infra-red liquid level detector

[Thanhlongbin]

liquid level measurement

I basically don't understand what you want to tell me. Seems like you are starting a new photo diode theory. But whatever you mention in this regard, it doesn't change the fact, that the shown basic circuit is operating fine. You say, the PD must be reversed to make it working. Obviously, one opinion is right and the other wrong. I think, the question can be answered by a simple test (or correct usage of semiconductor theory). I'm not motivated to add more arguments now.

Dear FvM,
I'm so sorry for my posted comments.
I've just tested PD in zero-bias mode using a voltmeter. The result is: -280mV at cathode vs. anode in sunlight.
I wish you accept my apology.
Thanhlongbin

 

[FvM]

infra-red water level detector

Dear Thanhlongbin,
I'm glad, that we can end the controversy in this regard. No need to apologize, I think.
Best regards,
Frank

 

[dumanmehmet]

I'd like to know that any of these circuits can measure distance from 8cm to 40 cm with 4cm presicion. I have a project to understand which self has a tray in an oven, but I have to use IR LED, I cannot use ultrasonic!. If you have any circuit pls send it to me. I try the NAND gates one with NE555, it works but not measure sensitively. the tray is black and bright. There are 5 shelfs in the oven. Only thing that I have to know which shelf has a tray. Thanks.