Gamecube screen LED mod

Psy · Post by **Psy** » Tue Jan 11, 2005 8:12 pm

Is there a way to replace the lighting tube from a 4Gamers cube screen with LED's? I have removed the tube and it's casing and it has literally halved the weight, plus I'll be able to compress it so it takes up less space. How many LED's and what type would I need and what ohm resistor would I need to put in front of them?

HK-47 · Post by **HK-47** » Tue Jan 11, 2005 8:20 pm

Look on doomportables under screens...

Psy · Post by **Psy** » Tue Jan 11, 2005 8:45 pm

Thanks HK, but what ohm resistor would I need to attach it to 12V?

HK-47 · Post by **HK-47** » Tue Jan 11, 2005 8:49 pm

Theres a formula on the bottom of the page where it shows you the psone lcd mods... Look there...
Heres a quote:

If they're 5mm LEDs (T-1_3/4), return them. Get 3mm (T-1) ones from Digikey or Mouser. 5mm ones won't fit at all in the Sony screen. Trust me.

Ben says to hook them up in parallel, doomportables says in series. I say parallel; that way you're sure they have enough voltage. Remember, there's a nominal 3.6V drop (or whatever; it's a spec on the LED you choose) across each. Put a resistor in series with the (parallel) LEDs. Use the equation

R = (Vs - Vf)/I,

where R is the resistor value, Vs is supply voltage, Vf is forward voltage (LED spec), and I is the desired current. Try a couple different values for the resistor, up to the max current for the LEDs. Remember, the current from that equation is total current for the 3 LEDs. Use the 7.2V supply, not the cathode power supply.

G-force · Post by **G-force** » Tue Jan 11, 2005 8:51 pm

Instead of a resistor you could use the voltage off a regulator on the GC screen. Or a separate regulator from www.mouser.com
I would use two 5mm LEDs, one at each side of the screen. You could get nice even lighting this way. I did this to a Interact ps1 screen and it worked great.

Psy · Post by **Psy** » Tue Jan 11, 2005 9:05 pm

So for this LED ( http://www.maplin.co.uk/Module.aspx?Mod ... 3&doy=12m1 ) that would be: R = (Vs - Vf)/I

Vs = 11.7
Vf = 4
I = 30

So:

R = (11.7 - 4)/30

R = 7.7/30

R = .26

So would that mean a 26ohm Resistor? Please tell me if I'm out on my calculations, or if I'm using the wrong figures.

Post by **gannon** » Tue Jan 11, 2005 9:13 pm

I think that'd be a 260Ohm resistor

Psy · Post by **Psy** » Tue Jan 11, 2005 9:27 pm

Where would I be able to order one?

A.J. Franzman · Post by **A.J. Franzman** » Wed Jan 19, 2005 4:38 pm

Psy wrote:So for this LED ( http://www.maplin.co.uk/Module.aspx?Mod ... 3&doy=12m1 ) that would be: R = (Vs - Vf)/I

Vs = 11.7
Vf = 4
I = 30

So:

R = (11.7 - 4)/30

R = 7.7/30

R = .26

So would that mean a 26ohm Resistor? Please tell me if I'm out on my calculations, or if I'm using the wrong figures.

Close, but for R to be in ohms, I needs to be in amps, not milliamps (divide mA by 1000 to get amps). So:

R = 7.7 / 0.03
= 256.7

or about 260 ohms. Closest standard values are 220 ohms (too much current, may shorten your LED lifetime drastically) and 270 ohms (slightly dimmer, but I bet you wouldn't notice the difference). If you want to salvage a resistor, look for one with stripes:
red-violet-brown-gold

Post by **Gamelver** » Wed Jan 19, 2005 4:57 pm

you could just get a 220 ohm resistor, and then wire 4 ten ohm resistors in series (or any other combination of resistors to get 40 ohms.....). That's basically what I did for my psone screen led mod, I didn't have the right amount of ohms, however by adding certain resistors in series I got pretty close

.

A.J. Franzman · Post by **A.J. Franzman** » Wed Jan 19, 2005 7:32 pm

Gamelver wrote:you could just get a 220 ohm resistor, and then wire 4 ten ohm resistors in series (or any other combination of resistors to get 40 ohms.....).

This is not even remotely worth the trouble - did you even measure the resistance after you made this chain? Standard resistors are 5% tolerance (the meaning of the gold band). For 270 ohms, this is + or - 13.5 ohms - so if you have a bunch of 270s from different sources (not all one batch from the same production run), there's a very good chance one of them is close to 260 (remember the actual calculation was 256.66666 ..., so if you really want to mickey mouse it, try something like 220 plus 33 or 39 to get closer.)

Again, a current difference the range of 5% - 10% is really not noticeable. Don't believe me? Grab a handful of matching LEDs and 5% resistors, and hook them all up to a supply that can handle the current - 1 resistor in series with each LED, and all LED/resistor pairs in parallel. Notice any major differences in brightness? No? Now shut it down, disconnect, and measure the actual resistance of all the resistors. Are they all exactly the same? Not even close!

HK-47 · Post by **HK-47** » Thu Jan 20, 2005 2:30 pm

Im not taking any electronics classes (I dont get science till feb.

) but isnt there a thing where you can wire two resistors in parralel for half the resistance or something? (Ex two 500 ohm resistors in parralel are 250 ohm? ) I have no clue, but I vaguely remember something along the lines of this.

Post by **SpongeBuell** » Thu Jan 20, 2005 2:59 pm

yes, they would be cut in half only if they are the same value. Or you could have 3 for 1/3. The equation is this, if you are interested:

R=1/[(1/R1)+(1/R2)] for as many resistors as you want

HK-47 · Post by **HK-47** » Thu Jan 20, 2005 3:19 pm

SpongeBuell wrote:yes, they would be cut in half only if they are the same value. Or you could have 3 for 1/3. The equation is this, if you are interested:

R=1/[(1/R1)+(1/R2)] for as many resistors as you want

Cool. I barly remembered something and I got it right! Yess! So I guess you could go this way also. It would give you 250 instead of 256, but I think its close enough.

A.J. Franzman · Post by **A.J. Franzman** » Thu Jan 20, 2005 3:44 pm

Wrong again - it would be even closer! 500 ohms is not a standard value, but 510 is. Two of those in parallel = 255 ohms. Taking tolerance into account, this combo could end up anywhere between 242.5 and 267.5 ohms, but the averaging effect of having resistors in parallel means it's more likely to be closer to 255.

This is borderline as far as whether it's worth the extra resistor to put the current right at the LED's limit, vs. having one less resistor and a tiny fraction less current (using one 270 ohm resistor). Personally, I would still just drop in a 270 - the difference in brightness is still negligible, and there's much better chance of getting a long life out of the LED.