Two pin IR reciver LED configuration [SOLVED] - Page 1
Forum section: electronics / general

author: amir.razzaqi
author_rank: Contributor
timestamp: September 03, 2023, 08:37:30 pm
content: :palm:HelloI want to see IR remotes carier signal using single two pin IR reciver diode connected to osciloscope. How to config this diode on breadboard and what voltage do I use?I appreiciate any help or schematic circuit

author: Zero999
author_rank: Super Contributor
timestamp: September 03, 2023, 09:09:32 pm
content: Connect the diode in reverse series with the power supply, with a resistor to 0V.http://electron6.phys.utk.edu/optics421/modules/m4/detectors.htm

author: amir.razzaqi
author_rank: Contributor
timestamp: September 04, 2023, 05:44:22 am
content: Quote from: Zero999 on September 03, 2023, 09:09:32 pmI use 2 different possible configuration according to the attached photo. by aiming TV remote to the IR receiver, scope in first config show continuous +5V and in the second config show fix 0 Volt. it does not react to IR light emitted from TV remote completely.

author: Ian.M
author_rank: Super Contributor
timestamp: September 04, 2023, 07:00:46 am
content: The photodiode in photovoltaic (zero bias) mode will react to the RC modulation envelope if connected directly across the scope input (DC coupled) with no other parts, if the IR illumination is strong enough. It wont be fast enough to resolve the typ. 38KHz carrier. You need to get the remote's IR LED within a couple of cm of the photodiode, and shield the photodiode from direct room lighting - a few cm of black rubber tubing is ideal.When I used to work in a TV shop, we kept a BNC connector with a photodiode connected as described, permanently on one of our scope channels, only removing it if we needed all channels for a particular job.To resolve the carrier, you'd need to run the diode in photoconductive (reverse biassed) mode and minimise the effect of the photodiode's junction capacitance, which would probably require a transimpedance amplifier. Due to varying ambient lighting you'll probably need to servo the bias voltage to keep the output between the rails.

author: amir.razzaqi
author_rank: Contributor
timestamp: September 04, 2023, 07:13:54 am
content: Quote from: Ian.M on September 04, 2023, 07:00:46 amdoes IR receiver Diode has photovoltaic feature?

author: Ian.M
author_rank: Super Contributor
timestamp: September 04, 2023, 07:23:05 am
content: If its a simple IR photodiode, yes. However the relatively small junction area means the available current will be tiny, even under strong IR illumination, and even the 1Meg input impedance of a DC coupled scope input will load it significantly.If it *not* a simple photodiode (i.e its a phototransistor or any other sort of amplified photodetector in a two pin package), then you cant use photovoltaic mode and will need to consult its data sheet for its typical application circuit to bias it correctly to get a useable output.

author: StillTrying
author_rank: Super Contributor
timestamp: September 04, 2023, 12:25:14 pm
content: The left side of that breadboard is wrong, both ends of the diode are in the same track.You'll have to have the IR diode and TV remote facing each other <15 mm distance for a few 10s of mV output.A mobile phone camera can see the IR from remotes.

author: amir.razzaqi
author_rank: Contributor
timestamp: September 04, 2023, 02:45:47 pm
content: Quote from: StillTrying on September 04, 2023, 12:25:14 pmThank youThis is so embarrassing mistake