Comments on: Building a Wii “Sensor” Bar project

By: eyeonthewinner

eyeonthewinner — Sun, 07 Jun 2009 18:06:21 +0000

Nice work, i’m gonna make mine right away!!

By: prince

prince — Mon, 30 Mar 2009 18:05:00 +0000

i appreciate your work

By: EagleEyed

EagleEyed — Fri, 19 Dec 2008 13:52:17 +0000

I think Thuan meant
(Vsource – Vled_drop ) = (5V – 3 * 1.4V) = 0.8V
seeing from the spec that the LEDs are rated at 1.4V

By: JXABC

JXABC — Thu, 01 May 2008 07:11:06 +0000

Hmm. Doesn’t the math work out to be (5-3*1.2)=1.4 volts, therefore 1.4/.05= 28 ohms?

By: Thuan

Thuan — Sat, 08 Dec 2007 15:16:54 +0000

Yes. I’ve been able to get it to work as far as metres and beyond.

By: Martin Zwigl

Martin Zwigl — Sat, 08 Dec 2007 10:43:46 +0000

Thanks for answering.

I used the same calculation and got the same result with the 16 ohms.
Do you still get enough output power on the LEDs for the controller.
That’s, why I’ve been asking. (Well I asume so, since you wouldn’t have posted it elsewise)

Cheers, from Austria

By: Thuan

Thuan — Fri, 07 Dec 2007 07:14:14 +0000

Hi Martin,

You’re comment has reached me. I’m not sure how you got that calculation – can you provide some steps as to how you got that? In any case, you’ve asked a good question because I also stumbled upon something similar to this.

When dealing with LED circuits, one should use this formula as mentioned in Wikipedia (http://en.wikipedia.org/wiki/LED_circuit):

R = (Vsource – Vled_drop) / Iled

In my case, (Vsource – Vled_drop ) = (5V – 3 * 1.2V) = 0.8V and Iled = 0.05 A (should be measured in amperes) for each string of LEDs. This will get you R = 16 ohms, but the electronics store that I bought the resistors from didn’t carry 16 ohms resisters if I remember correctly. The next resistor step up that they had were 18 ohms, and using those is generally a little safer than something less than 16 since it provides sufficient resistance to power the LEDs.

By: Martin Zwigl

Martin Zwigl — Thu, 06 Dec 2007 22:16:06 +0000

Hi there.

Seems that my comment yesterday has not reached you. So I’ll ask again.
I am a newbie at electronics. What is this with the 50mA on the LEDs and the 18 ohms resistors. My calculation shows that if one puts in 18 ohms resistors that leaves just 44mA on the LEDs. Is this on purpose?

Thanks for clarifying.
Martin

By: Martin Zwigl

Martin Zwigl — Wed, 05 Dec 2007 23:38:59 +0000

Hi there

50mA on the LEDs. On the other hand 18 ohms resitors. Doesn’t that bring it down to 44mA.
Am I missing something?

Greetings from Austria,
Martin