more accurate wii sensor?

Discussion in 'Wii - Hardware, Devices and Utilities' started by W.I.C.K.E.D., Mar 22, 2012.

Mar 22, 2012

more accurate wii sensor? by W.I.C.K.E.D. at 3:46 PM (2,606 Views / 0 Likes) 13 replies

  1. W.I.C.K.E.D.
    OP

    Member W.I.C.K.E.D. GBAtemp Regular

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    Would it be possible to add more IR LEDs to the sensor bar to make it more accurate? I have seen places online where people created homemade sensor bars. I just considered adding lights to the OEM bar to possibly make it better. I know power could be an issue, so if need be I could possibly use a wall outlet or even an outside usb source.
     
  2. Coto

    Member Coto GBAtemp Addict

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    I did it and the result is impressive. 40 feets away and still having good accuracy at level 2 on wiimote's light calibration. I had to remove the blackcover the sensor bar has, but I put 2 big IR leds then 3 small IR leds per side (there's 10 in total)
     
  3. W.I.C.K.E.D.
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    Member W.I.C.K.E.D. GBAtemp Regular

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    Could you break what you did down for me Coto? And what voltage were the LEDs you used?

    Edit: I just asked about the voltage because I don't know what the nintendo sensor has in it, and the point of this is to upgrade. Thanks
     
  4. Coto

    Member Coto GBAtemp Addict

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    I believe Nintendo uses 12v for sensorbar lights. But they're in serie circuitry IIRC. Because of they way those were soldered

    edit: the leds were ordinary 3v IR leds (those you record them through a videocamera and you can see them blinking), bought at like, $0.50 per unit
     
  5. W.I.C.K.E.D.
    OP

    Member W.I.C.K.E.D. GBAtemp Regular

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    So you just used any IR LEDs, didn't matter?
     
  6. Coto

    Member Coto GBAtemp Addict

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    Yeah, it doesn't matter as long as you follow the already soldered leds pattern. Well, like any led, make sure you get the + pole (positive) by looking at the bigger aluminum resistance inside the led.
     
  7. obcd

    Member obcd GBAtemp Advanced Maniac

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    While led's do have a forward voltage, the most important thing is to limit the current that flows trough them. For that reason, their usually is a resistor in serie with them.
    The continious forward current of a led usually is between 10 and 20 milli amps. By placing led's in serie, the current doesn't increase and the power loss in the serie resistor becomes lower.

    So, if you place 3 led's in serie, and they all have a forward voltage of 3V, than you will have 3*3 = 9V on the led's.

    As the supply is 12V, you will have 12V - 9V = 3V over the serie resistor.

    We want a current of 15mA, so the resistor should be 3V / 0.015A = 200 ohms
    The resistor will convert the current into heat. It's power dissipation will be 3V * 0.015A = 0.045W
    Even the smallest resistors are capable of consuming 0.25W, so, you are safely under it.

    Note that a 200 Ohm resistor will be difficult to find. 220 Ohm will probably be easier and cheaper.
    The current will be a little lower whith such a resistor. If you use 180 Ohm, it will be a little higher.
    3V / 180 Ohm = 0.016666A = 16mA
    As you can see, this is still within normal operating specifications of the ir led's.

    IR led's come in different wavelength. It might be best to have led's emitting the same wavelength as the original ones in the ir sensor bar.

    A good way to test if an ir led is working, is looking at it with a webcam or the digital cam of a cellphone. You should clearly see the ir led lighting on the picture of such device.
    You can test this with an ir remote control. If you push a button on it, you should see the ir led flashing on the cam picture.
     
  8. W.I.C.K.E.D.
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    Member W.I.C.K.E.D. GBAtemp Regular

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    So if I was to lets say...double the IR LEDs (mine has 5 currently) it would be ok by your above post as long as they were the same wavelength with a 3v forward voltage and consisting of a resistor between 180 and 220?
    I was also wondering if the wii looks for a specific number of LEDs. Like would it actually, lets say hypothetically, be better if a 42" tv had two or three full sensors to cover its width? Sounds crazy I guess but just a thought. I mean would it make it more accurate or no.

    I'm actually suprised Nintendo didn't send the system with one for above and below the tv. I would assume that it would essentially make a margin and help by letting the console know exactly where you were pointing at on the screen through calculations.
     
  9. obcd

    Member obcd GBAtemp Advanced Maniac

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    the ir detecting devices are usually designed for one specific wavelength. I have no idea which one the wii sensor bar is using.

    If you would have 5 led's in serie with a 3V forward voltage, than those would need at least 15V before any current could flow.
    So, I think the forward voltage is lower.

    I don't think the wii ir camera is looking for a specific number of led's.

    Code:
    http://letsmakerobots.com/node/7752
    
    The camera in the wiimote seems to be able to track 4 separate ir sources only.

    You could try a second motion sensor right above the normal one and see if it makes a difference. I mean, it's not like they are so expensive. Most non brand sensor bar's even have an option to insert batteries. While it's not ideal for every day use, it might be good to see if accuracy and range improve. Afterwards, you can always supply the sensor bar from a 12V adapter, or mod it so that works from the 5V supply of an usb port.
     
  10. W.I.C.K.E.D.
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    Member W.I.C.K.E.D. GBAtemp Regular

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    Ok. I bought a second sensor bar so that the wavelengths match perfectly. If I put the sensor bars side by side would that help possibly? I imagine I would have to cover the inner 5 lights on each bar when both bars are side by side (correct?). I would like to hardwire this though. I don't feel batteries. So could I just splice the wires together or would it draw too much and make each bar weaker?


    Edit: The second bar I purchased was the official....so they are both identical.
     
  11. obcd

    Member obcd GBAtemp Advanced Maniac

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    The idea of using the batteries was just to test if things worked better.
    Since your wii is only having one sensor bar connector, it could be difficult to test with 2 bars.

    I don't know if separating the ir led's further would increase the accuracy. It's kind of strange they all have the same length. If increasing that would make things better, you would expect some chinese companies that bring out longer sensor bar's. Just the extra plastic and a bit longer wires won't make it more expensive.

    If you place one above the other, it should increase the detectable range. Not sure about the accuracy.

    connecting the 2 bar's in parallel together shouldn't make them weaker. The sensor bar led's can be switched on and off, and usually the component doing the switching can only hande a limited amount of current. It might be largely over dimensionned so that it works, but without knowing which component they used, and without knowing how it sit's in the circuits, you can't tell for sure.
    The usb ports should be capable of producing 5V and 0.5Amp Even if you calculate 0.020Amp for a led, that's enough power for 25 leds.
     
  12. Coto

    Member Coto GBAtemp Addict

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    I soldered them in serie, placing bigger ones near the edges(bigger ones facing ) and the wiimote's ir camera improved both distance and side-by-side detection
     
  13. mrpinkeye

    Member mrpinkeye GBAtemp Advanced Fan

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    man, i wish i could do this. my sensor bar has trouble when im sat a few feet away! it always goes haywire and the pointer jolts all over the screen :( i do have it on a shiney black plastic tv stand under the tv, could that be effecting the sensor?!
     
  14. obcd

    Member obcd GBAtemp Advanced Maniac

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    Maybe the ir beams are reflected by the stand. You could try to place the sensor bar above your tv and see if it makes a difference.
     

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