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Discussion Starter · #1 ·
Well, we all know that the stock 7440 (21w) backup lights are pretty dim, and there are few solutions available.  LED's don't throw enough light.  PIAA 27w blue bulbs are not much, if at all, brighter.  The clear Raybrigs are at least noticeably brighter, and brightest yet would be the dabears2k HID system.

Being a general cheapskate, I decided to assemble my own bulbs from components.  The inspiration came from http://www.skidmore.edu/~pdwyer/e/backup_bulbs.htm  Luckily, autolumination.com offers a 7440 blank base for custom LEDs, and they were suitable for this project.  The cups were taller than needed, especially for use with a hot incandescent bulb, so I trimmed them down a bit:




Some wire from a smallish paper clip provided the leads.  The bends are spaced about 0.45" apart, and the bend radii are about 0.080" (a piece of weedwacker line or something of similar diameter, held against the wire, helps to make these bends):




This is how they look installed.  The tops of the wires needed to be trimmed down to help make room for the new bulb:




The new bulb is a bi-pin halogen rated at 35w with 12v.  This is equivalent to those used with the 894 bulb family, and puts out almost 50% more lumens than the 7440.




I had originally planned to solder or at least crimp the connection in some way, but ultimately just press-fit the bulb terminals in parallel to the connection wires and then filled the base with some epoxy.  This is how it looks next to the stock 7440 bulb:




There isn't much room in the Mazda reflector housing, so you have to watch the overall height of the bulb.  I originally ran these for 3-minutes straight with no problems to the housing, wiring or connectors.  They still work fine after about 3 weeks of normal use.

Are they brighter?  Yes.  Is it a huge difference?  No, just an improvement.  I doubt that the reflector housing was truly designed for efficiency, thus compromising the aim and throw of any bulb.  Unfortunately I have no worthwhile before/after lighting shots since my photography skill and equipment aren't yet capable of producing a good objective comparison.  I'll post them later if I can get it right.

I may try some other bulbs, perhaps even blue ones, although these would be for appearance rather than performance.
 

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Discussion Starter · #3 ·
[quote author=Cys063S link=topic=137732.msg2969536#msg2969536 date=1235959136]
Great idea, where did you get the bulbs from?
[/quote]

They are sold by various internet "bulb" stores; I just happened to find some from a store that sells them on ebay for a couple bucks. Just search for the particulars, and they will come up. Originally I had planned to buy some of the various 37.5w (which is the power you get from a 35w bulb running at 12.8v instead of 12v) headlight bulbs and hack them up. For blue bulbs, that's still pretty much the only option.

The next step up in power with this bulb type is 50w - I'm not sure about pushing the system that far.
 

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i was starting to wonder what happened to you after a while. :)
glad you went through with this and made a nice write up.
if you have a tripod for your camera, it will make it easy to take night pics of the reverse bulbs lit up.
 

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Discussion Starter · #5 ·
[quote author=NoRegrets link=topic=137732.msg2969833#msg2969833 date=1235967371]
i was starting to wonder what happened to you after a while. :)
glad you went through with this and made a nice write up.
if you have a tripod for your camera, it will make it easy to take night pics of the reverse bulbs lit up.
[/quote]

Yes I'm still here. :) I have a tripod and would probably need set the timer for the best focus with no flash. Is there any trick to ensure that exposure setting stays the same between shots? My camera is nothing fancy, just point-and-shoot.

You still happy with the Raybrigs?
 

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the raybrigs are definitely doing their job. much better than the stock bulbs.

all i did when i was taking the night shots was turning off the flash option and keeping the tripod/camera in the same position for the before and after pics.

most of the time, the camera will make it's own adjustments for the shutter speed.
 

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Discussion Starter · #7 ·
Thanks, I'll try to get back out and snap more pics, maybe this weekend. I'd also like to set up some sort of object array to get a better idea of the relative lumination of the different bulbs - perhaps something like parking lot markings.
 

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Finally I found this thread again. For the bulbs, just go to the Depot and hit up the Low Voltage out door lighting asile. There are 35 and 50w bulb 2 packs for $7. I wonder if the plastic holder can take the heat off the 50w. If I do them Id run them off a relay and tap into the 2G stero power line. Just thinking out loud!
 

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very cool......i have an idea. since the reflector of the back up bulb blows how about trying to make the bulb glas a reflector? use some tape and wrap it around the top 1/2 inch of the bulb. then use some high temp chrome/silver paint and paint the rest of the bulb. this will reflect the light out the front of the bulb (obviously remove the tape after painting).......or make the bulb so hot it catches something on fire. i am in no way sure of the safety of this idea but you could try it out of the housing connected to a battery for an hour or so to test it out.
 
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