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12-07-2009, 01:31 PM   #21
jlandin
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Nov 2009
Mel Bch, FL-US
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Quote:
 Originally Posted by Rick500 Did they all end up the same brightness, wiring them in series?
Yes. However, I ended up changing the light wiring to put the LEDs in parallel. I realized that I mistakenly reused a previous calculation for only 2 LEDs. Now that I'm having 5 LEDs, I don't have enough voltage to put them in series and get the full brightness that I want.

A great site for calculating the resister needed in LED wiring is here. They have calculators for single, series, and parallel configurations. Or you can do the calcs manually with ohms law.

Hopefully another coat of polyurethane after work today.

--
Josh

12-07-2009, 08:13 PM   #22
passedpawn
Waste Allocation Load Lifter - Earth Class

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☼ Clearwater, FL ☼
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Quote:
 Originally Posted by jlandin Yes. However, I ended up changing the light wiring to put the LEDs in parallel. I realized that I mistakenly reused a previous calculation for only 2 LEDs. Now that I'm having 5 LEDs, I don't have enough voltage to put them in series and get the full brightness that I want. A great site for calculating the resister needed in LED wiring is here. They have calculators for single, series, and parallel configurations. Or you can do the calcs manually with ohms law. Hopefully another coat of polyurethane after work today. -- Josh

To spec correctly, first decide what current you want to run through your LEDs (i.e., 20mA is typical). Then, look at the V/I curve in the LED's datasheet to get the Vf (forward voltage) of the LED at that current. Note that this Vf changes with current.

Multiply the Vf times the number of LEDs you have in series. I..e, 2 * 3.3V = 6.6V. Subtract this from your supply (i.e., 12V - 6.6V = 5.4V). Then, the resistor value you need is V/I = 5.4V / 0.02A = 270 ohms.

Resistor wattage is simply V^2 / R, or in this case 0.108 watts. Those common resistors that you can get at Radio Shack are 0.25W, so one of those would be fine.

Wiring them all in series guarantees they all see the same current, and that is the ideal way to do it. They will each have identical illumination. Wiring them in parallel might result in differing illumination due to manufacturing tolerances with Vf.
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12-07-2009, 08:21 PM   #23
Rick500

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KY
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I figured there'd be about a 1.4V voltage drop across each one (since they are diodes), and that the ones further down the chain would be progressively dimmer.

But if it works, it works.

12-07-2009, 10:53 PM   #24
passedpawn
Waste Allocation Load Lifter - Earth Class

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☼ Clearwater, FL ☼
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Quote:
 Originally Posted by Rick500 I figured there'd be about a 1.4V voltage drop across each one (since they are diodes), and that the ones further down the chain would be progressively dimmer. But if it works, it works.
White LEDs (actually they are blue with yellow tint on top) are between 3 and 4V. Red/Green/Yellow are about 2V.

The brightness is controlled by current, so if they are in series they all get the same current, and the same brightness.
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12-07-2009, 11:00 PM   #25

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Stafford, Virginia
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bad ass keezer! You have much homebrew prowess.

12-07-2009, 11:36 PM   #26
Tripod

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Sep 2008
Atlanta, GA
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Very Nice!
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12-08-2009, 12:01 AM   #27
android

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Ames, Iowa
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looking good brother! can't wait to see it finished.
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12-08-2009, 02:37 AM   #28
Rick500

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KY
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Quote:
 Originally Posted by passedpawn The brightness is controlled by current, so if they are in series they all get the same current, and the same brightness.
Cool. I learned something then. It's been a few years since I played around with discrete components...LED technology has passed me by, I guess.

12-08-2009, 02:19 PM   #29
jlandin
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Nov 2009
Mel Bch, FL-US
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Finally done with the polyurethane! Much less messy work ahead. I remounted the newly rewired lights, their switch, and the 12V power cord.

The light switch is mounted on the side of the coffin:

The power wire exits the bottom of the coffin through a hole in the overhang (not through the lid) and down the back between the wood and the freezer:

The power supply makes its way into the compressor compartment where it is plugged into an appliance extension cord along with the freezer cord:

The extension cord now acts as the main power for the keezer:

I left access to the hing screws for removing the entire lid/coffin. This will prove especially useful when I move the keezer into the house!

I started on the gas distribution, but I couldn't get very far as I'm still waiting on some parts. UPS tracking says I can expect the love controller tomorrow and the driptray/gas-fittings/shanks/etc on Thursday.

As for the top surface, after going back and forth on it, I've decided to use porcelain tile for now. I think eventually we'll remove the tile and do the bottle cap mosaic, but for now, it's just too involved.

I've been saving the receipts. I haven't done a tally yet, but when it's all done I'll post a final build cost.

--
Josh

12-08-2009, 04:43 PM   #30
johnnyc

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Jan 2009
North Atlanta, GA
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How did you avoid the refrigerant lines in the side when you drilled for the gas line? Also do you have a plan for the Love temp sensor or just leave it hanging in the freezer?
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