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buffer-overflowed's Journal: Wii DIY - Wireless Sensor Bar. 4

Journal by buffer-overflowed

So, we have a projector right, which means the Wii sensor bar cable is wayyyy too short.

New cables/extenders don't come out until January. Unacceptable says I! But unlike Tycho over at Penny Arcade, I decided to do something about it. Little digging into the Wii reveals that all the Wii provides to the Sensor Bar is power. The Warnings in the manual and various info online, plus the fact that calibration picks up tungsten bulbs, means we know it's IR, and the sensor is in the Remote. A few pics of it taken apart and boom, know how it works. Junior High-School shop class level project.

So, we need a new sensor bar that's independant from the Wii, and i don't want to have to change batteries or deal with any of that, so I browse Radio Shack's online store for IR sensors. Find a 1.2V 100mA High-Power IR LED they sell. The sensor bar pics I've seen show 2 sets of 3 LEDs, seperated by a foot. So we need 6 LEDs. Our power supply needs to be able to supply 600mA. We dig around in the boxes of geekdom, where all old AC-DC converters go to rot and find a 5.7W 1000mA AC-DC Adapter. Score!

So, now it's just a question of figuring out how much resistance we need. It's an easy formula, R = (V - FV)/FC in Ohms(V is the adapter voltage, FV is the LED, FC is the mA in amps). Quick calc R = (5.7 - 1.2) / .1. 45 Ohms(and it doesn't have to be precisely 45 ohms, it just needs to be around there). So it's off to radioshack. Who only carry 10 ohm and 47 Ohm resistors. No big, nab 8 10 Ohm resistors, some PC-board, wiring, and the 6 IR LEDs. The circuit is brain dead simple, each positive/negative on the adapter, through 4 resitors each, to the LEDs in series. Solder, solder, curse at the fact that I shake, hand project off to trmj(who will have more details). Put the thing into it's case(which consists of cut pieces of a blister pack and electrical tape, sue me for non-prettyness.)

One hour later, we have a working sensor bar that actually works better than the stock one, and isn't tied to the console. Awesome. Total cost: $10.

So for anyone else complaining about this, it's not too hard to whip one up. Of course my electronics knowledge isn't so hot, but the thing barely gets warm so far(only been 3 hours though), and it works like a dream.

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Wii DIY - Wireless Sensor Bar.

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  • If you have connected the LEDs in series, and you are applying 1.2 V to each, you would need a power supply of at least 7.2V. However, if you wired them in parallel, you would be drawing 600ma at 1.2V. Therefore your resistor network would need to be R=V/I=4.5/.6=7.5 Ohms.

    From your description, it sounds like you are actually delivering about 50mA to the diodes, running them just a little above their turn-on point of roughly 0.6V.

    • They're parallel, not in series. I was tired.
    • So is that not right, I figured it as if I wanted 1.2V at 600+ma. But the last I dealt with anything EE was, oh 7 years ago, so I may have completely borked it.

      So it's parallel, + -> Resistors -> LEDs -> Resistors -> -. I'm going to redo it, I just wanted to toss a proof of concept together, so doing it properly would be nice.
  • start cranking them out and selling them on ebay. you've got until january to make some good money. i'd buy one if i owned a wii. hopefully you'd give me the slashdot discount.
     
    i watched the video that pa linked on youtube about how the sensor bar works-- pretty cool.

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