Kerry Clendinning of the Smarter Home Club explains how IR works and offers advice on how to get better performance!
When using a device like the Harmony Hub or the Broadlink RM Pro, there are a few things you might encounter that can make automating IR-controlled devices difficult.
The first is timing. When you press a button on an IR remote, a signal is sent out, usually repeating for a short time so that the device you are controlling can have a good chance at receiving the signal, even if there are obstacles and perhaps weak batteries.
So, an IR receiver in your TV or set-top box must recognize the beginning and end of a burst of codes to distinguish one button press.
If the code being sent isn’t meant for the particular device, it will recognize that and wait for a break in time before it tries to decode the next signal.
With automated sequences sent out by a computer rather than actual human button presses, it’s possible to send two different codes so close together, a device that’s meant to receive the second code won’t be ready to recognize the beginning of a new code, because two codes were sent too close together.
Various home automation devices and programs have different ways of controlling the delay between sending out the keypress codes. Look into adding a short delay, probably a fraction of a second, if your problem seems to be related to controlling devices in a sequence.
Second, there’s something called multipath interference. You can look this up on wikipedia for a much more detailed explanation. Basically, signals from your IR remote (and RF devices, even WiFi) bounce off of anything and everything around you. Add to this that you might be using multiple IR “blasters” all sending the same signal at the same time.
So lightwaves and radio frequency waves are, as their names imply, waves. When two waves come together, due to the multiple senders or the bounced reflections, two different things might happen. Picture waves hitting one another in the water on a pond. If the crest of two waves come together, they add their collective strength, which can be a good thing in terms of IR or RF. But it’s just as likely that a crest of one wave hits the trough of another… and you get signal cancellation.
If you suspect you might have multipath interference, you can use various methods to insure that only one signal is reaching your device.
I’ve included pictures of how I used a childproofing plastic shield to block any stray signals and mount three different IR blasters (that are never active at the same time) in front of my TiVo.
Hopefully with some knowledge about these two issues, you can get your home automations running more reliably.
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