# Can Arduino IR Recievers Detect Signals from IR Flashlights?

If one has an IR reciever module similar to this and a IR flashlight like this, would the IR signal be able to be detected by the module? If not then, why?

From what I understand, these sensors don't have a particularly long range. They seem to be primarily intended for use with remotes. So, I'm not expecting to be able to do anything too fantastical here, but rather I'm simply interested in the proof of concept and/or any tinkering to make them interface better.

• If you can make the flashlight turn on / off at 38 kHz, sure. – Harry Svensson Nov 24 '17 at 7:18
• Indeed, the source must toggle at the expected frequency (often near 38 KHz). But additionally, that switched signal itself must come and go - if it is always present, most receivers will soon ignore it, as they expect the pattern to be switched on and off to signal information. So you'd likely have to modify the light with not one but two oscillators, and that may require entirely reworking its circuitry. – Chris Stratton Nov 24 '17 at 7:22

I would say: No, won't work

That's because the IR sensors like the one on the module is intended for remote control. Here's a link to a datasheet of a typical example.

Look at the table on the bottom of the first page, note how there are different types for different "carrier frequencies". This carrier frequency is the "modulation" which is used to detect the IR signal and suppress other IR sources like lights, the sun and the light from IR LEDs that are not modulated, like from an IR flashlight.

The light from the IR flashlight is not modulated but constant and will thus be ignored by such an IR sensor. It is designed that way so that they're more sensitive to the IR coming from a remote.

I have used these IR receivers with a single 5mm IR LED pulsed to $f_o$ and then gated with low data rates of 1200 baud over 30 m point to point with narrow (<10') angle emitters at rated current. I used BiPhase so the AGC was always stable.

How far do you want to go? These Rx's should easily detect a 38kHz remote control bouncing off the ceiling. ( p.s. you can use an LED backwards with -5V bias to detect current with 10k of a remote control to see if it is 38kHz up close )

If you can pulse the IR flashlight at this rate with a 10 milliohm FET switch, it should go pretty far.

• @ Tony Stewart What sunlight interference did the 30 meter links need to tolerate? – analogsystemsrf Nov 24 '17 at 16:31
• No problem from ceiling FL lamps. THe Sharp / Vishay part has a daylight blocking filter. * noted by black tint on lens * – Sunnyskyguy EE75 Nov 24 '17 at 16:37
• @analogsystemsrf A quickie measurement I made compared max_range for two cases:dark environment against daylight environment. Daylight was slightly better. – glen_geek Nov 24 '17 at 17:10