IR and Photodarlington circuit doubt

Thread Starter

medic mad

Joined Oct 10, 2015
15
I am a noob in circuits

i want to detect minor changes in fiber optic sensor.

I use IRL81 as source and OP560A as Photo detector.
100HZ 50% duty cycle has used from arduino to fire the LED

[Lockin amplifier, phase detector, synchronous detector, voltage mixer, phase locked loop are confusing me]

In my application what i have to use?

20151010_134021_800x580.jpg
 

ScottWang

Joined Aug 23, 2012
7,081
The files size that you attached were too too big, I was compressed them to the normal size, they are from about 2.25MB compressed to about 51KB, next time before you upload the files, please compress the photos to 800x600 or 640x480, if necessary then you can compress to 1024x768, almost the photos using 800x600 image is enough.

Too much file size will affecting the connecting speed of members get to the forums, thanks for your understanding and cooperation.
 

ericgibbs

Joined Jan 29, 2010
14,245
hi,
It would help, if you told us what you are trying to do with this project.?
I assume when you say fibre optic 'sensor' you mean 'link'.?
E
 

Thread Starter

medic mad

Joined Oct 10, 2015
15
yes to sense antigen...refractrometer application

i am confused what i have to use?[Lockin amplifier, phase detector, synchronous detector, voltage mixer, phase locked loop ]

Capture.jpg

mod edit:
You were used the wrong file format, photos should be using *jpg, png file was used for simple graphics and less color, specially as vertical and horizontal line, the file that I already converted to the jpg file.
 

Alec_t

Joined Sep 17, 2013
12,321
If your mains frequency is 50Hz then 100Hz is a poor choice for the drive pulse frequency, since there is likely to be a lot of interference at harmonics of the mains frequency. A stable, high quality instrumentation amplifier would be needed for good sensitivity to minor amplitude changes. I think phase change detection would require optical interferometry.
 

Thread Starter

medic mad

Joined Oct 10, 2015
15
If your mains frequency is 50Hz then 100Hz is a poor choice for the drive pulse frequency, since there is likely to be a lot of interference at harmonics of the mains frequency. A stable, high quality instrumentation amplifier would be needed for good sensitivity to minor amplitude changes. I think phase change detection would require optical interferometry.

thanks for your valuable reply sir

how about 1khz frequency and 100 gain of instrumentation amplifier?

after that what i have to do? any syggestions
 

Thread Starter

medic mad

Joined Oct 10, 2015
15
concept:
I use IRL81[LED] as source of 1KHZ 50% duty cycle PWM and OP560A[photodarlington] as Photo detector .
Connecting source and detector via Fiberoptic with small Portion decladded where different samples to be introduced.
When samples introduces in the decladed fiber there is a Changes in intensity. This change in intensity changes the Photo Darlington(PD) voltage
now i need to find the difference between the reference signal 1khz 50% duty cycle PWM and PD.

prob:
Need to detect change in amplitude as well as phase.

i recently posted same question here , i'm getting confuse with the followup's

Working model: i used 1khz 50% duty cycle(don't get confused as shown in Image 100hz)


Connection between IR and PD
 

Attachments

Alec_t

Joined Sep 17, 2013
12,321
I think any phase change would be undetectable using the proposed system. The sample might change the light propagation time by a few picoseconds if you're lucky; but how would you sense that without very sophisticated circuitry?
 

Thread Starter

medic mad

Joined Oct 10, 2015
15
I think any phase change would be undetectable using the proposed system. The sample might change the light propagation time by a few picoseconds if you're lucky; but how would you sense that without very sophisticated circuitry?
In that case shall i go with lockin amplifier. Is it Recommended for my application.
 
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