Author Topic: My Radio Shack IR Marker Wii Light Pen  (Read 9496 times)

Offline jmWii

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on: June 06, 2008, 03:20:51 PM
I made my pen with readily available radio shack parts: IR bulb, 1.5V N cell battery / holder, and momentary switch. The IR bulb sticks out of the pen, so it works great! I used string to pull down the assembly and pliers to pull up the switch out of the marker housing. Electrical tape around the bulb holds it in place with plenty of friction. I did have to trim the base of the LED to get it to fit through the marker. Johnny Lee's white board software is amazing!  :D

Jeff



« Last Edit: June 08, 2008, 11:21:46 AM by jmWii »



Offline benpaddlejones

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Reply #1 on: June 06, 2008, 08:03:30 PM
 ;D Awesome work!  ;D

Very simple!

Benpaddlejones


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


Offline Balineseterror

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Reply #2 on: June 08, 2008, 01:43:44 AM
Did you use the 276-143 (or as the package also says 276-0134 IR LED?

Also you didn't need a resistor? The LEDs I saw at radioshack had a forward voltage of only 1.2 versus the battery that is rated for 1.5

Working on putting mine together, only thing radioshack didnt have was a single battery holder so been working on finding one in the area but been wondering what to get for it + if I needed a resistor



Offline jmWii

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Reply #3 on: June 08, 2008, 11:19:34 AM
I used 276-143 100 mA nominal 1.2V IR LED with max rating of 1.6V forward voltage, so no resistor was required with a 1.5V N cell battery.

The battery holder is definitely worth it for simple changes. It fits perfectly (with just a little sanding) inside the marker.

Jeff



Offline servin

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Reply #4 on: June 15, 2008, 11:47:05 AM
thks img going to make it, is very simple  :D



Offline Francisco

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Reply #5 on: June 15, 2008, 06:37:50 PM
Servin,

If you need some more visual info, check my site here:

http://clinik.net/wiimote/wiimote_info.php

and follow the links: IR Pen1 and IR Pen2

Cheers


Offline jinzai

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Reply #6 on: June 16, 2008, 05:47:41 AM
I don't recall what the current capability of N batteries is, and all diodes can take alot of current so you could pass on the resistor when using low current batteries...but, if you look at the IR LED's parts package, you will see the current rating. (20mA, for most "normal" LEDs) I think you will get more life out of the LED and battery if you use a resistor in any case. (I = V / R) If you select a value that is near the rated value, you will not dim the output, either.

For example : .02A = 1.5V / 75 ohm

For that case a 75 Ohm resistor on either leg of the diode in series with the applied voltage should work fine.

All LED diodes that RS sells are 1.2V fwd, iirc.
« Last Edit: June 16, 2008, 05:51:50 AM by jinzai »



Offline Tweezel23

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Reply #7 on: June 17, 2008, 09:52:09 AM
Hi all. Newbie poster here. I am an ECS (computer guy) with a school system and former electronics teacher. A group of ECS's are getting together to try Johnny Lee's white board in a week or so. We are collecting all the pieces/parts now. I built a light pen last weekend to get a jump on it (attached pic-maybe, not sure it got there).

I gave some thought to including a resistor to limit current. I ended up using a AA cell with no resister, checking it with my iMac camera for operation. If you want to use a resistor, you have to take into account the forward voltage of the diode and subtract that from the battery voltage. Using jinzai's figure of 0.02A for the desired current:

R=(1.5v-1.2v)/0.02A=15 ohms

The diode has a fairly steep I vs V curve, so you can estimate the forward voltage will remain about 1.2 volts even as current changes. The battery voltage will drop slightly as current is drawn from it-the smaller the physical size of the battery, the more the voltage will drop (assuming the same type of battery here). Just guessing, I'd try a 10 ohm resistor to start and work down from there.

Thanks for the forum!