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Discussion Starter #1
I have 10 of these, each with a resistor with a 3v max. So, can I wire these in series together and run the power from an old Tyco power pack and not exceed 2-3 volts on the throttle?
 

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Yes you can. Be sure to lock the Tyco speed control so
it can't be changed from the 3v setting. If, as I assume,
the streetlights are LED you won't be overloading the Tyco.
You will need to observe correct polarity as you connect
the lights together.

Don
 

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Discussion Starter #3
Correct polarity means the resistor to the same wire on each light, usually the longer one, right?
Thanks
 

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Yes, the long wire on an LED is Positive. It would be good
practice to have the resistor on the same leg on each LED.

Don
 

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Why mess with a long series connection? You save a little wire, but that's it. If they have a resistor connected to them that allows them to operate at 3 volts, that means 10 in series might require 30 volts. I think you meant to wire them in parallel and use the old tyco power pack set to 3 volts. You really should test that old power pack to make sure its easy to lock the throttle at 3 volts. You might consider connecting 2 lites in series then connect these pairs in parallel, then you could adjust the power pack somewhere between 0-6 volts to get a little control over the brightness. If you really want to full dim to bright control, you need to think about a pulse width controller as LED's will not act like incandescent lites in terms of dimability.
 

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Note that connecting LED's in parallel then using a single resistor will not work as once one of the LED's triggers none of the others will.
 

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I would not recommend doing this. Remember that there is a 1-2V drop across each LED. This means if your power supply puts out 3V and you have 12 LEDs in series there will be approximately 0 volts going into LED #4. This means that none of the LEDs will light because there is not enough voltage to turn on all the LEDs. You would need at least a 24 volt power supply to operate the circuit of 12 LEDs. Also, you're going to end up creating a 1950s string of Christmas lights. If one of the LEDs would fail the whole string would go out.
 

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I would also advise against trying to rely on any old variable power supply to provide a specific voltage. For that matter, I'd be surprised if you can get that Tyco power pack to even put out a reliable 3 volts. These old things work on a variable resistor, which means even if you superglue the throttle in place, that voltage is going to drift from changes in temperature, humidity, or how many people are currently looking at it. In other words, there is no way to accurately lock it down to a specific voltage. And keep in mind that LEDs are very sensitive to voltage, so if you drift more than 1/4 to 1/2 of a volt, you're going to blow the LED.

The way I look at it, you could spend a couple bucks now for a small power pack that provides the correct fixed voltage, or you could replace your entire string of lamp posts every few months.
 

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Got an old computer lying around with a power supply that still works?
 

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Discussion Starter #10
I would also advise against trying to rely on any old variable power supply to provide a specific voltage. For that matter, I'd be surprised if you can get that Tyco power pack to even put out a reliable 3 volts. These old things work on a variable resistor, which means even if you superglue the throttle in place, that voltage is going to drift from changes in temperature, humidity, or how many people are currently looking at it. In other words, there is no way to accurately lock it down to a specific voltage. And keep in mind that LEDs are very sensitive to voltage, so if you drift more than 1/4 to 1/2 of a volt, you're going to blow the LED.

The way I look at it, you could spend a couple bucks now for a small power pack that provides the correct fixed voltage, or you could replace your entire string of lamp posts every few months.
So what exactly would be the best power pack? Eventually, I will have 20 LED lights at 3v each so I need the right power.
Thanks
 

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That thing is way overkill for LEDs. I use wall warts. Belker makes I've that you can set the voltage on from 3-12v in 3a it I think 6a variety. That's plenty to run a ton of little LEDs. Usually they are somewhere around 20ma each. Get a wall wart and a distribution board.

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Discussion Starter #14
Each lamp needs a resistor, right? and I'll wire it in parallel to a power source but else besides the Menzo?
Do wall warts just connect to the wires and plug it in? No control?
 

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Depends on how you do it. I use a wall wart to power a small distribution board. The LEDs connect to the board. I wired a switch to the wall wart so I leave it plugged in and just flip a switch to turn on all the lights.

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I used something like this and give each lamp it's own resistor. I also run 12v, that gives me the ability to run multiple types of lights off the same board, just vary the resistance. I have three distribution boards chained together so there is one close from anywhere on my small layout.

Fwiw,I have no idea how others do it. This is just how I run mine. I'm sure there are more elegant solutions.

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Can you clarify something here? First. you keep asking about resistors -- do your lamps HAVE resistors built into them already, or are you planning to add your own? Second, where did the 3v value come from? Is that what the manufacturer specifies (and I assume is correct for resistors that are already built in), or did you see that some LED's run on 3v and assumed that you just need to plug them all in to a regular 3v source?

The answers to both of these questions actually make a huge difference for what you're planning to do, so don't buy anything else until we have these items answered. There are likely better ways to do what you want!
 
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