Problem with a heartbeat monitor circuit

[Audioguru]

heart beat monitor in vb

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]

heartbeat monitoring circuit

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

Thanks
Pow

 

[aredhel]

heartbeat monitor russian

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

 

[Sam_t]

lm358 in heart beat 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.

 

[Audioguru]

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.

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.

 

[aredhel]

Re: Heartbeat Monitor

The project is almost done now, took a long time I know. I was wondering if anyone can suggest me better methods to hook myself to my hardware?

Right now I am using crocodile clippers with a normal jumper wire connecting the crocodile clip to the PCB. Since I planning to give my PCB a casing, does anyone know of another/better method of connection from the electrodes to the hardware?

 

[eng_shady00]

Re: Heartbeat Monitor

The project is almost done now, took a long time I know. I was wondering if anyone can suggest me better methods to hook myself to my hardware?

Right now I am using crocodile clippers with a normal jumper wire connecting the crocodile clip to the PCB. Since I planning to give my PCB a casing, does anyone know of another/better method of connection from the electrodes to the hardware?

Hi,
I've read all ur topics unil u've finished ur project. Congratulations!!!
First, about ur question, there is sockets something contents of 2 parts male and female.. it's something like snap fastener (like the one in ur shirt ).
There's also some thing similar to the audio jack with its female part which can be fixed in ur PCB.
Also ther're sockets called banana with 2 parts.
For all of the above, one part is fixed to ur board and the other connected to the patient cable.
U also may buy ECG patient cables which used in hospital's monitors. U can find it in shops of biomedical equipments.

I'm making a project of an ECG monitor. But the difference is that i want to display the signal on pc including calculating the heart rate in a small program using matlab's GUI. I've built my circuit but the same problem occurs, NOISE.
1-Can u please send the last design that give a clear signal.
2-Did u use all the HPF, LPF & Notch filters ?? or what?
3-Did u use an ordinary CRO to check ur signal ? I can't get a solid line signal on CRO, but i could adjust it to view a moving dot takes a shape of the ECG signal.
4-Did u use pic or adc.
5-Could u connect ur board to pc ? how ? Does the usb connection work?
Wish u may help me until i finish my project like u.
Thanks alot.

 

[aredhel]

Re: Heartbeat Monitor

Hi,
I've read all ur topics unil u've finished ur project. Congratulations!!!
First, about ur question, there is sockets something contents of 2 parts male and female.. it's something like snap fastener (like the one in ur shirt ).
There's also some thing similar to the audio jack with its female part which can be fixed in ur PCB.
Also ther're sockets called banana with 2 parts.
For all of the above, one part is fixed to ur board and the other connected to the patient cable.
U also may buy ECG patient cables which used in hospital's monitors. U can find it in shops of biomedical equipments.

I'm making a project of an ECG monitor. But the difference is that i want to display the signal on pc including calculating the heart rate in a small program using matlab's GUI. I've built my circuit but the same problem occurs, NOISE.
1-Can u please send the last design that give a clear signal.
2-Did u use all the HPF, LPF & Notch filters ?? or what?
3-Did u use an ordinary CRO to check ur signal ? I can't get a solid line signal on CRO, but i could adjust it to view a moving dot takes a shape of the ECG signal.
4-Did u use pic or adc.
5-Could u connect ur board to pc ? how ? Does the usb connection work?
Wish u may help me until i finish my project like u.
Thanks alot.

1. My last design did not give a better signal. But it is just these: ECG > IA > 4th order HPF > 2nd order LPF > Twin-T Notch > PC. Mind you the hardware is not stable. There will be times where the hardware works and times where everything just screws up.

2. Yup, used all three filters. Its cumbersome when designing the PCB, try using Matlab or something to filter out the noise and digital filters are better.

3. Yes, used an ordinary CRO, but its a digital CRO.

4. I'm using the PC's sound card as the ADC.

5. Connected the board to the PC using a microphone jack.

 

[ranggaperdana_06114]

Re: Heartbeat Monitor

i've try to make the heart beat monitor use this file that i've attachhed. and i want know the each of circuit, which is main circuit which is filter circuit, what the filter is use and what must i use to make a good filter but whit the familiar part.
tanx

 

[Audioguru]

Heartbeat Monitor

The AD620 is a instrumentation amplifier with differential inputs. It has a voltage gain set to 24.7 by R1. It needs the patient to be connected to the circuit's 0V to work properly.

U3 is a Sallen and Key 2nd-order highpass filter with a voltage gain of 2.7.

U4 is a Sallen and Key lowpass filter with a voltage gain of 2.7.

The notch filter is a passive Twin-T type with a very wide bandwidth.

U2 is an amplifier with a voltage gain of 9.

The lousy old 741 opamps are too noisy for this project.

The datasheet of the AD620 shows an ECG circuit with the patient's right leg fed a filtered common-mode voltage as a reference for the instrumentation amplifier.

 

[ranggaperdana_06114]

Heartbeat Monitor

what ic i must use to make not noise so small

 

[Audioguru]

Heartbeat Monitor

A TL071 low noise opamp has 1/3rd the noise of a lousy old 741 opamp.
An OP134 has 1/7th the noise of a lousy old 741 opamp.
An LM4562 dual opamp has 1/20th the noise of a lousy old 741 opamp.
There are many opamps better than a lousy old ...

 

[Audioguru]

Re: Heartbeat Monitor

how about OP17 ?

There is no opamp called an OP17 unless it is very old and is not made anymore.

 

[ranggaperdana_06114]

Heartbeat Monitor

ops.. i'm sorry. i mean with OP07 and OP97

 

[Audioguru]

Re: Heartbeat Monitor

ops.. i'm sorry. i mean with OP07 and OP97

The OP07 is pretty good and will work fine in this circuit. many of its features are not used.

There is no OP97.

EDIT: www.datasheetarchive.com does not list an OP97. But Google gave me a link to its datasheet. It is a low power opamp which means it is slow but is fine for a low frequency heartrate.

 

[eng_shady00]

Re: Heartbeat Monitor

A TL071 low noise opamp has 1/3rd the noise of a lousy old 741 opamp.
An OP134 has 1/7th the noise of a lousy old 741 opamp.
An LM4562 dual opamp has 1/20th the noise of a lousy old 741 opamp.
There are many opamps better than a lousy old ...

U've suggested using TL071 instead of 741.
For a heigher order LPF, can i use TL074?
I mean can i use each included op-amp as a separate one in a separate stage of my filter.
I hope my question is obvious.
What about LM358 and AD620.
Should i replace them also?

Please, I've another request:
Can u please help me in choosing an optocoupler isolator to use in my ECG circuit? A one with a suitable cost and that i can find in market.
I saw many data sheets, but can't choose one.
I've 3 patient leads, connected to right arm, left arm & left leg.
I want to separate the patient from the rest of the cicuit.
Will the optocoupler powered from my power supply?
Or this may also be dangerous for patient?
how can i fully isolate the patient?
Thanks in advance.
]

 

[Audioguru]

Re: Heartbeat Monitor

For a heigher order LPF, can i use TL074?

I have made 3rd-order Butterworth filters with a single opamp. Higher orders can be made with a TL072 dual opamp or a TL074 quad opamp.

What about LM358 and AD620.
Should i replace them also?

The LM358 is horrible. the AD620 is OK.

Please, I've another request:
Can u please help me in choosing an optocoupler isolator to use in my ECG circuit? A one with a suitable cost and that i can find in market.
I saw many data sheets, but can't choose one.
I've 3 patient leads, connected to right arm, left arm & left leg.
I want to separate the patient from the rest of the cicuit.
Will the optocoupler powered from my power supply?
Or this may also be dangerous for patient?
how can i fully isolate the patient?
Thanks in advance.

The patient side of an opto-isolator needs to be powered by something like a battery so you might as well power the entire circuit from a battery.

 

[eng_shady00]

Heartbeat Monitor

Thanks alot.
U really helped me and many others.
But please can u specify an opto-isolator. I wish it can be quad or multi, if their exist.
Also, What's the equevalent to LM358?
Best regards.

Also, can the opto-isolator be replaced with 2 diodes in reverse polar connected to ground for each lead.
If yes, how should i choose my diodes.
Thanks again

 

[Audioguru]

Re: Heartbeat Monitor

Thanks alot.
U really helped me and many others.
But please can u specify an opto-isolator. I wish it can be quad or multi, if their exist.
Also, What's the equevalent to LM358?
Best regards.

Also, can the opto-isolator be replaced with 2 diodes in reverse polar connected to ground for each lead.
If yes, how should i choose my diodes.
Thanks again

I went through this entire thread to find the circuit that shines an LED through a finger to detect blood flow.
It uses a lousy old LM358 dual opamp because noise doesn't matter and the supply to the opamp is only 5V.

It does not have an "opto-isolator". It has an LED shining though a finger to a light-dependent-resistor.

 

[eng_shady00]

Re: Heartbeat Monitor

It does not have an "opto-isolator". It has an LED shining though a finger to a light-dependent-resistor.

ya, i know that device cause i'm a biomedical engineer working in a hospital.
This eqquipment called a pulse oximeter or Spo2 which measures the saturation of blood with oxygen.
It's sensor called a finger probe. I intend to execute this circuit after completing my ecg.
I think it don't have a protection circuit for the patient as it depends on an LED and a light sensor.
But in ECG, we connect the leads to patient to acquire the signal, which may apply dangerous voltages or - more accurately we can say dangerous currents - to patient.
So, see the attached circuit. It's not mine, and not quite accurate, but i want u to notice the diodes at the patient side. Can them function well in protection just like the opto-isolator does. And how can i choose these diodes.
And also i can't choose a good opto-isolator. Can u help in doing so.
Finally, u think LM358 is quite good?

Sorry for interruption.
Thanks