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nareshbhar
Joined: 16 Jan 2009
Posts: 10
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 16 Mar 2009 19:23 ecg pulse oximeter multiplexer |
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Hi all,
Actually i am making pulse oximeter as my project.
I am using OPT101 as RED & IR detector, and output of the detector is connected to instrumentation amplifier AD630 as shown in schematic and rest of circuit is connected as shown in schematic.CD 4053 is analog multiplexer which is used to separate out RED & IR detector output signal.
but i am not getting expected result at output point(e.g. Point D,E,F,G),so pls anyone could figure out the problem with circuit,specifically filters.
please give your views,& if any alternate circuits.
Thank You.
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Audioguru
Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada
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17 Mar 2009 5:49 pulse oximeter canada |
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| The inputs of the AD620 need a resistance to ground through a patient. The patient needs a negative common-mode feed usually to the right leg which is near the ground voltage. Then the inputs of the AD620 will work.
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nareshbhar
Joined: 16 Jan 2009
Posts: 10
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17 Mar 2009 17:46 shematic cd4053 |
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but my sensor is finger sensor,and it has nothing to do with direct body contacts.
it just transmits the red & ir light which passes through finger and then received by detector.
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Audioguru
Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada
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17 Mar 2009 23:01 gnd an ad620 |
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You showed an ECG circuit.
When signal C1 goes high then the ECG output from the instrumentation amplifier is routed to the upper lowpass filter.
When signal C1 goes low then the ECG signal is routed to the lower lowpass filter.
There is no IR nor red detector circuit.
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nareshbhar
Joined: 16 Jan 2009
Posts: 10
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18 Mar 2009 18:20 Re: Pulse Oximeter |
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how can you say that its ECG circuit?. i think one can not say anything about circuit's application by just watching schematic.
and about analog multiplexer, its used to differentiate red & ir detector output,which is coming from one light detector only.
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Audioguru
Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada
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18 Mar 2009 21:41 Pulse Oximeter |
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Your ECG circuit does not have inputs for an IR detector and a Red detector. Instead it has an instrumentatation amplifier (look on the datasheet of the AD620 for an ECG circuit similar to yours) that has its output switched to 2 identical filters.
Only 1 of the 3 switches in the multiplexer is switched.
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nareshbhar
Joined: 16 Jan 2009
Posts: 10
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29 Mar 2009 14:08 Re: Pulse Oximeter |
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yes,actually i have taken this circuit from datasheet only,and as i need two differnt filter so as i can get two outputs,one bieng red detector and one being ir detector.
actually problem with the circuit is that it is not filtering out my desired signal which is around .6hz to 1.5hz.so,can you suggest any change in filter design.
Thanks.
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Audioguru
Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada
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29 Mar 2009 15:53 Pulse Oximeter |
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Your schematic does not show an IR detector and a red detector. It just shows part of an ECG circuit with some filters.
The lowpass filters pass frequencies below about 17Hz.
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nareshbhar
Joined: 16 Jan 2009
Posts: 10
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29 Mar 2009 19:00 Re: Pulse Oximeter |
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yes, I havn't shown the red & ir detector circuit.
I am using one detector with detecting range of 550nm-850nm.
I have connected my detector output to the input of instrumentation amplifier.
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29 Mar 2009 19:00 Ads |
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ronydc
Joined: 17 Nov 2005
Posts: 148
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30 Mar 2009 20:47 Pulse Oximeter |
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WHY U EXPECT RESULTS HERE WITHOUT SHOWING THE red and ir DETECTOR CIRCUITS HERE .?
THINK..
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ostik
Joined: 18 Apr 2009
Posts: 1
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18 Apr 2009 18:38 Pulse Oximeter |
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| hi im also making a pulse oximeter, if anyone can pls help me with the software pls. upload an example of a program so i know what its expected to look like atleast. im very new 2 this whole design thing n this is my first project. a schemetic would also be nice
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