Poll

poll? what poll? why?

I just wanna post to the forum
0 (0%)
weird.
0 (0%)

Total Members Voted: 0

Author Topic: IR LED Power question  (Read 8411 times)

Offline wiimotacular

  • *
  • Posts: 2
  • Karma: +0/-0
    • View Profile
on: April 26, 2008, 03:57:32 PM
I'm having trouble getting the Wiimote to see my IR LED in Johnny's configuration (See http://www.cs.cmu.edu/~johnny/projects/wii/pen.jpg).  It only sees the light when it is pointed directly at the camera at about an inch or so away or closer.  More than an inch away and anything less than straight on and the IR visibility numbers disappear.

Here are the parts I'm using.

New AA Battery
Radio Shack 270-401A battery holder
Radio Shack 276-0143 IR LED with the following specs:
   Absolute maximum ratings (25 deg C)
      Forward voltage (20ma):   1.6V
      Reverse voltage:          5V
      Reverse current:          10uA
      Wavelength:               940nm

   Electric characteristics (25 deg C)
      Radiant power output (100ma):   16mW min.
      Forward voltage:                1.2V
      Forward current:                100mA
      Viewing angle to 1/2 intensity: 45 deg

I haven't yet implemented the switch because I wanted to test whether the light was strong enough in the first place.  Apparently it's not (or there's something wrong with the Wiimote...but it does work fine with the actual Wii).

Can anybody help me here?  I've gotta have a better excuse for why was messing with this stuff and therefore didn't fix the bathroom sink today. ;)

Thanks.




Offline imarzouka

  • *
  • Posts: 13
  • Karma: +0/-0
    • View Profile
    • LED Calculator
Reply #1 on: April 26, 2008, 04:41:46 PM
Radioshack IR LEDs are not so good. Tried one myself and it was also too low. If you have a digital camera, try putting the IR LED next to a TV Remote and see how good is it. Usually TV remotes are good enough.

Let me know what happens. Good luck :)

Iyad Marzouka
http://ledcalculator.net



Offline wiimotacular

  • *
  • Posts: 2
  • Karma: +0/-0
    • View Profile
Reply #2 on: April 26, 2008, 06:21:01 PM
Yeah, when I tried using a DVD/VHS combo remote with the Wiimote, I had fewer problems with the range...except that the remote blinks causing erratic behaviors onscreen.

What IR LED do you recommend?



Offline inio

  • Wiki Admin
  • *
  • Posts: 124
  • Karma: +5/-0
    • View Profile
    • my Wii Remote projects
Reply #3 on: April 27, 2008, 03:29:56 PM
New AA Battery
...
Forward voltage (20ma):   1.6V

If your specs are correct, and your battery is fully charged, you'll be getting significantly less than 20mA, more like 2ma probably (LEDs are, like diodes, highly non-linear).  Try using two batteries and ... (assuming 1.4V nominal for the batteries):

V = I*R
R=V/I=(2.8V-1.6V)/(100mA) = 12 ohms

... a 12-ohm resistor.  Or 14 ohms if you want to be safe (assume perfect batteries).

Also, 850nm LEDs are detected at about twice the intensity as 950 for a given current.
« Last Edit: April 27, 2008, 03:31:37 PM by inio »



Offline maarten

  • *
  • Posts: 1
  • Karma: +0/-0
    • View Profile
Reply #4 on: May 03, 2008, 08:28:08 AM
Also, 850nm LEDs are detected at about twice the intensity as 950 for a given current.

Wasn't it the other way around?



Offline benpaddlejones

  • Support Admin
  • *
  • Posts: 1178
  • Karma: +49/-0
    • View Profile
    • Inter.Connect.Ed
Reply #5 on: May 10, 2008, 09:04:34 PM
wiimotacular

I concur! Under powered and no resistor (can't comment on quality of Radioshack IR-LED, not available in Australia)

Read: http://www.wiimoteproject.com/ir-pens/electronics-101-sharing-my-mistakes-updated-t834.0.html

Will help you understand inio's comment and calculate for yourself

benpaddlejones


See my full profile and links on my Google Profile: http://www.google.com/profiles/benpaddlejones