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I am fresh to the electrical engineering, and actually I am a web developer, ruby and php, etc. I am wondering that is there a simple way to control one or more LED lights using iPhone without wifi connection? I know there're already some great inventions of led bulbs, but I'd like to go in a much cheaper way, sort of like the tv controller:

I use iPhone to send certain frequency signal, and the led lights receive it and turn on or off.

Any guide will be appreciated.

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What distance must this wireless connection span? Also, what is the cost budget, and is this a one-off or a production design being planned? –  Anindo Ghosh May 16 '13 at 5:08
    
@AnindoGhosh it's enough in 20 meters. I'd like to make a one-off sample first, so should lower the cost as much as possible, best less than $5. will see to make a production design in the future :) –  Jinzhao Huo May 16 '13 at 5:47
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At less than $5 for a one-off, there don't seem to be any evident options. At best, an IR LED might be worth exploring, if it can be driven from the audio jack - extremely unlikely that the headphone port can support the currents needed by an IR LED, though. Just out of curiosity, how much did the iPhone cost, in contrast to the prototyping budget of $5? –  Anindo Ghosh May 16 '13 at 5:55
    
@AnindoGhosh Thanks, I'll try exploring IR LED first. Do you know how much the wifi version might cost? –  Jinzhao Huo May 16 '13 at 6:03
    
@AnindoGhosh if possible, I wanna make a widely used product in daily life, so a $50 like product is kind of too pricy. Better to control it at most $10 or even less, especially for those non-dollar countries :) –  Jinzhao Huo May 16 '13 at 8:54
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2 Answers 2

If you don't want to use Wifi or Bluetooth and it turns out you can't drive an IR LED with the audio jack or another inexpensive means, then you'll probably have to use audio.

The LEDs you wish to control can be differentiated by building each with a simple, very low cost, band-pass filter tuned to a particular audio tone. The iPhone can emmitt the proper tones that the LEDs respond to. It's not a sexy idea, but it's likely to be one of the lowest cost options available.

This is, by the way, how some of the very first TV remotes worked (though they used ultrasound, and I'm not sure you'll convince the iPhone to do that).

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+1 for an unconventional suggestion: There is a patented technology called Near Sound Data Transfer (NSDT) that does precisely this, and can be made to work on practically any smartphone. Range of 20 meters is next to impossible though. –  Anindo Ghosh May 16 '13 at 6:48
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The iPhone has Bluetooth, so you could always build a Bluetooth transceiver into your "thing" in order to receive control information from the iPhone. You would likely need a microprocessor of some sort to interface with the Bluetooth transceiver and control your LEDs.

The other option is to build some custom hardware that can interface with the iPhone using either Bluetooth or USB, which would allow you to use any communication scheme you can dream up to communicate with the "thing".

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Thanks, Amoch. USB is not a good option, cuz wireless is a must :) I thought about bluetooth before, just worrying about the same reason as wifi, cost –  Jinzhao Huo May 16 '13 at 3:18
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The USB option was meant to provide an interface to a "dongle" type device that is attached to the iPhone and contains whatever wireless transceiver you wish. In this way you could use another wireless technology like infra-red, zigbee, etc even though the iPhone is not able to support these technologies directly. –  Amoch May 16 '13 at 3:56
    
I see it, thanks for the explanation. –  Jinzhao Huo May 16 '13 at 6:05
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