I'm looking to solve a minor nuisance with my Sony TV's remote and a cable TV providers mandatory digital adapter box -- when switching to regular cable tv i'm forced to use the digital adapter's remote to only change the channel; I dont want to use a second remote just to change the cable tv channel but instead want to continue to use my Sony TV's remote.
I saw this project and was intrigued to make some go between unit which will listen for my Sony TV's channel change IR commands then rebroadcast it in the IR language which the digital adapter understands. Such a project dealing with Arduino, soldering, and IR doo-dats is all new to me so we shall see. I'm hoping for some answers to a few questions before getting started.
I read there are 2 types of TV remote controller IR wavelengths: 940nm and 850nm. I've been able to locate 940nm transmitters and receivers but not 850nm transmitters and receivers. Can you point me to both types which would be suitable for this Arduino project with receiver modulations for 38 Khz and 57 Khz. Preferably available to Canada.
In a well lit (or dark) livingroom what distance can i expect these IR transmitter to get?
You can get the receivers from Mouser. They offer 56KHz and 57.6KHz, you'd better figure out which you need.
You will, of course, only need the 57KHz receiver temporarily, to learn the required codes from the Cisco remote. You won't need to use the 57KHz receiver in the final build.
IR receivers are not simple IR detectors, they also contain a receiver chip/circuit which is what gives them sensitivity to a certain frequency.
But IR transmitters, as far as I know, are simply IR LEDs. They don't have any particular frequency. That's up to the driver circuit, in this case the Arduino, which must be set up to produce the required frequency with one of its internal timers. The IR library normally does this all for you, but better check it supports 57KHz. EDIT: at least one library does (Adafruit) but for 57KHz the Arduino must be 16MHz, 8MHz Arduinos can do 38KHz but not much higher, apparently.
You can drive an IR led directly from an Arduino output, with only a suitable series resistor to limit the current to a safe level for the Arduino. This will work, but because of the relatively low current the output can provide, the range will be quite short. That might not matter if you can place the led close to the cable tx box's receiver. For a better range, an external driver circuit, using a transistor and other components, will be needed to boost that current up to a higher level. IR LEDs can take quite high pulsed currents (check the data sheet).
Paul__B:
but would be surprised if it made a difference.
Yes it makes a difference to the range of the remote, get the wrong one and you only have about a 3 ft range where as with the right one you will get about 6 to 10 ft range.
In a well lit (or dark) livingroom
The ambient light should make no difference because the IR is modulated and the ambient light is not. You can get the situation however when bright sunlight can saturate the receiver and so the modulated stuff can’t be detected.
I notice the Cisco box has an IR Extender socket that looks like it takes a 3.5mm stereo plug. I have no experience with extenders, but if the receiver end of the extender also does the demodulation, then maybe you could just drive that port directly from the Arduino, and not have to transmit any IR.
Also, if if you do this, the Sony will still receive the channel commands too. Will that cause a problem?
Edit: The extender won't work. If something is plugged into the extender socket, that will almost certainly disconnect the normal IR function, which would mean the Cisco remote wouldn't work anymore.