Why is Infrared (IR) Used in Remote Control?

You are so right about the ultrasound!!!

I loved going over a friends house, waiting for one of those "And the murder is..." moments, then slightly rattling my keys in my pocket. The channel would change and the whole family would flip-out!!!

Hi Electroman.

I have discovered that if I point my TV remote control towards the window with an incident angle of 45 degrees I can change channels on the TV. This seems to point to IR can be reflected from a glass surface? Am I right? Spencer.

=> Reflected by glass surface : yes

=> 45 degrees: not only that values but stated by Snellius theorm that incedent angle is the same magnitude with reflection angle. Both measured from normal line to the plane at the point of incident IR ray.

What he said.

Also it cannot be seen by the human eye

And weak IR beams have absolutely no health risks (there is still some controversy about the safety of RF signals).

IR filters can be used to minimize interference from visible light sources.

Anyone remember the mechanical ultrasonic remotes? They had a striker that would whack a metal rod that oscillated at the correct frequency. No batteries.

See my post #3...

Infra red signal transmissions are economical way and simple design approach and interface make them favourite for short distance line of sight transmission , wired hand held control , mechanical resonating remote , ultrasonic remote control , radio controls are some other types but not in use. you don`t require high power to IR remote control as they have lesser circuits for encode -decode and no interfarance problems as happens in EM radio transmission

Any one happen to get an IR reference design? Sounds useful for in-house remote control. We got so many IR controller (VCR,TV,DVD, Radio/Casset etc) at home these days.

I wrote and article for the June 2005 issue of Circuit Cellar magazine: "Short Range IR Communications System" that describes a method of diffuse reflective IR transmission that, within a room, emulates a simple RF system. It allows for signaling and data transmission with provisions for contention for "air-space" between two simultaneous transmissions. It also addresses power issues for long battery life on transmitting devices.

I also designed some of the very first IR based automatic toilet flushers that were used in commercial installations.

Several companies on the internet sell "universal remotes." Some of these require that you shoot your other remotes at it to learn what company produced the remotes.

If you want to see what your IR remote is putting out, you can see it with a digital camera or Video camera that sees through the lens. Also, you can see it with a night vision scope.

Or for a few quid you can buy a BNC connector fitted with a photodiode that you can plug into your oscilloscope, then view the signal!!

John.

I had an old Qusair (late 70's) Floor model T.V. it worked great but I had one problem with it that No one could answer. In my garage I had a Genie automatic garage door opener. IF the T.V. was on and the button pressed for the garage door, the T.V. would turn off. Never on, or change channels or anything other than turn off. Kids loved it 'cause they knew when mom and dad got home they were suppose to be doing homework and not watching T.V. so it gave them a heads up alarm. Boy did they hate it when that old T.V. died and a we bought a new one.

REMOTE CONTROLS--IR changed all the mess of "earlier radio-control"

Like Garage door suddenly opening when a particular flight comes in from NYCto land !

And IR optics in ISS enabled SEEING floods through CLOUDS/MIST above earth.