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Old 12-08-2012, 12:04 PM   #1
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Converting spots to LEDs

I've always found the 70s spotlights to be a problem. It's hard to replace the bulbs and modifying them seemed like a job. Problem fixed!

I tried one of the direct replacement LEDs, but the fixture doesn't have any reflective cone, so most of the light is radiated inside the eyebrow cabinet. I guess a wrap of tin foil would have helped some, but doesn't seem like a robust fix.

Using a 10-LED disc really works well. The mounting bracket is a simple "L" shape of 0.025 aluminum, easy to mark and bend in a small vise. The sockets are available for about $0.60 each in packs of 5 or 10 and the LED discs are about $5. (note: there are 6, 9, 12, and 15-LED discs that can be used as alternatives, for more or less light. However, be advised that the way these discs are wired up, the 10-LED version is about 30% more efficient than the 9-LED version. This has to do with having equal series-strings of LEDs on the disc, eg, the 9-LED version has three strings of 3, each string taking about 100 milliamps. The 10-LED version has only two strings of 5, each taking 100 millliamps. You get more light for less current out of the 10-LED version. The advantage of the 9-LED version is that it can operate [dimly] at a slightly lower minimum voltage, something on the order of 6 volts. I know you folks wanted to know this.)

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Disregard the appearance that the LEDs aren't centered in the opening--it's parallax from taking the photo so close.

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The LED discs are tilted a little, so that they point a bit more up and out. I've always thought the spotslights should be installed more around to the aft end of the eyebrow cabinet, which would make them more suitable as reading lights. Tilting the LEDs will help get the light out to where you'd be holding a book, IMHO. BTW, these LED discs have their own rectifiers and regulator, so they can be hooked up +/- and powered with up to 30 volts. If you reduce the voltage down as far a 7 volts, they dim quite nicely.

Zep
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Old 12-08-2012, 12:31 PM   #2
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Interesting. What does the light pattern look like compared to the incandescent bulb? I had bought an LED tail light with the correct base for this very same use, but it was way too dim to be useful. I had thought about using something like a MR16 or MR11 base led mini spot and either soldering in the wire or using some sort of socket. It would be oversize compared to the original bulb but would still be able to fit in the fixture I think. This is what I'm talking about:


These are also 12v lights and dimmable. I've used similar 110v lights in small recessed cans in the house and they have a good light output, fairly directional and very cheap to run compared to the 50w halogens that are common these days for spots.
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Old 12-08-2012, 12:53 PM   #3
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LEDs are directional by nature, which can be an advantage in spotlights but a disadvantage when retrofitting tail lamps.

The earlier discrete LEDs in a plastic dome are most directional. Newer surface mount types have a wider output angle which sometimes approaches 180 degrees.

It is a matter of selecting the right type for the application. The cob type bulb in the spotlight must have been laughably bad, compared to the discs you settled on.

The earlier resistive/series string types vary widely in their efficiency as mentioned; it is a tough compromise (I retrofit some of my own fixtures with discrete LEDs.) More LEDs in a given string means less heat loss in the resistor, but it becomes far more sensitive to the voltage spread between battery voltage and charging voltage.

The latest generation of LED fixtures with a switching power supply and a wide input voltage range (8 to 30, 85 to 265 AC, wow) solve this problem neatly, but give rise to a new one: they are NOISY AS A PARTY with RFI. Try running the radio or TV nearby and turn them on one by one, they each have their own annoying frequency and can set up quite a dissonant symphony in groups. I got some bulk capacitors and chokes on ebay and plan to experiment with filtering at the voltage input.
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Old 12-08-2012, 08:16 PM   #4
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Quote:
Originally Posted by SilvrSausage View Post
...but give rise to a new one: they are NOISY AS A PARTY with RFI. Try running the radio or TV nearby and turn them on one by one, they each have their own annoying frequency and can set up quite a dissonant symphony in groups. I got some bulk capacitors and chokes on ebay and plan to experiment with filtering at the voltage input.
I ran into this problem with an earlier modification and solved it with a 0.1 uf ceramic cap near the socket. I thought I'd need a choke, but didn't.

The socket I used this time is not as amenable to adding the capacitor. I checked out the new lights a few minutes ago and sure enough, one of them is RFI noisy. I'll have to get a cap on it somehow.


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Old 12-08-2012, 08:32 PM   #5
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The socket I used fits G4, MR16, and MR11 lights. You can also get them in packs of 5 and 10.

Here's a shot of the new spots, installed. You can see they have a very wide beam. I think I would like them recessed just a bit more to conceal the LEDs from direct view and to give a bit more of a spotlight effect, but they are OK for now.

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The brightness is about right for reading, but they are a little too bright for background mood lighting. I think if they were more recessed (more of a spotlight) they would be fine for both.

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Old 12-08-2012, 08:36 PM   #6
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I modified the bathroom light with two 15-LED discs. The light cover, as old as it is and yellowed, tones down the light output significantly. I used the 3-position switch to give me a bright and dim setting, switching in a 68 ohm resistor. In dim, the light uses a total of 55 milliamps and puts out more than enough light to use the toilet or wash your hands.

In bright, it uses about 0.5 amps.

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The small clips are intended to keep the discs from vibrating out of their sockets.

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Old 12-08-2012, 08:44 PM   #7
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Originally Posted by Zeppelinium View Post
The socket I used fits G4, MR16, and MR11 lights. You can also get them in packs of 5 and 10.

Here's a shot of the new spots, installed. You can see they have a very wide beam. I think I would like them recessed just a bit more to conceal the LEDs from direct view and to give a bit more of a spotlight effect, but they are OK for now.

Attachment 174205

The brightness is about right for reading, but they are a little too bright for background mood lighting. I think if they were more recessed (more of a spotlight) they would be fine for both.

Zep
Hey Zep, Dan, at LEDs4RVs has a dimmer which works well for those overhead lights. I installed one last year and it works well. Fortunately or unfortunately, depending upon your perspective, it also has several other functions for flashing lights which can turn your AS into a disco! I just use the dimmer, left or right or both on, and on/off functions.

I actually use them for dim nightlights.
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Old 12-09-2012, 09:12 AM   #8
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Hey ZEP. A few years I purchased LED replacement bulbs for our '85 Excella. They had the automotive bayonette mounts. They were very noisy in the radio/ TV. They worked nice and put out good light. I tried to find some solutions but couldn't get them to work. I took them out and kept them but our new ( '01 Excella ) has different mounts so they won't work. I think they are double prong push mounted bulbs. We have 4 of them ( 2 in front and 2 rear ). Are these LED's being used compatable with these mounts or do I need to change the complete fixture ???
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Old 12-09-2012, 04:03 PM   #9
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Quote:
Originally Posted by polarlyse View Post
...I purchased LED replacement bulbs for our '85 Excella. They had the automotive bayonette mounts. ...???
The LEDs with bayonette mounts will be hard to use, except in an older trailer with those type sockets. You can go from the newer G4/MR11 double pin LEDs to bayonette using adapters, but not the other way around (which would be putting older stuff into newer sockets).

You might look to see if your scare light has the older bayonette socket, othewise I don't have any idea where you might use them. Find an Airstream buddy who has a vintage trailer!

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Old 12-12-2012, 10:46 AM   #10
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Quote:
Originally Posted by SilvrSausage View Post
...The latest generation of LED fixtures with a switching power supply and a wide input voltage range (8 to 30, 85 to 265 AC, wow) solve this problem neatly, but give rise to a new one: they are NOISY AS A PARTY with RFI. Try running the radio or TV nearby and turn them on one by one, they each have their own annoying frequency ...
I took a closer look at the disc LEDs and found it easier to modify them than to modify the socket. (It appears that all the discs are from the same source, but vendors are charging from$3.50 to $11.75 for the same thing, sometimes right next to each other in Amazon ads!) You can see from a comparison of the side and rear pin versions that the power pads are always available for soldering on a small capacitor. You could also solder the cap directly to the power leads.

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Modifying the disc instead of the socket might seem a little odd, but remember, these discs should last your lifetime. I almost don't know why we use a socket--we could solder the disc right to the power wires!

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Old 12-12-2012, 11:35 AM   #11
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I am curious about the RFI problem. Are these LED's 12V or 120VAC? I could see the AC versions making noise but not the 12V ones.

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Old 12-12-2012, 04:44 PM   #12
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I am curious about the RFI problem. Are these LED's 12V or 120VAC? I could see the AC versions making noise but not the 12V ones...
These discs are 12-30 volts DC. See the integrated circuit that's under the pointers on the left disc. This is a PWM (pulse width modulated) voltage/current regulator, so it makes it's own RFI. That's the down side.

The up side is that the disc maintains essentially constant brightness over its wide supply voltage range. There's also four small rectifiers that make a bridge circuit, so these discs don't care about power supply polarity.

Another up side is if you wanted to power one of these over a long wire run. You could feed 24 volt DC to the wire and you could have a voltage drop of up to 12 volts and the disc would put out the same light. I'm going to use that feature when I install driveway lights along a very long driveway. The discs near the power source will have higher voltage, but their light output will be the same as the discs at the end of the wire.

You can dim these by reducing the voltage, all the way down to 7.2 volts, or anywhere in between. They usually draw about 0.2 amps, but hen you get down below about 7.5 volts the current draw is on the order of 0.015 amps and there's still plenty of light emitted for a nightlight.

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Old 12-12-2012, 05:25 PM   #13
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Yeah I was wondering why all the chips for a 12V device. Sounds like they are just the thing for the driveway lights. They don't make a simpler version for the Airstream that won't cause RFI? So putting a cap across the input fixes the RFI problem? I am just now starting to think about LED conversions. I have LED running lights and scare light but nothing on the inside yet.

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Old 12-12-2012, 11:16 PM   #14
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RFI opens another door ... with the factory LED dimmer noise and hum picked up in the radio / TV...dealer has no knowledge of a fix .... and told me to call AS.
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