Stunt saber power question

[Duhjoker]

    Hi guys

     What is the lil cylinder piece that's soldered to the ground wire on a stunt saber with standard set up?

     Also do you carry an AV switch or LED lit switch that will work with the above?

[Racona Nova]

The piece (if you didn't choose otherwise) should be the resistor preventing the LED from burning out.
And US has added latching AV switches for stunt sabers to their parts' line-up recently. Just ask them ([email protected]) for upgrade prices etc. if you want to change your switch to an AV switch I don't know if illuminated AV switches for stunt sabers are also available, but asking them should definitely help!

[Duhjoker]

 Don't suppose you would know the correct resistor to use would you?

[Racona Nova]

No, unfortunately not. I'm not doing much electronic work (actually I never built a saber yet), but someone from the DIY section should know.

[MdWolfen]

The latching switches are smaller in diameter than the AV switches. If you have a latching switch, then chances are the hole will be a tad smaller than what the AV switch would need. As for the resistor, you can use this calculator......
http://led.linear1.org/1led.wiz

You need to know your source voltage, led forward voltage & current though.

[Duhjoker]

  Ive tried using the calculator and never can find what its telling me i need. It would be easier if some one, maybe a staff member, could tell me the exact part. Im just replacing the one it already had.

[MdWolfen]

 Ive tried using the calculator and never can find what its telling me i need. It would be easier if some one, maybe a staff member, could tell me the exact part. Im just replacing the one it already had.

Do you still have the original resistor? Look at the color bands running around it. Google 'Resistor Color Codes' and try to find what you need. Here is one you can try first...
http://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-resistor-color-code-4-band
US is VERY helpful and their Customer Service is awesome, however, I have been told in an email from US that 'We do not provide assistance or technical support.' Hope you find the one you need.

[Duhjoker]

 Yes i emailed CS and still waiting. I know they are busy so it might take a day.


    I do have the Resistor. It had a white or gray covering with the markings

   2•0 ohm (symbol) 5%

    5N2 ?

   3w

[Duhjoker]

[MdWolfen]

I sent those photos to my brother who is an electronics technician. Obviously a multi-meter would help, but, from just looking at it, he believes it's a 2 ohm 3 watt resistor. The 5% means that it's accurate within +/- 5%. If it's a single Green led, then this resistor sounds about right.

[Duhjoker]

  Awesome!!! Thank you so much!!!!!

[MdWolfen]

 Awesome!!! Thank you so much!!!!!

No problem buddy. I just hope that helps and that it's the right one.  

[Duhjoker]

    Ok so today I decided to wire my existing resistor back to the negative wire. I think I have it right since the short side was going to the battery.

    I've got my multimeter out and I can see that the juice is reading but when I put it on ohms and check the positive and negative wires but it just say 0.

   How do I test it properly?

[Vyk]

Well, first, it's worth noting that resistors don't have polarity, so it doesn't matter which way around you put it in.

When you say "check the positive and negative wires," where exactly do you mean?

It's important to realize that LEDs (and semiconductors in general) don't behave intuitively.  A light bulb has a fixed resistance; if you put an ohmmeter on it, you'll get a reading off of it.  An LED does not work the same way; if you put an ohmmeter on one, you'll generally get no reading--an open circuit.  The reason for this is that an LED has a minimum voltage below which no current flows, and ohmmeters don't put out that much voltage.  The resistance also varies with voltage, temperature, and possibly some things I'm forgetting; if you look up the spec sheet for that model of LED, you can find graphs that will show you those variations.  (Incidentally, that's why the LED is in that metal heat sink--if you don't dissipate the heat, the resistance lowers, so the current goes up, so the temperature goes up, so the resistance lowers, and so on until the LED fries itself.  This is called thermal runaway.)

The wiring in a stunt saber should go roughly as follows: from the battery pack, to the switch, to the LED, to the resistor, back to the battery pack.  Of the components, only the LED and the battery pack have polarity; also, it doesn't really matter what order the components are in.

If I had a saber that wasn't working, I'd take out the batteries, cut away the heat-shrink tubing, and test the following:
Ohmmeter on both sides of the resistor; should read between 1.9 and 2.1 ohms (2 ohms +/- 5%).
Ohmmeter on both sides of the switch; in one position, resistance should be infinite; in the other, it should be really close to zero.
If those are ok, point the LED in a safe direction (ie, not pointing at anyone) and put the batteries back in.  If you're really lucky, the electronics fairies are smiling on you and it's working now.  If it isn't, switch your multimeter to DC voltage and start testing.  Test right near the battery pack; should be about 6V with alkalines, about 4.8V with NiMH.  Then just work your way up the wiring.  If at any point you no longer have voltage, you've found your problem.  (Assuming you didn't accidentally turn the switch back off!)  If you're at the LED and there's still voltage on both sides, but the LED isn't lit, you either have a broken lead in the LED, or you have a burnt-out LED.  (Hope for the first one.)

If you found a problem before getting to the LED, you're 90% there--just fix the problem.  If the switch and resistor both worked, then it's a problem in the wiring; take the batteries back out and start probing with the ohmmeter.  A length of wire should be very nearly zero ohms; if it has significant resistance or if it's an open circuit, there's a break in the wire.  Also check the solder joints where components meet wires; the easiest way is to put one probe on the opposite side of the component, and the other probe at the opposite end of the wire.

If you were fine other than the LED, it's time to take a closer look.  Unscrew the bottom of the LED module.  Inspect the wiring connecting to the LED star.  If a connection is broken, you found the problem.  If everything still looks good, that's bad.  Maybe somebody else here has a further suggestion, but to the extent of my knowledge, you have a dead LED.  Hopefully, though, you will have found the problem long before here.

Let us know what you find.  Good luck!

[Duhjoker]

    The resistor was working but when the lil solder nubs broke off with the wire i thought it couldnt be re-soldered back but i did any way and it seems to work. When i check the leads past the resistor i still get about 5.32v. But i have no idea if its resisting.

   Ok i figured out how to test it and used my multimeter and i am getting between 1.7-2.0.

So it doesnt matter which way the resistor goes on the wire? Whats the signifigance of the resistor being on the negative lead?