So, my next move will be changing that IR sensor and installing the leds (link below) -> solder them (2) in series with aprox 17ohm reistor and power them from the 5V pin, through a transistor which will be controlled by "IR ledpin".
Lets see if it it going to work better this way...
leds:
Are you going to use a logic level mosfet or NPN transistor.
An NPN transistor also has some dropout voltage.
Calculate 0.5volt for e.g. a 2N2222 with 470ohm base resistor.
In that case your CL resistor should be 12ohm.
Leo..
So like this?
No.
Emitter to Arduino ground.
470ohm resistor between Arduino pin and base.
String of "resistor and two LEDs" between 5volt and collector.
Fifth image on this page.
Leo..
Can it be like this then?
I need to have transistor as close as possible to the board. Leds are far away (on 7m cable).
wvmarle:
Or you have to use a PNP transistor, like this:
That's an NPN transistor used as emitter follower.
Dropout voltage is higher than grounded emitter, and could be too much for two IR LEDs in series.
The circuit I suggested should work when the LEDs are at the end of a 7meter wire.
Just leave the 12ohm resistor and the transistor near the Arduino.
Post a diagram, so we can check.
Leo..
Mmm... I should look more carefully at the Google search results as I did ask for PNP high side 
Wawa:
Post a diagram, so we can check.
Leo..
So like this?
JohnyStone:
So like this?
Yes!
Karma for the real (not Fritzing) drawing.
Leo..
OK. I'm going to buy all I need and try to make it work.
One more thing:
The reciever will be connected on the 5V and GND aswell (without any resistor).
I hope it is not a problem.
