# Halloween Village Led Project

#### ams0401

Joined Sep 12, 2013
35
Hello everyone, I decided to start a project for my miniature Halloween village. The idea is to wire in led's within certain parts of the decor. I have very little experience with wiring or working with pcb boards. I have looked everywhere and can't seam to find what I'm looking for, I know what I would like to do in my head but I need help with getting it on paper so I can get some boards built.

Basically I want to build a board that has a 12v supply, the led's will be grouped in three's run in series, with about 10 groups on each board. I drew a rough idea of what I want, I need help with the design and if I even did it right anything will help thank you.

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#### wayneh

Joined Sep 9, 2010
17,154
You're on the right track, and I'm not sure what you are asking. There are two main electrical concerns; each string needs the proper resistor to limit current, and the total current of all the strings in parallel needs to be less than the rating of the power supply, say 80% or less.

Beyond that, it's just choosing colors and arrangements and such. You might have to worry about power (heat) dissipation if these are high power LEDs, but if they are "normal" the heat is not a problem.

Do you really want the LEDs on a board, and not placed strategically around your other decorations?

#### #12

Joined Nov 30, 2010
18,223
Good start. Now pick some LEDS and find out what voltage each one needs, then calculate a resistor. Your garden variety LEDs have a 20 ma current limit. If each one needed 3 volts, you would use the remaining 3 volts to figure a resistor like this:
R = E/I
R = 3/.02
R = 150 ohms minimum

I prefer not to drive LEDs at their absolute maximum survivable current, so I would use at least enough resistance to take the current down to 18ma or less.

#### ams0401

Joined Sep 12, 2013
35
Thank you for your response I will be using a 12v dc for the power sorce. Each set of 3 led's will have their own resistor Ie (120ohm for 3 green led's, 300ohm for 3 red, etc). The led's I am using are (Emitting color: Red, Diameter: 5mm, Forward voltage(V): 2.0-2.2, Current(mA): 20, Luminous intensity(MCD): 8,000 - 12,000). As for the last part I don't want the led's on a board i do want to place them around my decorations, I only put it on the board cause when I tried to save it as a pic it didn't show up on the white background. I guess what I'm trying to get at is I would like some help on designing a pcb board to hold the 12v barrel jack, the individual resistors for each set of led's, and a place where I can solder wires to the board or through a pin connector or something like that I will draw the picture like maybe that will help more.

#### ams0401

Joined Sep 12, 2013
35
Here's a rough drawing of what I want to do hope its not to bad.

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#### #12

Joined Nov 30, 2010
18,223
I use point one perfboard, pad-per-hole. You can get it at Radio Shack. It's a grid of holes 1/10th inch on center. Each hole has a doughnut of copper around it. Stick a wire through the board and solder it to a pad. Then strip some wire and use it to jump from pad to pad to make circuits. Dirty looking, but fast and cheap.

#### ams0401

Joined Sep 12, 2013
35
Ok here is my final mock up, of wiring the route's and what not please tell me if its correct or if I need to make changes. Thank you

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#### #12

Joined Nov 30, 2010
18,223
Looks good from here, but I wouldn't bother making 5 separate lines for 5 points that go to the same place.

#### ams0401

Joined Sep 12, 2013
35
Do you mean just run all the - into one wire and one pin?

#### Tatman

Joined Sep 13, 2013
5
Yep mate you only need to run one common cathode all the way from the leds back to the pcb thus cutting down on the amount of wire u will have running around your village