SOoooooooooo...a few years back I bought a few strings of xmas tree lights...LEDs. They are small dome shaped and work great for lighting bulidings etc. Now....I dont want the distance between bulidings to be constrained by the length between lights on the string. So my questions: 1) Can I cut them off and use them as individual lights...to spread them out ? 2) whats the usual voltage on these things ? 3) are they AC or DC ? 4) can they be run in paralell or wired in series...or both ? I dont see anything at the plug that indicates a voltage drop or current change. Although the wire to each bulb is pretty small diameter...hmmm. I just cant see these thing being 110V !! If the fact that with them all wired together in and of themselves...drops the voltage to each bulb....how do i get around that...to use em as individual bulbs ? Say 3 bulbs versus 25 ? TIA .
Absolutely! 3V @ 20mA DC (you can run them on AC, however they will flicker. This is because AC alternates + to -, so every time the voltage is in the reversed part of the cycle they will not light. That being said, US AC cycles at 60Hz. So you may or may not notice the flickering. Using them as they are in the Christmas light string you may be able to see this since they are running on AC.) Doesn't matter. Just adjust your resistor size accordingly. Here is a link to calculate what resistor you need for single parallel and series. It doesn't hurt to up the resistor value a little. If you do it too much the LED will dim or not light at all. NEVER under-size the resistor, you will fry the LED. One 3V 20mA LED running off of a 12V DC power source will need a 470ohm resistor. In this case I would use a 680ohm, sometimes a 1000ohm resistor. When you start pulling the LEDs out of the string you may find a couple resistors soldered to the leads. Just remove and discard them, those are calculated for many LEDs on 120V AC. If the LED doesn't light and you have the correct power supply and the correct resistor, turn the LED around. They only light one way. Here is a link to a diagram of a LED. Since the leads are probably shortened already to fit in the string you can tell which is positive by looking inside the epoxy lens. :tb-cool:
LED current Stay around 15ma for LED's. From years of electronic experience, I never run anything at 100 percent which would be 20ma. LED Resistor Values Measured with 12.2 VDC supply using 20 ma max current LED's. Values will vary some depending on actual DC supply value. Resistor Current 1000 ohm 9.0ma 750 ohm 12.45ma 680 ohm 13.12ma 510 ohm 16.25ma On line calculator for series/parallel configuration. http://led.linear1.org/led.wiz A digital multimeter that is very good for model railroad work. I bought three of them. Have had them for some years and compare very closely to expensive meters. Some rivet counters will disagree. http://www.harborfreight.com/7-function-digital-multimeter-90899.html Double clip leads. Very handy at the work bench. http://www.harborfreight.com/18-inch-low-voltage-multi-colored-test-leads-66717.html Rich
