2010 hasbro obi voltage issue

**Danz409** · 10-10-2010, 02:44 PM

ok. i talked to a few in the shout box about this issue and nobody can seem to find whats wrong. my problem is. no matter what voltage input. i never can get more then 2.2v at the LED.

here are the layouts and pics

in this pic the resistor is glued on the back of the board and the transistor connects to it trough the hole in the middle of the board

oddly voltage tested on the LED + is just fine. same as battery +. but when i go testing any other voltage using the -
ground from the LED- i get voltages WAY short of what they should be. only get .6v testing the main + from battery against it

anybody know what the issue could be? only thing i can think of is a bad board and forced to find another means
of lighting up my LED effecntly. first i thought heck. maybe more input voltage = higher output voltage. so i
swamped out the 4x 1.2v rechargeables for 5x alk batteries 4x in the 4 holder and added a single cell holder for
a total of 7.5v input. and STILL only get 2.2v at the LED even without a resistor!

**jin starkiller** · 10-10-2010, 03:17 PM

from your diagram looks like it is wired wrong

this is way mine are wired try this

**Ari-Jaq Xulden** · 10-10-2010, 03:17 PM

I have never seen it hooked like that. Its probably cause you have the resistor in line with the input voltage and the the transistor itself. Try putting between the transistor and led for the specif led. No resistor and find your missing voltage you should.

**Danz409** · 10-10-2010, 07:11 PM

Originally Posted by jin starkiller

from your diagram looks like it is wired wrong

this is way mine are wired try this

srry for the slow reply. been doing some yard work all day fallowed by shopping. didn't get to play with sabers today. played with this and HOLY CRAP! im getting 3v at the LED! probably too much for red in the long run. is that a safe overdrive voltage for P4 red?

i <3 you jin. me and a few other spent forever trying to figure this out!

**jin starkiller** · 10-10-2010, 07:13 PM

no prblm did my fair amount of research for wiring up these boards

also help from card collecter and a few others here on the forum

**Danz409** · 10-10-2010, 07:35 PM

by the way. this is what i used to make mine.

found here in the froums

http://forums.thecustomsabershop.com...+hasbro&page=2

so if anyone comes across this issue. here be the answer!

oh and 5v isn't in the resistance calculator. and i can't seem to figure out the formula for figuring it out. i know its ohms law.
but what mix of what and what to do what. for example my LED is a: P4 red. 800 ma. @ 2.5v forward voltage. and source would be 5v. iv been beating my self up not being able to figure this out lol

**Danz409** · 10-10-2010, 09:09 PM

ok. i discovers how to find what resistor your need for ANY given LED. it is indeed ohms law. i just couldn't figure how to apply it. until today!

Ohms law is

and to figure it out. you take your current battery voltage. say im useing a 7.2 (2x 18650s) and my LED specs are.

3.85V @ 1500 ma (blue K2)

what i first need to do is subtract the volts i need from the total to get difference i need to change it by. which is 3.35v

that is where i was stuck. now i can apply ohms law

i need to divide the 3.35 by the 1.5 amps to get resistance which comes to
2.23 ohms!

and to find the wattage of the resister requirements.
you take the voltage difference 3.35v and multiply by the amps 1.5 and get
5.025 watts!

glad i finally (re)discovered this. i remember this being one of the first things thought in my class... can't believe i forgot it lol.

**RevengeoftheSeth** · 10-10-2010, 10:46 PM

Yeah, it looked to me like your resistor was in the wrong spot. I didn't really look much past that once I saw it, though.

Your calculations for the resistor are probably off if you are using a voltage regulator.

(For P4 Blue)

5Vs-3.85Vf = 1.15V

1.15V/1.5A = 0.77 Ohms

1.15V*1.5A = 1.73 W

TCSS sells a 1Ohm 2W resistor in the store. Use that and you should be good.

(For P4 Red)

5Vs-2.5Vf = 2.5V

2.5V/.8A = 3.13 Ohms

2.5V*.8A = 2 W

Use the 3.3Ohm 5W resistor if you are buying from TCSS (that's the closest one)