Infrared question

[FJ and G]

Ordered K-Line's IR/battery/R/C set. However, a friend told me the other day that IR doesn't work well outside (where I intend to run the set).

Can anyone advise? Isn't IR how controls are done for R/C cars, planes, boats, etc?

Much thanks!

[cnw1995]

I ran the K-Line set outside successfully with IR but it wasn't in direct sun. I'll have to try it out when the sun comes out again.

[FJ and G]

Thanks Doug,

Night ops would be fun as well, as my future set has passenger/caboose lighting. All that must be a drain on the D-cells.

Wondering if they make rechargers for D-cells. Know they do for AA and AAA.

[lionelsoni]

"R/C" stands for "radio controlled".

Infrared photodiode detectors don't work well in sunlight. Their noise increases with the DC current; and sunlight makes a lot of DC current. Even with very narrow-band optical filters, sunlight is a problem.

[FJ and G]

Thanks, Bob,

How then do model airplane/cars/trucks get away with using R/C and would you know of a modification that could be performed?

(I'm thinking if not then could operate on overcast day or in evening)

[csxt30]

Dave: I don't recall much IR being used in R/C. Maybe for the Giros or tach, but I can't even remember it used in them, now.
Also, you should be able to make up or buy any type battery pack & get a charger for it.
Check out Tower Hobbies, & their chargers. Mr. Duda can advise you well on that Dept!

[otftch]

On our club layout everything works fine until we open the back door of the shop.Then our IR equipped accesories go nuts.Close the door and everything's fine again. It really had us going the first time it happenned.We were tracing wires and looking for mistakes,for hours.
Ed

[fwright]

The sun puts out lots of IR radiation which tends to overwhelm our puny transmitters and receivers. IR is really just another radio frequency, only just below the visible light band. It is very cheap to make IR transmitters (an LED) and receivers (photo detector). Fancy modulation schemes and coherent frequency generators are not needed - you just turn the LED on and off in a code pattern. But without a specific modulation scheme and coherent frequency generator there is no way to dig into ambient noise for the signal. And the sun's IR radiation provides lots of ambient noise!

Radio control uses much more sophisticated transmitters and receivers, and uses a frequency where the sun does not produce much radiation. All these factors lead to better performance outdoors.

yours in signal processing

[lionelsoni]

Fred, the dominant noise produced by sunlight in a photodiode comes not particularly from the infrafed component of the sunlight but from the shot noise, the noise made by the random motions of the individual charge carriers that carry the DC current produced by the entire spectrum that the detector is sensitive to. This leads to the usual strategy of filtering out all optical frequencies except those needed for the very narrow-band infrared signal. The best filters use an interference principle, which involves a tradeoff between bandwidth and viewing angle, since the center frequency of the filter shifts with the angle from the perpendicular.

This is probably more than anyone wanted to know.

[FJ and G]

thanks guys. I'll do more moonlight running (hopefully the moonbeams don't do anything other than bring out the vampires) [:D]

[Anonymous]

I'm not sure what IR has to do with RC. It was my impression that the K-Line battery set is IR, period. Joe

[Jim Duda]

I suppose you could convert one of these sets to true R/C fairly cheaply if you just wanted forward-neutral-reverse with no sound by purchasing a cheap 2 channel system ($30-$40) and an ESC (electronic speed controller) that has Fwd-Rev capability and can handle the amp draw of the motor(s). You would connect the ESC into the throttle channel and wouldn't use the servo in the 2nd channel. Connect the ESC power leads directly to your motor(s). It will vary the speed, stop the motor(s) and reverse them, depending on the position of your transmitter stick or trigger.

R/C car/truck battery packs are cheap and depending on the mah rating of the packs, could give you run times in hours, and could be placed in a suitably sized boxcar.

Be sure and get your radio system on a SURFACE frequency (75 Mhz band) so you don't shoot down any aircraft!