Casio EV-680 led mod

nos_slived · Post by **nos_slived** » Sat Apr 23, 2005 11:28 pm

You realize that the cheapest on that link is $2, and that is only 5000mcd. 16000mcd is extremely bright, and would make it hard to see anything other than the LED.

goodie · Post by **goodie** » Mon Apr 25, 2005 7:54 pm

I just bought these ones. If nothing else, that sure beats Digikey's prices. (especially with their dumb service fee and all.) Now I won't have to worry about running out of LEDs anytime soon!

goodie · Post by **goodie** » Tue May 03, 2005 3:30 pm

Okay, I got the LEDs in today. I will be having two of them in parallel. What value of resistor(s) would I need to drop 5 volts to the 3.3 volts that the LEDs use?

Another question: The page said the LEDs have a reverse voltage of 5.0v. What does that mean?

*o* · Post by ***o*** » Tue May 03, 2005 3:33 pm

should i get 3 5000mcd leds for a psone screen?

nos_slived · Post by **nos_slived** » Tue May 03, 2005 5:40 pm

goodie wrote:Okay, I got the LEDs in today. I will be having two of them in parallel. What value of resistor(s) would I need to drop 5 volts to the 3.3 volts that the LEDs use?

Another question: The page said the LEDs have a reverse voltage of 5.0v. What does that mean?

Can't say unless you tell us the highest possible current.
Use the formula:
R=(Vs-Vf)/I
R is value. (Vs-Vf) is the voltage supplied minus voltage needed. I is maximum current.

HEY! I just realized that I had a test on this stuff in science today.

As for reversable 5V, I'm not sure, but my best guess is that it can handle up(down, I guess) to -5V.

goodie · Post by **goodie** » Tue May 03, 2005 5:51 pm

nos_slived wrote:Can't say unless you tell us the highest possible current.
Use the formula:
R=V/I
R is value. V is the voltage required (3.3 for you). I is maximum current.

HEY! I just realized that I had a test on this stuff in science today.

As for reversable 5V, I'm not sure, but my best guess is that it can handle up(down, I guess) to -5V.

Does this help? Sorry, I'm not very good at this stuff yet.

SPECIFICATIONS:
SOURCE MATERIAL:InGaN
EMITTING COLOUR:White
LENS TYPE:WATER CLEAR
LUMINOUS INTENSITY-MCD:4000 TYPICAL/5000MAX
REVERSE VOLTAGE:5.0 V
DC FORWARD VOLTAGE:3.3V TYPICAL
DC FORWARD CURRENT:20mA
VIEWING ANGLE:+/- 15 degrees
LEAD SOLDERING TEMP:260oC for 5 seconds

nos_slived · Post by **nos_slived** » Tue May 03, 2005 6:25 pm

I just fixed a mistake that I made.

Yes, your LEDs are 20mA.
I don't know what voltage your screen uses, but for the PS1 screen, you go from the 7.2V in, and you have:

Code: Select all

R=(Vs-Vf)/I
R=(7.2V-3.3V)/0.02A
R=3.9V/0.02A=195ohm

Remember that I depends on how many LEDs you use. If you use 3, then it would be 0.06mA (0.02*3).
I can't remember what system you are using, but if it has a 7808, you already have 7.2V.

For an easy calculator, use this.

goodie · Post by **goodie** » Tue May 03, 2005 7:26 pm

According to that calculator, it looks like I need a 47 ohm resistor. Thanks.

goodie · Post by **goodie** » Wed May 04, 2005 12:10 pm

Yay! I did the LED mod with 2 of those LEDs and a 47 ohm resistor, and after some adjustment it looks quite nice!

The only problem is that to shove the LEDs in far enough, I had to remove all the diffusing plastic and stuff. In the process I must have accidentally got some dust/oil on the plastic. So there are a few darker spots on the screen. But I guess I can live with it.

Or maybe I'll take the whole thing apart again and use some alchohol on it...

Anyway, now I can finally finish my NESp. I can't wait.