ir sensor identification

Thread Starter

dansteely

Joined Feb 26, 2017
37
Hi All,

I use small 44 key remote controls & receivers for controlling RGB LED strings.
I'd link to identify what kind of IR receiver they are so I can order some separately for experimentation.
Looking on my local suppliers website I note that they are available using different carrier frequencies (56/50/38 & 36 kHz)

Using a scope, how can I identify the frequency of my LED string controller?

Many thanks.
 

Thread Starter

dansteely

Joined Feb 26, 2017
37
Thanks both. I've worked out that it's a 38kHz (TSOP4138 equivalent)

On the scope, when I capture the waveform (sorry no screen grab or measurements to hand) there is a long pulse followed by a much shorter one.

No mater which button I press on the remote control the waveform appears the same.
Using on-screen calipers, the waveform durations measure the same.

What am I missing?
 

Bernard

Joined Aug 7, 2008
5,773
The output from the TSOP4138 has already been demodulated, might go back to transmitter or
use a photo transistor as an emitter follower. Will need IR wavelength to select IR sensor.
950 nm.
 
Last edited:

Thread Starter

dansteely

Joined Feb 26, 2017
37
As with everything in electronics & life, the more you look the more you see.

It's got my interest going and i've got a few photo diodes (SFH213) in my CPC shopping basket so I can see the raw data vs the demodulated output.

EEVBlog Dave did an interesting video covering this stuff. Link

Many thanks for your help.
 
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