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Discussion Starter · #1 ·
I have several Malibu lights used as structure lighting for the layout and they work great.  The bulbs are all 12 volt and range from 4-11 watts.

What I'm looking to do is add a lighted gas pump globe to this Malibu electric line.  But a standard Malibu bulb obviously won't fit in the globe.

I'm looking at possibly using some HO 12 volt bulbs I have from Miniatronics.  However I've never really had much luck using non Malibu bulbs with their power pack.

I've tried using 18 or possibly 16 volt miniatronics style bulbs for use around a gazebo.  But they were barely lit off of the 12 volt supply.  Now it could be that these bulbs were dim because they were rated over the 12 volt supply.  But it seems any bulb, other then a Malibu, on the line doesn't light up much.  My theory is I need at least a 4 watt bulb to have any significant brightness off of the 12 volt Malibu transformer.  Miniatronics website lists their bulbs as 12 volts, and 50 milliamps.  So if watts = amps x volts, does this mean the minatronics bulbs are 0.6 watt bulbs (50/1000 = 0.05 amps)(12 volts) .  My electric and physics knowledge is very limited to high school and I haven't done any calculations since then.  0.6 is a big difference between 4 and could be why they are so dim.

So before I wire up the gas pump globe with a 12 volt bulb, are there any suggestions on what to do?  Is wattage that much of an issue with Malibu wiring and transformers?  And I also don't want things getting too hot in the globe so perhaps leds might be a better solution...but then I get into viewing angle and resistor issues.

Uggg, electricity can be a real mystery /DesktopModules/NTForums/themes/mls/emoticons/crazy.gif
 

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Look for 14v grain-of-wheat bulbs. This is a common voltage in HO and they light quite nicely from a Malibu transformer.
 

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Radio Shack has some miniture 12v bulbs in white, amber, green, and red.  Also your might try All Electronics for their "grain of wheat" bulbs.
Notice bulb under the eves of the station.  It would probably work inside your gas pump globe.


Jim C.
 

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Incandescent lights have an extremely narrow range where they work properly. These aren't bright because the voltage is too low. Nothing to do with Watts.
 

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Matt,

What wire are you using leading up to the bulb you are using. If you are only running a long length of 18 ga. wire up to them, there could be a big voltage drop. Its easy to check with a volt meter. A bump up to 12 or 14 ga. low voltage landscape wire could fix the problem. Also, larger landscape light transformers will have multiple voltage taps like both 12 and 14 volt feeds. Using the 14 volt tap can help compensate for voltage drop.
Also, I did not ask what else you are running off that transfomer. If you are getting near the max wattage output of the transformer that will affect performance. I like to stay well within 80% of the listed max wattage

-Brian
 
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Posted By Torby on 03/05/2008 3:44 PM
Look for 14v grain-of-wheat bulbs. This is a common voltage in HO and they light quite nicely from a Malibu transformer.

I buy mine from Dave Goodson-TOC...he always has some laying around to ship!:)
 

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Discussion Starter · #9 ·
Good suggestions here, thanks all.  Looking at how easily many of you have used non Malibu bulbs off of the same power means I must have used an 18+ volt bulb when testing in the past.  Not sure where it came from, but it is similar to the bulbs found in the USA roadside shanty.



Brian,

I'm not sure what wire this will be hooked up to yet since the building isn't built yet.  But my feeders are all off of thick Malibu wire, so I haven't had much voltage drop from wire.

The transformer is  300 watts.  Only Malibu bulbs off of it so far.  We're not over the 300 watts yet.
 

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I'm not sure, but the Malibu lights may be 12v. AC.  If in fact they are alternating curent, the rapid polarity changes would significantly shorten the LED life, even with a 1000olm resister.
JimC.
 

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The output of these transformers vary quite a lot: (exerpt from the Mailibu web site):

Q: What does the statement "First fixture must be 10 feet from power pack" mean and why?

A: You must have at least 10 feet of cable between the first fixture and the power pack to avoid premature bulb burn-out.

The output will vary according to load, lightly loaded you will get about 16 volts in my experience.

Regards, Greg
 

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That's 'cause it's just a transformer. You remember those old things made of iron wrapped with wire?
 

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San I have use 14 to 16 volt grain of wheat bulbs with this system and they are quite brite.  I use them to light up a lot of bulding and swich stands and have been in use for over four years and not problems.  Later RJD
 

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Thanks Tom I knew that! /DesktopModules/NTForums/themes/mls/emoticons/tongue.gif I'm trying to help people understand the variability of the transformer output based on load.

I thought the quote from the manufacturer would lend credence. When they tell you that you can burn out bulbs, it makes the situation clear...

Regards, Greg
 

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"signicantly shorten" as in POOF!  LEDs are only good for about 6V in reverse, the Malibu transformer is putting out AC much higher than that.

I have used LEDs successfully with Malibu-style power packs, but I am a professional.  Anybody who puts "electricity" and "uggh" in the same thought should probably stay away from LEDs in this situation.
 

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Yep, was not going to go into PIV ratings yet! Still struggling to get the concept of load vs. output voltage on a transformer!

Do you usually add another diode with an appropriate PIV rating?

Regards, Greg
 
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