Double Resistor for Red P4

[Darth Enab]

I just got my saber parts in today, (yay! :D) but I was told with my 1 ohm 2 watt resistor I might blow up my P4. Source voltage is 3.6 volts. I was wondering if I could double resistor and use a 0.47 ohm 5 watt resistor. Could it work?

[Azmaria Dei]

in theory yes, but i would urge you to just use a single resistor to prevent the possibility of complications.

[Rhyen Skytracker]

You need to have both resistors at least 2.5 Watts and you need a 1.1 or greater resistor.

[strengthofrage]

Would this fall under the "path of least resistance" rule?

I think you would have an easier time just using the proper resistor instead of doubling up.

[PhoenixReborn]

Just use a 1000mA buckpuck. It slightly overdrives the P4, but the P4 can handle it.

[Azmaria Dei]

Just use a 1000mA buckpuck. It slightly overdrives the P4, but the P4 can handle it.

i've heard some people say their red P4 takes that well and i've heard others report letting the purple smoke out. also, the resistor option is MUCH cheaper, and i think that might be one of the deciding factors here...

[Rhyen Skytracker]

The Red P4s are very sensitive and you can't overdrive them much at all. I have had some work directly off of a MR FX board and only use 5 of the - wires and it worked fins and I have had others the fried with the same set up in less than 2 seconds. It is up to what risk you are willing to take. A buck puck should be fine since it is a true LED driver and regulates the current, but with other set ups be very careful.

[polarcupz]

The Red P4s are very sensitive and you can't overdrive them much at all. I have had some work directly off of a MR FX board and only use 5 of the - wires and it worked fins and I have had others the fried with the same set up in less than 2 seconds. It is up to what risk you are willing to take. A buck puck should be fine since it is a true LED driver and regulates the current, but with other set ups be very careful.


Would you suggest a 700 ma buckpuck on top of a fx board with a 3.7v Li ion and a red p4?

[cardcollector]

Just sO you know, you can feed p4s up to 1000ma without damaging them. But if you give them just a little bit over the rated voltage... Bye-bye led...

[Azmaria Dei]

polarcupz - i would suggest an MR board with a 1 ohm 2 watt resistor and a red P4. the MR board will put out (normally) 1000-1200mA at 3.5V so resistoring it based on that brings it down to just what the LED wants (and can run at safely)

[PhoenixReborn]

If you're seriously worried, go with the Rebel Red (its a little dimmer), or a Lux3 Red (Higher current)

[BeamiestRocket4]

If you use an MR board with a 1000Ma buckpuck would that diminish the brughtness or would it be fine. I am doing a rebuild on my first saber gonna get an MR soundboard and recharge port. If i feed the board 4.8V from the NiMH Batts would it be better to use a buckpuck or a resistor. This is the first time using an MR board and thought you didn't have to use a resistor but i know that the new P4's are touchy.

[Azmaria Dei]

the board and the puck are both LED drivers - running both in series is overkill, takes up a lot of room, and is expensive. for a P4 red, just put a 1 ohm 2 watt resistor on the LED output from the MR board and that'll cut it down to what it can take. the other P4 LEDs are fine running directly off of the driver in the soundcard.

i also don't think the puck would like being limited like that since the sound card LED driver circuitry normally puts out 3.5V @ 1000mA... it has to have SOMETHING to operate off of and if everything is needed for the LED...

[Darth Enab]

Does the voltage of the resistor really matter since voltage equals current times resistance? Also, what would be an approximate runtime for my saber?

[Azmaria Dei]

resistors don't entirely care about voltage... and i'm not so sure about your formula... and to calculate runtime i'll need some more specs - battery type and rating, resistor used, soundboard, anything else like accent LEDs...

as for the LED, normally i would say no, voltage doesn't entirely matter unless you go crazy with it and direct drive it with something insane. as for the red P4 though... they tend to be fickle... resistoring them properly will allow them to take the voltage and power levels they need, so there's no worries on that. ^_^

[dgdve]

you can never (real world)calculate the run time(and why bother) to an exact point because of things like power creep and idle/sleep losses..plus your battery will perform differently at different temperatures NOT just charge levels.. little things like bad solder job, old or aging battery, too much extra wires or connections... basically everything can effect your run times.. suffice it to say as long as your using one of the battery solutions thats been commonly used here your run time will not be an issue at all