Heartbeat Monitor

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Heartbeat Monitor
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Audioguru

Joined: 19 Jan 2008
Posts: 521
Helped: 39
Location: Canada

23 Jul 2008 17:35 Heartbeat Monitor

Your circuit works pretty well.
I wonder where the small oscillation at about 9Hz is coming from.
Don't forget to add a supply bypass capacitor across each supply, maybe 100uF.

aredhel

Joined: 22 Feb 2008
Posts: 36

01 Aug 2008 15:19 Re: Heartbeat Monitor

I am wondering about that small oscillation too. Is there a website that you can recommend when it comes to interfacing the circuit with the PC through a USB cable and the use of ADC? By the way since all ECG signal has some negative peaks ... how should I do my ADC?

In addition to that I was told that I could use a comparator and after getting the output from the comparator I only need to interface the circuit with the PC. I have a USB port, no serial port. So I was thinking of using a cable that has a RS-232 on one end while at the other is a USB. Do I only need to program the RS-232 on the circuit and then write a program in VB to call the signal from the USB cable? In order to send the signal to the RS-232 and then down the cable to the USB, do I need to use a PIC?

aredhel

Joined: 22 Feb 2008
Posts: 36

09 Aug 2008 12:25 Re: Heartbeat Monitor

Is there a way for me to supply the voltage with only one battery to the circuit?

Audioguru

Joined: 19 Jan 2008
Posts: 521
Helped: 39
Location: Canada

10 Aug 2008 5:53 Re: Heartbeat Monitor

aredhel wrote:

Is there a way for me to supply the voltage with only one battery to the circuit?

Any opamp will work with a single supply voltage if its inputs are biased properly at half the supply voltage.
With a dual polarity supply the inputs are biased at ground which is half the total supply voltage.

The lousy old 741 opamp needs a minimum supply voltage of about 12V. A few will work if the supply voltage is 9V.

Many modern opamps work if the supply voltage is from 3V to 36V.
But I can't attach my schematic because it was posted here somewhere before.
I changed its title and here it is:

I give up. I can't post it again and I can't find it here.
Every other electronics chat forum doesn't block posting the same schematic in different posts.

aredhel

Joined: 22 Feb 2008
Posts: 36

10 Aug 2008 11:03 Re: Heartbeat Monitor

Audioguru wrote:

Any opamp will work with a single supply voltage if its inputs are biased properly at half the supply voltage.
With a dual polarity supply the inputs are biased at ground which is half the total supply voltage.

The lousy old 741 opamp needs a minimum supply voltage of about 12V. A few will work if the supply voltage is 9V.

Many modern opamps work if the supply voltage is from 3V to 36V.
But I can't attach my schematic because it was posted here somewhere before.
I changed its title and here it is:

I give up. I can't post it again and I can't find it here.
Every other electronics chat forum doesn't block posting the same schematic in different posts.

Oh I have found the circuit, is it this:

http://www.electro-tech-online.com/attachments/general-electronics-chat/16566d1199899492-can-i-use-single-supply-tl074-opamps-2.gif

So all I have to do is supply +9V to V+ and ground V-?

Audioguru

Joined: 19 Jan 2008
Posts: 521
Helped: 39
Location: Canada

10 Aug 2008 16:31 Heartbeat Monitor

I am glad that you found my sketch.
A lousy old 741 opamp is designed for a 30V supply. Some won't work when the supply is only 9V and many won't work when the 9V battery voltage drops to 6V.

aredhel

Joined: 22 Feb 2008
Posts: 36

14 Aug 2008 12:08 Re: Heartbeat Monitor

I have decided to use PIC for my project and my connections on the 7-Segment side is based on http://web-ee.com/images/Schematic.pdf. I have a question though about the schematic. I have tried to contact the author, but no answer. Anyway the connection from the PIC to the 7-segment ... pins of RA0- RA4 and RB0 - RB6 ... they are all connected along a common line, because that is just ... odd.

Audioguru

Joined: 19 Jan 2008
Posts: 521
Helped: 39
Location: Canada

14 Aug 2008 16:18 Heartbeat Monitor

RA0 drives the base resistor for transistor U3 that drives the common cathode of the first digit.
RA1 drives the base resistor for the 2nd transistor.
RA2 drives the base resistor for the 3rd transistor.

RB0 to RB6 feed the current-limiting resistors for the segments of all the digits.

The digits are multiplexed so that only one digit lights at a time then the segments can be in parallel.

The schematic shows bundles of wires instead of showing all the wires separately.

aredhel

Joined: 22 Feb 2008
Posts: 36

26 Aug 2008 9:57 Re: Heartbeat Monitor

I tried to understand microcontroller and connect the PIC to the 7-segment. Yet everything flew right over my head and it did not work. Anyone knows any other options or could help me out with this?

aredhel

Joined: 22 Feb 2008
Posts: 36

30 Sep 2008 7:21 Re: Heartbeat Monitor

hello there ... again. my project is still at the edge of completion. my only problem now lies with the display of the heartbeat count. i was thinking of recording the heartbeat data using windows recoding software such as "Sound Recorder". then open the file in matlab. a small program will be written to count the heart beats. is this an OK way of doing it?

Audioguru

Joined: 19 Jan 2008
Posts: 521
Helped: 39
Location: Canada

30 Sep 2008 16:00 Re: Heartbeat Monitor

Heartbeat waveforms are at very low frequencies. Recording software and hardware don't have a response at such low frequencies. You might need response down to and including DC.

TekUT

Joined: 17 Jun 2008
Posts: 322
Helped: 22

01 Oct 2008 14:22 Re: Heartbeat Monitor

Could you please report in what position have put the sensor and what type of sensor are currently using?

Thanks
Pow

aredhel

Joined: 22 Feb 2008
Posts: 36

01 Oct 2008 14:54 Re: Heartbeat Monitor

I'm using electrode pads. The the right wrist eletrode pad is going to the -ve input of the IA while the positive input of the IA is from the left wrist electrode. The right leg input goes through the "right leg drive" circuit. The electrodes used are pretty much like this one: http://us.st12.yimg.com/us.st.yimg.com/I/cardioshop_2019_137478

TekUT

Joined: 17 Jun 2008
Posts: 322
Helped: 22

01 Oct 2008 15:13 Re: Heartbeat Monitor

Thanks for info.

Bye
Pow

Sam_t

Joined: 27 Oct 2008
Posts: 1

28 Oct 2008 14:19 Re: Heartbeat Monitor

Hello ! I've bought a mini blood preasure and heart beat device, digital ( portable ) and I don't know how to connect it to a electronic plate and then to the computer. How do I stick the wires to that plate ? I need it for my school project. I've attached some photos of the device. Please reply me a.s.a.p. it will mean the world to me. Thank you.

Sorry, but you need login in to view this attachment

Audioguru

Joined: 19 Jan 2008
Posts: 521
Helped: 39
Location: Canada

28 Oct 2008 17:17 Re: Heartbeat Monitor

Sam_t wrote:

Hello ! I've bought a mini blood preasure and heart beat device, digital ( portable ) and I don't know how to connect it to a electronic plate and then to the computer. How do I stick the wires to that plate ? I need it for my school project. I've attached some photos of the device. Please reply me a.s.a.p. it will mean the world to me. Thank you.

Fuzzy photos don't show the schematic of it.
What is "an electronic plate"?
It might not be designed to be connected to a computer.
If you have the schematic then maybe you could design a complicated interface circuit and make a complex computer program for it to connect to a computer.

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