Problem with a heartbeat monitor circuit

[ranggaperdana_06114]

Heartbeat Monitor

how if i use resistor film ? it's better isn't it?

 

[Audioguru]

Re: Heartbeat Monitor

how if i use resistor film ? it's better isn't it?

100 years ago all resistors were "carbon composition". They were horrible.
50 years ago most resistors were carbon film. They were fine but created a little noise.
20 years ago the best resistors were metal film. They were excellent.

Today, most consumer electronics are made with carbon film resistors.
Very expensive and high quality audio equipment use metal film resistors.

 

[ranggaperdana_06114]

Re: Heartbeat Monitor

it's fo located between R3 and C8 ?
how i can calculate the gain at R9 and R10?

 

[Audioguru]

Re: Heartbeat Monitor

it's fo located between R3 and C8 ?
how i can calculate the gain at R9 and R10?

Fo of the notch filter is calculated with the formula when the resistors and capacitors have the correct ratios (your resistors are not).

The gain of a non-inverting opamp is shown here:

 

[LvW]

Re: Heartbeat Monitor

Hi AUDIOGURU !

I am surprised, didn´t you forget something ?
You show as a circuit with the 741 opamp without saying that it is a lousy old amplifier ?
(Don´t be angry; but you certainly know that I am joking).
LvW

 

[Audioguru]

Re: Heartbeat Monitor

Hi AUDIOGURU !

I am surprised, didn´t you forget something ?
You show as a circuit with the 741 opamp without saying that it is a lousy old amplifier ?
(Don´t be angry; but you certainly know that I am joking).
LvW

I mentioned the lousy old 741 opamps on August 9th.
Maybe he can't buy better opamps in his country.
Maybe he likes the hisssss from the lousy old 741 opamps.

 

[aredhel]

Re: Heartbeat Monitor

Audioguru and to anyone, do you know the reasons why a hardware may and may not work at times? I have done the PCB and there were times where I could not get any signal and times where it works perfectly.

I tried using either TL071 or OP177 for the filters and AD620ANZ/INA121PA for the IA. There aren't anything wrong with my connections and I used bypass capacitors for double supply with fresh 9V batteries. The hardware goes bonkers at random times even with fresh batteries. Decided to buy new components and the result is the same: random craziness.

 

[Audioguru]

Heartbeat Monitor

The inputs to the AD620 do not have a 0V reference so sometimes the patient's body produces a positive or negative common-mode voltage that is too high for it.

 

[ranggaperdana_06114]

Re: Heartbeat Monitor

what is the function of all filter at this circuit?
in notch filter the fo is 50 Hz this frequncy is use for what?
tanx

 

[Audioguru]

Heartbeat Monitor

Mains hum interference pickup is at 50Hz in your country. But the harmonics of 100Hz, 200Hz and 300Hz are not eliminated with a 50Hz notch filter.

Take the project way out in a desert where there is no 50Hz mains hum and then you don't need the 50Hz notch filter.

 

[ranggaperdana_06114]

Re: Heartbeat Monitor

what is range frequency of ecg ?

 

[Audioguru]

Heartbeat Monitor

Some have a frequency range of 0.03Hz to 100Hz.

 

[aredhel]

Heartbeat Monitor

Hahahaha, thank you Audioguru. The circuit works now. Anyway I have a question on PCB design where I did a PCB with a polygon plane pouring all over the ground connections and another without it.

The one without the ground polygon plane gives a much "cleaner" output compared to the one with the ground polygon plane. Do you know what might be the reason ... is EMC and all that harmonics some of the reason and the plane is acting like an antenna?

Attached are images of the PCB design. The ground plane is poured on the bottom layer where the tracks are.

Thank you.

 

[Fragrance]

Re: Heartbeat Monitor

Hahahaha, thank you Audioguru. The circuit works now. Anyway I have a question on PCB design where I did a PCB with a polygon plane pouring all over the ground connections and another without it.

The one without the ground polygon plane gives a much "cleaner" output compared to the one with the ground polygon plane. Do you know what might be the reason ... is EMC and all that harmonics some of the reason and the plane is acting like an antenna?

Attached are images of the PCB design. The ground plane is poured on the bottom layer where the tracks are.

Thank you.

can you please share your final schematic

regards
Fragrance

 

[ranggaperdana_06114]

Re: Heartbeat Monitor

Hahahaha, thank you Audioguru. The circuit works now. Anyway I have a question on PCB design where I did a PCB with a polygon plane pouring all over the ground connections and another without it.

The one without the ground polygon plane gives a much "cleaner" output compared to the one with the ground polygon plane. Do you know what might be the reason ... is EMC and all that harmonics some of the reason and the plane is acting like an antenna?

Attached are images of the PCB design. The ground plane is poured on the bottom layer where the tracks are.

Thank you.

please share your circuit.... with us if you don't mind...
cause we all study here together...
tanx

 

[ranggaperdana_06114]

Re: Heartbeat Monitor

Some have a frequency range of 0.03Hz to 100Hz.

how if i use frequency range at 0.5 to 100Hz?
in that circuit (untitled.gif) all resistor i use is metal film resistor and all capacitor i use capacitor film. am i right?
how if i use elco at C2,C4,C5,C6,C7 & C8 it's okay?
tanx

 

[Audioguru]

Heartbeat Monitor

Metal film capacitors have a tolerance of 5%, some are 2%. Pretty good.
Elcos have a tolerance of +100% and -50%. Pretty bad.

 

[ranggaperdana_06114]

Heartbeat Monitor

how i can find the theory all about capacitor?

 

[Audioguru]

Heartbeat Monitor

Use Google to learn about simple highpass and lowpass filters.
The Sallen and Key filter is good.

 

[ranggaperdana_06114]

Re: Heartbeat Monitor

in my attachment, what is R12 and C6 is use for and what happens if i change it?
what i must to do to know the signal that i can get from this circuit and tell me how i can measure it in osciloscop?
tanx