Mk120 IR Light Barrier how to adjust sensitivity

Kits Mini Kits Range
1

Hi,

is there a resistor I can replace with a potentiometer to adjust the sensitivity of this IR beam break alarm? :question:
(MK120 Beam Break Kit)

Schematic is here:
http://www.velleman.eu/downloads/files/schema/receiver.jpg

thanks

2

Kit ‘as-is’ is at maximum sensitivity.
You could increase the the series resistor of the IR leds to reduce sensitivity.
Sorry, no values, please experiment.

3

ok, another question, why are there two IR leds in the transmiter instead of just one?

4

More leds = more power.

5

is the IR output modulated? If so, what freq?
and does the detector look for this?

6

yes, it is modulated (see schematic diagram).
freq: a couple of kHz (this has not been measured).
At the receiver end, the signal is filtered.