#15273 - 03/02/06 10:16 AM
Build an infrared (IR) blaster
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Guy Lavoie
Beyond All Hope
Registered: 12/21/02
Posts: 5821
Loc: Montreal, QC, Canada
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The IR output on a Ocelot/Leopard is designed to be used with stick-on emitters such as the ones made by Xantech. These need to be stuck right over the TV's (or whatever device you're controlling) IR receiver window. In many installations, you might want to have a high power IR transmitter (often called a "blaster") located somewhere in front of the device(s) that you want to control so that the commands can be sent just as if you were using a handheld remote from a distance.
The Ocelot or Leopard is driving the infrared (IR) emitter in a low power fashion using a pullup circuit through a current limiting resistor to drive the IR LED directly. All you need is a small amplifier circuit to drive a regular IR LED at high power in order to send ("blast") IR across a room. IR LEDs ( and any LED for that matter ) can be driven at relatively high currents if the duty cycle is very short. The IR LED I used here is rated for about 20 mA if ON continuously, but can be driven with about 1.2 A (yes, that's amps )when pulsed for microseconds at a time as is done in remote control protocols.
Examine the schematic diagram below. The IR LED I used is a Radio Shack cat # 276-143C, but pretty well any IR LED should do. One important thing to note: Use a seperate 12V dc power supply for the circuit, do not try to use the same power supply as the Ocelot or Leopard! This is because the controller's power input goes through a bridge rectifier internally, so you do not have the same common ground on the external IR jack. Use an isolated wall transformer (wall wart) with a 12v dc output. The 2N3904 transistor can probably be substituted by any general purpose NPN switching transistor, like a 2N2222. Another advantage with this circuit is that you can drive several IR LEDs simultaneously by replicating the circuit for additional LEDs. I have two IR LEDs in two rooms (I first verified that the IR codes for one TV were ignored by the other one; it helps if both TVs are of different brands). If you make more than one circuit, simply wire them to the same mini phone plug that goes to the Ocelot. The 12V power supply is shared by all circuits.
Note: you might not be able to find 15 ohm resistors at places like Radio Shack. In that case, you can create and equivalent circuit using more commonly available 10 ohm resistors, as shown in the diagram.
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#15274 - 04/09/06 07:01 PM
Re: Build an infrared (IR) blaster
[Re: Guy Lavoie]
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Barryfive
junior
Registered: 02/01/03
Posts: 38
Loc: Arizona
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Wouldn't it be as just as easy to use an amplified block such as Niles or Xantech make and amplify the signal? You could then use multiple IR emitters.
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#15278 - 05/19/06 05:39 AM
Re: Build an infrared (IR) blaster
[Re: Guy Lavoie]
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Matz Hedman_dup1
newbie
Registered: 05/10/03
Posts: 8
Loc: Stockholm
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Gemini
I have built the blaster according to Guy's layout powering it with a 9V battery. It has been running on the same battery for 3 years now and still alive and kicking.
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#15280 - 01/02/07 06:02 PM
Re: Build an infrared (IR) blaster
[Re: Gemini]
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Todd R.
active contributor
Registered: 05/27/03
Posts: 178
Loc: CA
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Guy,
Could I use this circuit for a Xantech Hidden Link receiver output, which is 12vdc?
I assume you could tap off the output, which currently goes to a Xantech IR hub, and drive this blaster as well.
I need to turn a corner and blast a Russound A-Bus keypad that has an IR receiver!
Thanks
_________________________
Todd Reed
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#15282 - 03/18/07 07:21 PM
Re: Build an infrared (IR) blaster
[Re: Guy Lavoie]
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sash18
journeyman
Registered: 08/31/05
Posts: 61
Loc: Melbourne
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Ok, well I tried to biuld one of these over the weekend and it didnt work. I used parts from Jaycar (Aust. Radio Shack equivilent).
I'm thinking I might have the resistors around the wrong way. Can you describe exactly which way these need to go (i.e. the coloured rings on the resistor in relation to which way the line is headed - the phone plug-transistor & IR LED). Sorry to be a pain, but I'm no electronics genious but can use a solderin iron effectively enough.
Also, I have a Marmitek IR repeater pyramid thingies that can take IR from one point and transfer it to another room via RF and then back to IR again.
My question here is 'Will this IR blaster be more effetive than the device I currently have?' Reason I ask is because I have the LEO 2 connected and the little IR emitter mouse thingy pointing directly at the pyramid and its not so good with IR, like the LEO 2 makes the IR happen and the pyramid works sometimes and not others. I want a better solution so I'm hoping this thing is powerful enough to be more consistent.
Cheer's
Sash
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#15284 - 03/18/07 08:04 PM
Re: Build an infrared (IR) blaster
[Re: Guy Lavoie]
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sash18
journeyman
Registered: 08/31/05
Posts: 61
Loc: Melbourne
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I have the emitter in that little section of the powermid. It does work through the LEO 2, but not as consistently as say if you were to point the remote at the powermid and push the button. Does this sound like an IR learning issue or something to do with the set-up? Ideally, the IR blaster would be better as it cuts out the RF bit and blasts it directly. Plus its easier to hide than the powermid. I'll post some pictures when I get home (be warned though, its pretty dodgy looking at the moment....lol).
One more question though, Point B on the diagram is connected to the middle prong coming out of the transistor right? If not, then I've got it wrong. I only ask becasue it looks a little like it may be the end prong and not the middle.
Cheer's
Sash
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#15286 - 03/19/07 08:57 AM
Re: Build an infrared (IR) blaster
[Re: Guy Lavoie]
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Dowser
journeyman
Registered: 12/04/06
Posts: 73
Loc: Sweden
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Would it be possible to have multiple parallel IR-diodes without modifying that design?
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#15288 - 03/20/07 04:26 AM
Re: Build an infrared (IR) blaster
[Re: Guy Lavoie]
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sash18
journeyman
Registered: 08/31/05
Posts: 61
Loc: Melbourne
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Ok, its still not working. I have everything connected like your diagram and its a no go. This is quite a shame as I would rather use this than the powermid thingy's I'm currently using. This will be much easier to hide across the room than a pyramid looking thing. I've attached photo's. Now please dont laugh at the stupid way I did it. I didnt have a PCB so I just joined everything as required. I'm spewing it doesnt work.
Picture; (Sorry they came out blurry - phone camera)
Cheer's
Sash
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#15290 - 03/20/07 02:38 PM
Re: Build an infrared (IR) blaster
[Re: Guy Lavoie]
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sash18
journeyman
Registered: 08/31/05
Posts: 61
Loc: Melbourne
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Ok, I'll use the digital camera tonight and take some better pictures. i dont have anyone that is an electronics guru so I'll have to do in this case....
Cheer's
Sash
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#15291 - 03/24/07 05:13 PM
Re: Build an infrared (IR) blaster
[Re: sash18]
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sash18
journeyman
Registered: 08/31/05
Posts: 61
Loc: Melbourne
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Not sure where it went wrong, but this thing started to work on its own without my help. It actually work quite well when its pointed in the right direction of course.
It certainly beats the alternative of using the powermids and stick on emitter. This is much easier to conceal and you can run the IR LED line pretty fat, I've put 2.5 meters on mine and it seems to work fine.
Thanks for this, it was pretty easy to make. Oh yeah, I'm running it on a 9V battery, I'll tell you how long it lasts.
Cheer's
Sash
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#15292 - 03/30/07 12:07 AM
Re: Build an infrared (IR) blaster
[Re: sash18]
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sash18
journeyman
Registered: 08/31/05
Posts: 61
Loc: Melbourne
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Quote:
I think that some people have done that with 2, maybe 3 diodes. If the goal is to get more signal strength, you might want to use 2 or 3 diodes and reduce the 15 ohm resistor to 8 or 10 ohms. It is best to get identical IR LEDs if you want to try this.
I'd actually like to try this to increase reliability and point them at the entertainment centre from across the room at a few different angles (3 - Centre, Left and Right). Guy, do you think you could modify your above pic to show how you would do this in parallel? Even if you just roughly pencil in where you would splice the wires into.
Cheer's
Sash
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