IR questione

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I am to build this:

http://www.johnhenryshammer.com/...

and wonder:
Ii the upper left corner there are an IR-detector. Is it turned rhe right direction, anode to +5V?

The 10uF cap. May I use el.lyt?
Tantal?
+ to IC-pin1?

HM

HM

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That IR detector is actually a photo-transistor, not a diode. See the data sheet and make sure that you have it the right way round. It's usually used with a 10k resistor.

An electrolytic or tantalum should be OK.

Leon Heller G1HSM

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I am really puzzled about why a detector would be connected to the output pin of an op-amp. I suspect that someone has not copied the circuit correctly.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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That is strange, especially as the pin details are provided.

Leon Heller G1HSM

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The lower (by diagram) terminal of "blocking cap" shall go to pin #2. It's typo since the second op amp is wired correctly.
Would suggest OP taking a look on recent thread dated May 22nd - "Optical Heart Rate Monitor".

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leon_heller wrote:
That IR detector is actually a photo-transistor, not a diode. See the data sheet and make sure that you have it the right way round. It's usually used with a 10k resistor.

An electrolytic or tantalum should be OK.

Worse.
The light emitter are an TIL31.and the senso are unknown. Properly a TIL81. They are picked ftom an old 5 1/4 diskette drive.

HM

HM

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This circuit doesn't make a whole lot of sense to me, in a number of places.
the SEN-00241 detector is a transistor, not a diode as shown in the schematic.

The output of the detector connects directly to the output of one of the op-amps, not the input, so it's going to be overridden by the op-amp.

The second and third high pass filters are actually low pass filters. The capacitor in the negative feedback path reduces the gain as the frequency increases.

The 10K pot labeled as setting gain appears to be connected so as to set the DC reference level for both op-amps. The pot labeled as setting the voltage reference appears to be in series with the input of the third filter, and therefore would be setting the gain of the last stage.