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Old 03-14-2013, 09:18 AM   #15
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Two Options

Trying to insulate the LEDs will cut them off from their only method of heat dissipation and lead to an even earlier demise or the LEDs. I wouldn't recommend it.

There are two ways of accomplishing what needs to be done. The least expensive is with the voltage regulators. (Sometimes referred to as 'Buck' converters). They come iin all shapes & sizes. I chose ones that would mount in the space at the end of the fixture opposite from the switch. They are about 1" x 3/4" in size.

Another way is to use a pulse width modulation (PWM) dimmer. These basically turn the LED's on & off thousands of times a second. The percentage of time the LEDs are on is perceived by our eyes as brightness.

My feeling is that even with a PWM dimmer you still need a voltage regulator in the circuit before the dimmer. Unless the dimmer has one built in?

When I worked in the semiconductor industry we said that too high a voltage would turn a LED into a NED (noise emiting diode) and then into a DED (darkness emitting diode). (and only a software guy like me would think that's still funny )
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Old 03-14-2013, 09:27 AM   #16
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Thanks Muddypaws for your expertise. I am looking at the voltage regulators now on Ebay. The small one that I see it appears that they are rated for output current 2A max or 3A with additional heat sink, and rated for 15 watts without additional heat sink. I think my 6 strip light is putting out 35 watts and 2.88A. Did you use additional heat sinks?
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Old 03-14-2013, 10:42 AM   #17
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2.88A? Yikes!

I have 4 strips of 5050 LEDS in each fixture and the current draw at 10.5v is just barely over 1A. I ran the whole roll (15 feet) of LEDs with a 12v regulated 1.5A supply for several hours.

I used the 3A ones, no additional heatsink was required as they only got up to about 20F over ambient. The big capacitor near the output pads was the only part that even felt warm to the touch. I used a cheap-o IR thermometer to measure temps.

I found the 2A ones for < 2 bucks and the 3A for just over $5 this morning.

In mounting the boards inside the fixture I used 2 nylon stand-offs to keep the solder side of the boards away from anything conductive. If you want I can attach a picture later today.
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Old 03-14-2013, 11:23 AM   #18
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This is not the specs from the ones I ordered (mine didn't give all this information) but they are for the same SMD 5050 light strips. I am reading this to say the current is 1.0-1.2A per meter. My 6 rows added up to about 2.4 meters X 1.2A = 2.88 Amps. Am I figuring this wrong? Thanks for you help.



● Color: cool white
● View angle:120
● Working Voltage: 12VDC
● LED Quantity: 300 leds/5 Mete
● Working Current/meter: 1.0-1.2A
● Output power: 60-72W /5 Meter
● Working Tempreture:-20 to 50
● Protection Rate IP65(waterproof)
● Luminous Flux: 750-900 Lumens/Meter
● Color Temperature: 6500 --7500K
● Size: L500cm (5M) x W1.0cm x T0.25cm

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Old 03-14-2013, 11:51 AM   #19
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Voltage VS Current

I'm running them at reduced voltage. Less voltage = less current = less heat = longer life. I measured it with the only DMM I have. It's a Craftsman and is probably not accurate out to 6 decimal places but it's not a total piece of junque either.
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Old 03-14-2013, 12:55 PM   #20
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[QUOTE=Muddypaws;
SNIP.

I used the 3A ones, no additional heatsink was required as they only got up to about 20F over ambient. The big capacitor near the output pads was the only part that even felt warm to the touch. I used a cheap-o IR thermometer to measure temps.

I found the 2A ones for < 2 bucks and the 3A for just over $5 this morning.

ISNIP
[/QUOTE]

How about a link to what you recommend for a voltage requlator?
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Old 03-14-2013, 01:36 PM   #21
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Thanks, guys! There's a lot of great information here!

I'm not sure if I want to go the route of adding in the voltage regulator(s) or not. At <$20 for 16 feet of LED's, even if they only last a couple of years, they're still cheaper than fluorescent bulbs!

But I'm curious... is there a voltage regulator with enough power output to put one close to the batteries and just regulate the whole coach? I would think that everything would benefit from being shielded from the voltage irregularities of the charge/discharge cycle.
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Old 03-14-2013, 05:28 PM   #22
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Quote:
Originally Posted by Muddypaws View Post
Trying to insulate the LEDs will cut them off from their only method of heat dissipation and lead to an even earlier demise or the LEDs. I wouldn't recommend it.

There are two ways of accomplishing what needs to be done. The least expensive is with the voltage regulators. (Sometimes referred to as 'Buck' converters). They come iin all shapes & sizes. I chose ones that would mount in the space at the end of the fixture opposite from the switch. They are about 1" x 3/4" in size.

Another way is to use a pulse width modulation (PWM) dimmer. These basically turn the LED's on & off thousands of times a second. The percentage of time the LEDs are on is perceived by our eyes as brightness.

My feeling is that even with a PWM dimmer you still need a voltage regulator in the circuit before the dimmer. Unless the dimmer has one built in?

When I worked in the semiconductor industry we said that too high a voltage would turn a LED into a NED (noise emiting diode) and then into a DED (darkness emitting diode). (and only a software guy like me would think that's still funny )

Now that's funny! - LOL!!!
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Old 03-14-2013, 05:29 PM   #23
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The metal housing should act as a heat sink if you can couple it to the heat producing parts....
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Old 03-14-2013, 06:14 PM   #24
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No luck

I looked for the 3A regulators and could not find them. Apparently nobody makes the exact one I used anymore.

I found some that output 2.5A without a heat sink and those would be OK if you're going to turn the voltage down.

This link will take you to a 5 pack of them : 5pcs LM2577 LM2577S DC to DC Adjustable Step Up Power Converter Module Arduino | eBay

I used the waterproof LEDs. If I did more fixtures I'd use the regular ones. They are a total PITA to solder.

Don't waste your money on the connectors! They fail 80% of the time and you'll end up soldering anyway.
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Old 03-15-2013, 09:23 AM   #25
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One of the main differences between the cheap strips and the expensive bulb-like led tubes is the voltage regulation. They will work properly and run at a steady level of brightness and temperature regardless of the source voltage. For an RV, which can realistically have system voltages anywhere from 11.0 to 14.4 dcv, that's an advantage.

The Revolution and Ming brands are also polarity-independent, so you can't screw up and get the positive and negative wires reversed. For inexperienced people, that extra measure of insurance is a wise precaution!
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Old 03-16-2013, 04:03 AM   #26
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i did some voltage an amp test last evening. I used 5 strips of the 5m 3528, 300 SMD Cool White and they must have built in regulators, as I don't notice any change in brigthness. They might not last as long, but I still have ~4m left. They are not hot to the touch and both my onboard 4 digit and 117 Fluke True RMS (highly recommened by Motor Motor magazine) pretty much agree. if the pic isn't clear, the onboard one show 14.16 volts while my 117 shows 14.28. I took many pics and this is the best I could post.

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Old 03-16-2013, 11:26 AM   #27
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I used this boost-buck regulator with my fluorescent LED upgrades: Auto DC-DC Boost Buck Converter Solar Voltage Regulator 25W 3-30V to 0.5-30V

Here's a thread of mine with details over on the Winnebago forum: LED Upgrades

For a 12" 2-bulb fixture I used 4 12" 5050 SMD LED strips (18 LEDs per strip) and one regulator for a total cost of just over $11.

For the 36" 2-bulb fixtures I will be using 4 36" LED strips with two regulators (due to the 2A rating of the regulators).
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Old 03-16-2013, 12:01 PM   #28
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Heat!

My focus on using voltage regulators was to control the heat soak into the fixture. Each of my fixtures has 4 18" strips.

After about 30 minutes the entire aluminum extrusion would be warm enough to be uncomfortable to touch. I figured that much heat could and would damage the vinyl components in my ceiling. I forget exactly what the temprature was but think it was around 180F and still climbing.

Others have reported that the strips have come unglued. I suspect they might have gotten hot enough to melt the glue.

If the individual LEDs are hot to the touch they are drawing way too much current. I can run mine for several hours and the fixture will barely be warm to the touch. It's much cooler than the original flourescent. Coolness is good IMHO.

I'm pretty sure a 2A or 2.5A VR would be adequate with the voltage trimmed down to exactly 12v, even better at <11v.
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