Please help urgent : heart beat monitor

[THEPUNISHER]

Hai,

Iam doing a project on Heart beat monitor.Nothing much just a project that produces sound in a speaker from the heart beat pulse..The project is without microcontrolelrs

But i wish to moddiify the project by also adding a additional counter along eith it.i.e a counter to count the no of heart beats per minute[it shud store and show values beat in a minute not more than tht]and display it in a seven segment display.

Can you tell me what i am supposed to do?

thanks in advance

this is my circuit
**broken link removed**

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[Nigel Goodwin]

I should try that 'as is' first and see if it works, I'm amazed at the date on the bottom (2001) - it looks more 1960's than 21st century.

I'm also horrified by the preset in the transistor collector.

 

[audioguru]

It is a horrible old fashioned circuit like most circuits from that website in India.
The first and second transistors are biased like we were taught "never to do like that" with a single resistor to the positive supply voltage. Transistors biased like that are thermometers instead of amplifiers.

 

[THEPUNISHER]

Hey

thanks everyone for their valuable reply.
Hey can someone please give an alternate version of the circuit..But in m college they wont allow us to use microcontrollers as this is our first project.

Hey can someone gives me a cirucit that actually work??

 

[audioguru]

thanks everyone for their valuable reply.
Hey can someone please give an alternate version of the circuit..But in m college they wont allow us to use microcontrollers as this is our first project.

Hey can someone gives me a cirucit that actually work??

There are many modern circuits that work. But they are not on that horrible website in India.

 

[gtr_stitch]

I was actually experimenting with this circuit last night. Well, by that I mean it was late and I just threw it together but it seemed to work pretty decently. I used a piezo (which I still find to be awesomely sensitive). The cool thing I thought about this particular circuit is it's minimalistic design. You should check it out, and with some tweaking might be a good starter for what you need.

 

[audioguru]

I was actually experimenting with this circuit last night.

A piezo transducer is stiff so it has a high audio frequency resonance where it is most sensitive. It is not sensitive to low frequencies.
Your transistor is an emitter-follower with no voltage gain and it is overloaded by the headphones.

So what can it hear?

 

[gtr_stitch]

Actually, yea, good point Audioguru. I didn't tinker with it much, but I just tapped it a couple of times and I could hear it. Not as sensitive as when I was working on a guitar amp, though. I guess that wouldn't work as well when used as a heartbeat monitor.

Side note, I really do enjoy your isnight on matters like this I've seen a lot of your posts and can always count on you to be informative!

So as far as the monitor goes, could you use an electret mic with a 386 and implement a low-pass filter to hear a heartbeat?

 

[audioguru]

Hee, hee. If you can pull out your heart so it can tap your piezo transducer then you will hear your heartbeat!

I heard my heartbeat loud and clear with this circuit that was on two other websites that didn't work until I fixed it. I used a plastic lid from a jar to hold the mic and used over-the-ear headphones to avoid acoustical feedback howling.

 

[gtr_stitch]

Oh yea! I was checking that circuit out the other day. Do you really need two 9-volts? And what's up with the shielded wire? Is that essential?

Lol If I were to pull my heart out, I would think at that point I wouldn't need to hear it...I just went from audio to visual then a few seconds later I die...

 

[audioguru]

Do you really need two 9-volts?

The minimum voltage for a TL07x opamp is 7V and a little 9V battery quickly drops to less. A 12V battery can be used instead if the opamps are re-biased for a single-polarity supply.

And what's up with the shielded wire? Is that essential?

Yes.
There is plenty of gain and if the circuit is anywhere near civilization then unshielded input wires will pickup a lot of mains hum.

 

[gtr_stitch]

Ah okay lol yea, that makes sense. I think that would be a little bothersome trying to listen to a pulse and all you hear is just this steady hum. I used to work construction and there was this large transformer connected to the building and, as usual, it was always humming. Some days it drove me nuts, but other days I tried to hum along with it. And being a musician as well, of course, I was harmonizing with it. Hmm... I may have ADD...