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# Electronic Components/LED lights

Question
I am wanting to make a led light panel.  I have 100 1 watt LEDs and a LED driver.  The driver has this written on the top of it.     led driver
input: ac 100-265v 50/60Hz
output: dc28-38V 3A +_ 3%
led power: 100W
PF:>0.95

My plan was to plug the driver into the wall and wire it into the lights in series.  Before I do all of the soldering will this set up work? If not any suggestions on how to make it work.

Thank You

The wiring of your panel will depend on the characteristics of the LEDs that you are going to use. Typically, a 1-watt LED will have a Vf (forward voltage drop) of about 3 volts. With the output of your driver being 28-38 volts, this means that it will power about 10-12 LEDs in series. So what you would probably need is a series-parallel circuit with 10 groups of 10 LEDs all wired in series.
Also, you will want to make sure that the current is maintained properly in each leg of the circuit. An average forward current for one of these devices is 300 - 350 mA.
So, doing some simple math, we have 10 LEDs in series, with an average forward voltage drop of 3 Volts each. The total voltage drop is 30 volts, leaving 8 volts to make up. We want to set the current at 350 mA. So, using Ohm's law, (R = E/I), we know that our resistor has to be 8/0.350, or about 21 Ohms. That resistor will need to handle just over 2.5 watts, so I'd use a 3-5 watt resistor.
There might be a temptation to just use 11 or 12 LEDs in series, and no dropping resistor, but if you do that, you run the risk of having one chain of LEDs dropping all of the current. So the resistors help insure that no single group of LEDs is handling most of the current.

Of course the numbers above are based on assumptions of various generic components. I can't be certain about your particular LEDs - you will need to look up the specifications for their particular forward voltage drop and current requirements to make a more accurate assessment. You can use the procedure above to calculate the requirements for whatever variety of LED you have.
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Electronic Components

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#### Deirdre Hebert

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I can answer most questions regarding electronic components, what they are and how to use them.

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I worked for a number of years in the electronic component testing industry, designing and building automated test equipment for the electronic manufacturing industry.

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