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Topic: Controlling IR blaster box with arduino (Read 2 times) previous topic - next topic


Trying to make an IR blaster to control some toys. I've got working code that will drive an IR LED and it works, but I wanna up the power significantly. I was looking for something else and found an older RF-IR box from an old remote control. Don't even have the remote any more, so I opened it up. Looks like I should be able to hack it to control the LEDs via my arduino, but wanna make sure I'm not going to fry anything here (not an expert by any stretch of the imagination - I know just enough here to know I need to ask the experts!)

Here's the board in the IR blaster (much bigger pics if you click on them, but they're still just cell phone pics so not the greatest):

IR front by mostlytechnic, on Flickr

IR back by mostlytechnic, on Flickr

Obviously the top right (of the lower pic) is the transformer (runs off normal AC, not a wall wart) and in the very corner is a jack for an external IR blaster.
Across the bottom are the 4 IR LEDs, a red LED for showing the signal, Q6 (just left of center at the bottom) is the transistor driving the LEDs, and a couple resistors (one's between the microprocessor and the transistor; one's in series with the LEDs).

On the other side (top pic) there's the RF section under the metal shield (which I don't care about), a processor in the center (also don't care about), and other stuff.

So, tell me if I'm following this right. The center pin on the right hand side of the main chip goes off to R21, which then goes over to the center pin of the transistor (sorry, don't have the board with me right now to get the numbers off the transistor to see exactly what it is). Looking from the green side of the board, the right leg of the transistor goes to the huge trace, which I assume is ground? The left leg goes to R20 and then off to the LEDs.

So, here's my questions (again, don't have the board here to start checking stuff with a multimeter)...

1. To use an arduino to control the LEDs, I'd connect the output pin to R21? Or more likely, see what voltages this things running at R21 and possibly go output-new resistor-transistor? And then connect ground from the arduino to somewhere....

2. What's all that going on near the transformer? I see 4 diodes? on the brown side and small caps on the green side, plus a bigger cap and another transistor? (U1) on the brown side - all where the blue power wires from the transformer connect. Is that power stabilization? Voltage regulation? Something else?

3. I'll check the voltage coming out of the transformer - assuming it's in an ok range, any reason not to power the arduino off it?


Ok, had a few minutes to play with it...

1. Noticed that under the blue wires from the transformer it's labeled 12VAC. The component labeled U1 (next to the biggest cap) is a 78L05 voltage regulator. So all the diodes and stuff there is converting the AC to DC, and then the VR is dropping it from 12 to 5, right?

2. I did stick a multimeter on the output of the voltage regulator. It's giving a nice 5.05V and I saw about 90ma between it and ground. That's not powering any LEDs or anything at that point though.

So, I'm guessing I shouldn't power the arduino (probably a teensy) off that voltage regulator. What powering THIS off the same power source as the teensy (probably a basic AC to USB adapter)? Just bypass the all the power regulation stuff on this board completely. Thoughts?



Hooked up the arduino to the IR box, and it's working great.

Connection I used was to hook a PWM pin to R21 and ground to ground. Plugged in the IR blaster and started the program on the arduino - worked perfectly. Got lots more range than the old IR LED setup I had.


Interesting idea and project, thanks for sharing.

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