Need Help Connecting Microphone for ECG project

[sugarmeaowl]

hellppp guyzzzzz

guyzz plzz helpp
i wanted to ask u abt my ecg project. i have built the circuit on breadboard and now i hav to connect it to my microphone port.. please tell me wat cable can i use to connect my breadboard to my microphone port. plzzz help guyzzzz do not ignoree

 

[Audioguru]

hellppp guyzzzzz

Use shielded audio cable.

 

[sugarmeaowl]

Re: hellppp guyzzzzz

dear sir,
will this be aryt as mentioned in the link below. please if u can hav a look

**broken link removed**

so this sheilded wire will easily be connected to m breadboard and then to microphone port of the pc?
is there any special pattern that i have to follow in order to use it.

sir below is my schematic for my ecg. is this ok?
and den i wanted to askk that u see that pin number 5 of HCPL7800 is coonected to that triangle sign... is that signal ground? how can i use it..
and then pin number 6 of HCPL7800 is connected to nothin? am i right.

third things are there any speical ecg leaads that i hav to buy or sumthin?

plzz helpp mee sirr
thank youu vry mchh

 

[Audioguru]

hellppp guyzzzzz

You can use the over-priced Maplin cable if you want. I use cables that come with all record players, cassette recorder/players, CD and DVD players and my cable TV decoder.

Don't use a breadboard because the wires will pickup interference and the contacts are intermittent. Use a compact pcb or stripboard.

Look at the datasheet for the HCPL7800 to see what it does. It isolates so that the patient is not electrocuted. The patient's electronics has two 9V batteries powering it and has its own ground (pin 4) that is shown with a triangle with 4 lines and the output electronics is powered from a mains power supply that is shown with an open triangle ground (pin 5). The two grounds are completely separated.
Pin 6 is not connected to anything.

You need conductive ECG electrodes to stick on the patient. The shields of the cables do not connect to the patient.

 

[sugarmeaowl]

Re: hellppp guyzzzzz

sir,
i dunt understand dis pin 5 thing. i know its grouned and is different from pin 4. pin 4 is da earth ground da normal one init. .. and pin 5 is i guess signal ground. but u see there are like 6 or 7 those triangle shape grounds... can u plz elleborate on tht plzz??. im confused with how to connect those ?

nd i wash thinkin to read the data on matlab by microphone port.. it can b done by using wave funcition is'nt it?

 

[Audioguru]

hellppp guyzzzzz

Please write in English with proper spelling. I don't understand half the things you say.

Connect all the grounds of each type together so you have an input ground between the two 9V batteries and an output ground that connects to a mains power supply and to your computer or recorder.

 

[sugarmeaowl]

Re: hellppp guyzzzzz

so you mean that all the triangle grounds are connected together to the power supply 0 VOLT?

 

[Audioguru]

hellppp guyzzzzz

There are two different triangle grounds. The input grounds are tied together and the output grounds are tied together.

The input ground is isolated from the output ground and the input circuit is isolated from the output circuit so that the patient does not get electrocuted if the output circuit becomes shorted to the mains high voltage.

 

[sugarmeaowl]

Re: hellppp guyzzzzz

okkk sirr i understand what exactly your trying to say.
noww this analog output signal can be accessed from matlab.
iam thinking to connect my microphone port to the circuit which will work as ADC converter and treat in matlab using the wave function. is it possible?
or is there any other easier wayy to do interface with the pc?

 

[Audioguru]

hellppp guyzzzzz

The output of the ECG circuit goes up to positive 8V and negative 8V. Your mic input of your pc is destroyed if its voltage is higher than +5V or more negative than 0V.

 

[sugarmeaowl]

Re: hellppp guyzzzzz

shyttt ... then how can i interface my circuti with the pc? using rs232?
how can i shoow the signalls on pc then?

Added after 4 minutes:

OR sir if you have any other better circuit diagram to build an ecg?
that can easily be connected to the microphone port of the pc and then the graphs can be easily be shown on matlab.

 

[Audioguru]

Re: hellppp guyzzzzz

then how can i interface my circuti with the pc? using rs232?
how can i show the signalls on pc then?

It is simple to attenuate the signal to 5Vp-p with 2 resistors and bias it so that it is never a negative voltage.

 

[sugarmeaowl]

Re: hellppp guyzzzzz

sir
do u mean that i have to process by 2nd order Butterworth BPF, which is shown in the circuit attached below.
and then i connect it to the microphone port?

 

[Audioguru]

hellppp guyzzzzz

You show a droopy second-order highpass filter and an unusual second-order lowpass filter. They are not Butterworth.

The output will be plus and minus 7.8V which will blow up the microphone input of a pc.

 

[sugarmeaowl]

Re: hellppp guyzzzzz

it is gettin a little confusing .... so what exactly do you recommend me sir?..

do you have any other better ecg circuit?

 

[Audioguru]

hellppp guyzzzzz

Your signal goes to a negative voltage that will destroy the mic input of a pc.
Your signal also has a level that is much too high so it will also destroy the mic input of a pc.

 

[sugarmeaowl]

Re: hellppp guyzzzzz

okk sirr i gott it that it will destroy the microphone port.
so what way do u recommend me to do it?

 

[Audioguru]

Re: hellppp guyzzzzz

okk sirr i gott it that it will destroy the microphone port.
so what way do u recommend me to do it?

Repeat: "It is simple to attenuate the signal to 5Vp-p with 2 resistors and bias it so that it is never a negative voltage."

 

[sugarmeaowl]

Re: hellppp guyzzzzz

what value resitors i can use? and shall i connect the resistors at the output of the ecg

 

[Audioguru]

Re: hellppp guyzzzzz

what value resitors i can use? and shall i connect the resistors at the output of the ecg

Of course the attenuator must be connected to the output of the ECG circuit. Check the max allowed input signal level of the mic input of your pc and make a suitable attenuator. Bias the signal so it never goes negative.