IR receiver sans op-amp

Other Hardware General Electronics
1

I’ve decided to investigate IR codes and sensing thereof with the Arduino. I have the UNO starter kit and this emitter/receiver assembly out of a paper shredder.

SAM_2449.JPG
SAM_2449.JPG1920×1080 301 KB

The consensus on the web is to use the IR sensor to drive an LM358 opamp to get a useable signal. However, the kit has a few BC547Bs (small signal NPN) but no opamps – and I’m not really up for making up a parts order to get one IC. Is there some circuit I could put together using one or more BC547Bs to get a good logic level signal? I was thinking something like this:

opto IR.PNG

Or, maybe two BC547s in a Darlington configuration? Is it even possible with just a couple of transistors?

I also have a 74HC00 if that would help.

SAM_2449.JPG
SAM_2449.JPG1920×1080 301 KB

opto IR.PNG

2

IR signals are double modulated (38kHz and data).
A 3-pin IR receiver takes care of (removes) the 38kHz part,
so only the remote data is left for the Arduino to decode.
A simple IR photo diode would pass the double modulated signal to the Arduino.
Doubt that IR libraries can decode that.
Leo..

3

Wawa:
A simple IR photo diode would pass the double modulated signal to the Arduino.
Doubt that IR libraries can decode that.

Oh. Rats! Thanks for the info, I just *assumed * the Arduino was doing everything.

Any thoughts on whether the receiver out of a junk TV or some such would provide a signal with the 38KHz stripped?

4

Yes, all 3-pin receivers I know demodulate to data only, but 38kHz is not the only carrier frequency used.
A 36kHz receiver will work on an 38kHz signal, but with reduced sensitivity (distance).
Leo..

5

The consensus on the web is to use the IR sensor to drive an LM358 opamp to get a useable signal

The LM358 is completely hopeless for IR code signalling, it doesn't have anything like the bandwidth required. For a simple break-beam sensor it would work, but don't assume it would therefore
generalize to 40kHz signals - just a warning for people reading this and making a mental note
about LM358's and IR

6

Here's a good example of how to amplify a signal :http://www.zolalab.com.br/eletronica_projetos/ultrasonic_talk.php

This is for an ultrasound communication application but the principle on the receiver side is the same: amplify, compare and send to the arduino. Hope that helps !

7

Thanks for the replies. If I don't see a roadside TV shortly I'll order one from Banggood. They have the bare sensor dirt cheap, like <$2/10 ea.

Per this photo of a receiver board, all I need is some passives and I'm good to go.