I'm trying to build an IR proximity sensor using a simple tutorial found online. Here is the schematic Schematic

and here is the link of the tutorial : https://www.instructables.com/id/IR-Proximity-Sensor-1/

I wired it using solder lines and checking it with a multi-meter doesn't show any short. Front Back

there is a video which demonstrates how it works and it works for them (They used 2 IR LEDs). Here is the video link : https://www.youtube.com/watch?v=y83o_gfQRN8&feature=emb_title

But when activating it, the LED only turns on, the IR sensor and Photodiode doesn't give any impact from the output whatsoever. Giving it an opaque barrier doesn't help and turning the potentiometer slightly down only turns it on and off.

Reading the output signal with a serial plotter in arduino gave me these results : Output Readings

As you can see, there is a point where the output rose up dramatically. That's the point where the potentiometer turns on the LED, while the point where it is at zero is the near exact point the LED turned off while turning the potentiometer. It only has like less than a degree difference. Putting my hand near and far the IR receiver-transmitter doesn't change the output even the slightest. Any suggestions? Is it possible that the potentiometer i am using is the wrong kind or is it possible the photodiode does not give a strong enough signal?

  • 2
    \$\begingroup\$ Please give the part number of the op amp that you are using. \$\endgroup\$ – Elliot Alderson Dec 5 '19 at 12:44
  • \$\begingroup\$ Looks like your potentiometer says 104. That's 100k ohms. Cannot verify that other resistor colour codes are correct (bad photo). The 100k potentiometer is fine - should still work. In a dark room, take a photo (with no flash) looking straight down the IR LED. You should see a dim purple glow - indicating that it is emitting light. Using a 2-pin phototransistor instead of IR LED as photodetector can make this circuit much more sensitive. \$\endgroup\$ – glen_geek Dec 5 '19 at 15:02
  • \$\begingroup\$ my potentiometer is 103 not 104, sorry about that. as for part number, i am using an LM358P, there is another serial which is 87W09SFE3. as for the IR LED, i think the seller gave me a blue led instead because it glows a bright blue-purple color, but somehow, i saw other people used the same led as i did and it works, the LED goes bright and dim. \$\endgroup\$ – 3MP The Rook Dec 5 '19 at 16:51

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