamp A operates as an ordinary AC non-inverting amplifier, with its gain adjusted by the sensitivity pot.
Opamp B operates as a comparator, with an adjustable trigger level.
I guess the sensitivity and trigger level pots allow the circuit to match the enormous difference between different fingers. Probably when a finger is cold, it has low blood-flow.
For its display, you need a counter circuit with a timebase measuring pulses per minute.
View attachment 36654
Last edited by a moderator:
audioguru2
- Apr 6, 2004
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Hi Trigger,
I guess the blood flows in a finger in pulses with each heartbeat.
The blood either blocks or passes the red light from the LED with each heartbeat.
[move]Whoa! 2000 posts![/move]
I guess the blood flows in a finger in pulses with each heartbeat.
The blood either blocks or passes the red light from the LED with each heartbeat.
[move]Whoa! 2000 posts![/move]
Last edited by a moderator:
G
Guest
- Jan 1, 1970
- 0
i onli can manage to get lm358am chip.. is it ok?
audioguru2
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Hi Bird,
You didn't look it up on Google, did you?
National Semiconductor's sales information sheet says that the AM suffix is for a tiny surface-mount package. You probably want a DIL package for through holes mounting with a suffix of N.
View attachment 36656
You didn't look it up on Google, did you?
National Semiconductor's sales information sheet says that the AM suffix is for a tiny surface-mount package. You probably want a DIL package for through holes mounting with a suffix of N.
View attachment 36656
Hey Trigger...
The optical technique presented here exploits the fact that tiny subcutaneous blood vessels (capillaries) in any patch of skin (fingertip, ear lobe, etc.) furnished with a good blood supply, alternately expand and contract in time with the heartbeat. An ordinary infrared LED/phototransistor pair can sense this rhythmic change as small but detectable variations in skin contrast. That's pretty much the gist of the theory it's based on...
The optical technique presented here exploits the fact that tiny subcutaneous blood vessels (capillaries) in any patch of skin (fingertip, ear lobe, etc.) furnished with a good blood supply, alternately expand and contract in time with the heartbeat. An ordinary infrared LED/phototransistor pair can sense this rhythmic change as small but detectable variations in skin contrast. That's pretty much the gist of the theory it's based on...
audioguru2
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Hi Fate,
A 741 opamp won't work with only a 5V supply, and its output won't go anywhere near ground for a proper logic low. The LM358, MC3358, MC3458, MC33072 or MC34072 will work much better, and they are all duals to match the pinout in the article.
A 741 opamp won't work with only a 5V supply, and its output won't go anywhere near ground for a proper logic low. The LM358, MC3358, MC3458, MC33072 or MC34072 will work much better, and they are all duals to match the pinout in the article.
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