Problem with a heartbeat monitor circuit

[LvW]

heart beat monitoring circuit

I only know of the Wein Bridge and the Twin-T ... been looking for other notch topologies. Could you recommend some?

Highpass: Do you need a highpass of 2nd order ? If not, there is a 1st order topology which is best suited for low frequencies: A simple RL-highpass scheme with active simulation of the inductor using two opamps (gyrator principle using the impedance converter structure).

Notch: The best circuit - as far as dimensioning is concerned - is a structure based again on the impedance converter principle. However, two opamps are required. Two other one-opamp topologies are based on the multifeedback-bandpass filter. If necessary I could send you a schematic.

 

[aredhel]

project on heartbeat monitoring

Highpass: Do you need a highpass of 2nd order ? If not, there is a 1st order topology which is best suited for low frequencies: A simple RL-highpass scheme with active simulation of the inductor using two opamps (gyrator principle using the impedance converter structure).

Notch: The best circuit - as far as dimensioning is concerned - is a structure based again on the impedance converter principle. However, two opamps are required. Two other one-opamp topologies are based on the multifeedback-bandpass filter. If necessary I could send you a schematic.

Yes please, I would like to have the schematic for the Notch and HPF.

 

[LvW]

heartbeat monitor

See the attachement for some circuits which I propose to you.
Good luck.

 

[aredhel]

ad623 ekg

I finally got the signal. It looks clean, but this was achieved with the 741. I will try the circuit with the LT071 and OP177. Right now I am looking at ADC in order to do my heart beat count. Could anyone suggest some good sites for me to visit on this topic? I am having trouble understanding about ADC at the sites I've visited.

 

[siegmar]

ad620 gain ratio not stable

Hi
Have a look to the TI Application.
**broken link removed**
The digital filter is working well. I tested it.
With best regards
Siegmar

 

[aredhel]

driven righit leg with tl081

Thank you for the link siegmar. I am wondering if anyone has any experience in sending analogue data from their circuit to the microphone slot of their computer? I was wondering whether analogue-to-digital conversion needs to be before the transfer to the microphone slot or after that? If it is after then is it possible to convert from analogue to digital in VB itself? Last question is on the ADC. For an ECG signal, which ADC IC works best or any applies regardless of the IC's specs?

 

[Audioguru]

heartbeat.wav cs 1.6

A computer's mic input probably does not have the response at very low frequencies that is needed for heartbeats. It is an analog input, not digital.

You need to digitize the signal with an aDC then feed the digital info to the computer.

 

[aredhel]

heartbeat crm monitor not working

I am having trouble connecting my circuit to the microphone socket, so I am thinking of connecting my breadboard to the PC using USB. On the breadboard I am using the USB socket/port which then I will connect a USB cable from there to the USB port of the PC. However, I am having confusion over the connections of the USB socket over at the breadboard. After doing my ADC on the ECG output do I straight away feed the signal to the USB socket and then connect a USB cable from that socket to the PC's USB port?

 

[Audioguru]

biopotentials.pdf

Your schematic does not show the supply voltages. If the supply is dual polarity then the output swings positive and negative. The negative swing will destroy an ADC and the positive swing must be reduced to 5.0V.

The circuit that I posted operates its modern opamps from a single positive 5V supply. Many old 741 opamps do not work when the supply is as low as 5V because they were designed and spec'd for a 30V supply.

 

[aredhel]

op07 op134

I couldn't get hold of the single supply op-amps and instrumentation amplifiers. I could only find SOIC packaging, there are no DIP. Anyway attached is the new schematic along with the drive-right-leg. I am supplying 9V from two 9V batteries. The +ve from battery A with the -ve of battery B were bridged to make the ground, where everything that are grounded are connect to this point. The remaining +ve and -ve are used to supply positive and negative voltage to the dual op-amp.

 

[Audioguru]

heartbeat monitor circuit.pdf

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]

heartbeat monitor circuit using cro

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]

heartbeat monitor schematic

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

 

[Audioguru]

opamp datasheet ecg right leg drive

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]

heart beat monitor simple 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.

Oh I have found the circuit, is it this:


https://www.electro-tech-online.com...92-can-i-use-single-supply-tl074-opamps-2.gif

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

 

[Audioguru]

effect the value of resistor in 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]

simple heart beat mopnitor project circuit

I have decided to use PIC for my project and my connections on the 7-Segment side is based on **broken link removed**. 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]

principle of digital heart beat 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]

principle of digital 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]

lt071 amplifier

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?