Medical Electronics

[audioguru]

The Texas Instruments article explains about the conditioned common-mode signal that is fed to the right leg and the DC offset cancellation circuit. I didn't know that a person would have an offset voltage as high as 300mV DC.
Opamps can drive a load of 2k ohms so 47k is fine.

 

[moonraker]

audioguru, if u dont mind, im also working on ECG but it is totally different because im thinking of sumthing like "portable ECG". could u help me with this? i need a circuit so that i can start. Thank you so much!

 

[audioguru]

audioguru, if u dont mind, im also working on ECG but it is totally different because im thinking of sumthing like "portable ECG". could u help me with this? i need a circuit so that i can start. Thank you so much!

This thread has a few ECG circuits. They are also "portable".
Try one of the good ones.

 

[littletransistor]

The Texas Instruments article explains about the conditioned common-mode signal that is fed to the right leg and the DC offset cancellation circuit. I didn't know that a person would have an offset voltage as high as 300mV DC.
Opamps can drive a load of 2k ohms so 47k is fine.

I see. Maybe I should go to my school's lab and use an oscilloscope. I suspect my configuration is working, since, many configurations of those ECG kits are usually hooked to an oscilloscope and not computer sets (I don't really know how to build an A-D converter and feed them to serial port!).

 

[beginner Wan]

hello sir/mam!!

good day!!

i' ve been following this thread and i learned lots of things.and i want to thank you sir for the facts that you shared with the readers of this thread. i have a question, this is a bit OT but still connected w/ biomed... can i use the same circuit for ecg to measure and monitor REM?coz i'm also working on a project.. a home made REM monitoring and a sleep apnea device. i already have an idea about the sleep apnea... the only problem is the REM... do you guys think that i can use the same or maybe a circuit that resembles this Hme-made ECG?

thanks sir...

w/ due respect..
beginner wan

 

[littletransistor]

hello sir/mam!!

good day!!

i' ve been following this thread and i learned lots of things.and i want to thank you sir for the facts that you shared with the readers of this thread. i have a question, this is a bit OT but still connected w/ biomed... can i use the same circuit for ecg to measure and monitor REM?coz i'm also working on a project.. a home made REM monitoring and a sleep apnea device. i already have an idea about the sleep apnea... the only problem is the REM... do you guys think that i can use the same or maybe a circuit that resembles this Hme-made ECG?

thanks sir...

w/ due respect..
beginner wan

For the REM device, you might need a different apporach - using a modified EEG device.

In the meantime, still I need to get a cheap oscilloscope, but they are darn expensive and not feasible for my pocket money!

 

[KMoffett]

Just happened across this when searching for something else:

https://www.eng.utah.edu/~jnguyen/ecg/instructions.html

Thought it might be of some help.

Ken

 

[audioguru]

Just happened across this when searching for something else:
https://www.eng.utah.edu/~jnguyen/ecg/instructions.html

He doesn't have a clue about circuit design.
For an "improvement" he recommends using the lousy old LM324 quad opamp and use only two of its four opamps. It is extremely noisy!
He doesn't know that the lousy old LM358 dual opamp has two of the same opamps that are in the LM324.

There are hundreds of low noise opamps available. There are many instrumentation amp ICs available.

 

[littletransistor]

He doesn't have a clue about circuit design.
For an "improvement" he recommends using the lousy old LM324 quad opamp and use only two of its four opamps. It is extremely noisy!
He doesn't know that the lousy old LM358 dual opamp has two of the same opamps that are in the LM324.

There are hundreds of low noise opamps available. There are many instrumentation amp ICs available.

Well, he's trying to keep it all low-cost, so he uses those older op-amps.

According to his suggestions, he recommended using electrodes and also an instrumentation amplifier (to simplify the job as well).

 

[Nigel Goodwin]

Well, he's trying to keep it all low-cost, so he uses those older op-amps.

He doesn't care if it doesn't work then? - and you can buy FAR better opamps at lower cost than 741's anyway!.

 

[audioguru]

The LM324 and LM358A cost exactly the same at Digikey. The much better TL072 dual audio opamp costs just 8 cents more.

 

[littletransistor]

He doesn't care if it doesn't work then? - and you can buy FAR better opamps at lower cost than 741's anyway!.

Yes ... and his page seems to be outdated too. I've contacted the author but he's missing in action.

Yeah, the 741s are way too old anyway. Still, I prefer instrumentation amps, and the cheapest one is being the INA126 by Burr brown.