Double Checking my Hypothesis...

[Inferno]

Man it's been a while sense I've last posted something.

Anywho, I have a friend who purchased a stunt saber from another site and felt the need to add sound to it. The saber came with a 4 aaa holder for it's power source and used a resistor to protect the Red Seoul P4. I can't say what ohm/watt resistor was used in it's original build. My friend chose to gut his converted MR05 Vader for the sound board and speaker. He changed the power solution from the 4.5v/3 aa battery pack to the 6v/4 cell aaa pack. He also direct wired the LED to the board. Well the LED is dead and no broken solder joints were found. At this point he handed the repair job to me. Despite his horrid attempt at building a chassis to hold the board (Part of the Vader's and Electrical Tape), the board seems to function fine. From what I understand the board can take the 6v max. But when I checked the voltage at the LED, I found it reading almost 6v. So I'm thinking that in order to repair this saber, I'm gonna have to place a resistor in line with a new red P4. I ran a resistor calculator and it called for a 2.5 watt or better 3.9ohm resistor based on the P4's fV and mA specs for the Red. I would like to use the 20mA DynaOhm resistor, but it's out of stock. So I'm thinking of using the 3.9ohm/5w that is available. If I am wrong in this line of thought, please let me know.

[Kyaryo Ysoyav]

I can't comment on the specifics of the resistor (I don't have time right now to check the calculations), but a 20mA resistor would definitely not work with a main LED. Those are for the LEDs in AV switches, and would only provide 20mA of current to something that would need 500-700mA or so.

[FenderBender]

Yeah, he blew the LED. Putting 6v worth of power to the board using AAA's was pointless as well. He was better off with the 4.5VAA pack as you get more current and the voltage drop isn't as large so you don't need as big a resistor. With the 6V, you're going to need a 5W resistor (the big white ceramic jobs) to soak up all that heat. I would suggest using a single 18650 with holder. This way you only have to use a 2W 1Ohm carbon film resistor (small) and you get WAAAAAYYY more run time and an overall brighter blade.

[Inferno]

Thanks for the info FenderBender. I'm probably gonna order multiple of these resistors today.