So, what is this project about? It's simply: to get blue interior lights in a car that has no option for indiglo or reverse indiglo available. This project is for an automatic 1992 Prelude S model. I've tried experimenting with LEDs for Gauge cluster back lighting and it's a real PITA to get right. LEDs are very directional and the beams are narrow. The do, however create narrow bandwidth colors that don't require filtering. They will be used in other phases of this car project but I wanted to try out neon for this one. The idea came mostly from reading about those people that mod their computer cases with window cutouts and neon tubes placed inside. You see, I'm a bit of a gamer and LAN parties seem to be filling up with gamers with crazy case mods. One major producer of these 12v tubes is www.zxmods.com. They had received good reviews from gamer's boards so I gave them a shot. Also, much of the know-how used here was gleaned from various sources on the net and my experience as an electronics technician. As always, my projects are open source to the online community. It was because a few places on the web decided to share their projects with the community that brought this project to what it is now. Enjoy.
This document has been transcribed to be posted here for the benefit of all members.
Warning: The following document is meant to chronicle a project I attempted. This procedure was carried out with care and is by no means meant to imply that everyone can accomplish this project. I realize the risk of permanently damaging my vehicle and take it because the faith in my technical abilities. Anytime you alter the original circuitry, you must take precautions to limit the chance of fire and electrical shock. I must assume that you have taken the necessary precautions like eye safety etc. in addition to this before proceeding with this kind of project.
Let me begin by mentioning that it is a good idea to know how to use the stock wiring harnesses to light the assembly while it is on the workbench. Doing this will allow you the immediacy of testing at the bench rather than taking everything back to the car to see how it works. Also, Ceasar's car would not idle correctly without the gauge cluster plugged in, so the assembly can't just be dropped off until we figure out what caused that. This is not true for the 5th Gen.
Pull out the Speaker grills on both sides. These units have several clips; pulling straight out and forward seemed to work best. Beware of the thin fiberglass support post. On older 4th gens they tend to be very brittle and can break. The grills still stay in without their support if you break them though. (01,02)
Remove the lower rubber trim from below the gauge clusters. It's like a rubber boot; just pull forward. (no pic)
Remove the upper black panel. The screws go in vertically so you'll need a stubby Phillips to get them out. There are about ten or so. After that, the panel comes straight down and out. (02)
Now unscrew that vertical spacer between the tach/speedo assembly and the digital assembly. It has one upper screw. (no pic)
Remove the two screws located on the upper corners of the tach/speedo gauge. Remove the green plugs on either side of the assembly and rotate it onto its back to pull out. Now you can get to the SRS plug on the top of the assembly as you pull it out. (04,05,06)
Disassembling Speedometer/Tachometer Gauges
Remove 5 screws from bottom white plastic plate, and put it aside. The PCBs should pull down and swing out (Watch out for the Capacitors!). (08)
Remove the 6 small machine screws holding on the gauge "motors" from behind. Afterwards you should be able to lift the face with gauges right off. This leaves you with the gauge housing to work with. (09,10)
Remove the indicator housing by unplugging the unit from the green board and pulling back the tabs gently to lift it straight out. (11)
Redesigning the signal indicators Part 1(Our temporary solution)
We used LEDs to serve as our signals and brights indicators. We used some extra ones I had lying around: 2 blue-green 8 candela LEDs with 450ohm resistors each to supply ~3 volts max off of a 12v source. I got those from www.nichia.com and the blue one was from www.hosfelt.com. You should get the blue one from Hosfelt because it is the brightest for the price I can find 6000mcd. Actually, you would calculate the LED voltage drop specifically to each application to get your requisite resistor values: (Fig.A) Fig. AR= V/I = Answer in ohms R=the resistance in ohms (impedance)
V= the line voltage used to power the system (Ours is almost always 12vdc) minus the voltage drop of the LED.
I= the current that the bulb can flow (Most LEDs specify 20 milliamps or .020 amps) Lets say we use a Hosfelt Blue LED. The specs are 2.5-3vdc at 20mA. If V=12-3 and I=.02 then R=450ohms (Fig. B). If you wire them in series (cathode to anode) then you add them to the voltage drop. 4 Hosfelt LEDs wired in series will give you a voltage drop of 12 and this circuit would require no resistor (Fig. C).
Fig. BR= 12-3/.02 =450ohms Fig. CR= 12-12/.02 =0ohms
Also, for the turn signals you can just use one of the factory bulbs with the blue jackets on them to get your light (15).
To use the LEDs in the factory holes you must determine the positive (anode) and negative (cathode) terminals on the gauge assembly that will be the 12v power source. We have them pictured. Each LED is given it's own power because they're specific indicators, not just backlighting.
Solder the resistor to the anode (longer) side of the LED. You need to bend the wires in such a way so that they support the bulb in the bulb cutout of the gauge assembly. There is an art to this and doing it the way I did is not the only solution to it. Just make sure that the contacts are not allowed to bypass the resistor through a short circuit.
Paste on some tinning flux to the copper contacts and the LED contacts so the solder flows on better. I then load up all contacts with some solder (14). Now bring the points in position and solder them in place (13).
Next, you'll need some kind of channel to focus the light forward against the gauge face windows. We cut the acrylic tubes ordered with the neon (for protection) down to 20mm and taped white electrical tape around the outside to keep the neon light from intruding into the channel.
They will need to be focused and seated in place with hot glue or clear silicone because the windows are not directly in front of bulb locations. So far, we hated the outcome. Part II will have us take out that stuff, mount the LED directly against the signal window cutout, and just run the wires back. Surface mounted LEDs will be the object of choice. This will also include some solution for the heads-up shift indicator, which we had to ditch in order to get the most light to flood the inside of the gauge housing (24). Right now that's been taped off (44).
This is pretty straightforward and requires that you identify the pos/neg contacts on the gauge assembly. Refer to the picture to see the labels (18-22). We arrived at these locations by using a multi-meter on the bulb contacts with the wire harnesses plugged in and the parking light switch on. It's also helpful to identify the ground and line voltage wires on the harness to plug those up to a power source while outside the car (ours was purple/red and black/silver).
Test fit your Neon tubes so you can make sure they will fit right and you can feed the transformer supply wires through a convenient opening (17).
Then you can easily wire up the 4inch tubes and starters supplied by www.zxmods.com to the existing bulb contacts to make this a standalone mod not requiring outside splicing and power sources
Securing and Mounting the Cold-Cathode Tubes
After our first test fire, we realized that we would need to remove as many obstructions as possible to disperse the neon light. The emitted light is not very directional, but it does cast shadows (24). We decided to cut all the "reflector fins" from inside the housing and also remove a light fixture that seemed to serve no purpose on this model (26). We repositioned the odometer temporarily to get to some of the other fins (27). You may also notice in the pictures that the gear selector is missing. Well, that is pretty much another phase of the project to be added later. The unit was too big and basically a convenient redundancy. The center console does a good job at letting the driver know the selection. My plan is to fashion a pc board mounted directly behind the plexi face windows. On it will house the resistors and surface mounted LEDs that will take up very little room and keep an array of wires from intruding into the area where light is bouncing around. The turn signals were part of this assembly too and will be addressed in the same way.
Now onto the placement of the neon: Before we fully understood the critical barrier caused by the dot-matrix black printing on the rear of the face, we figured we just needed to put the bulk of the tubes directly behind the tick marks and numbers. Though this was not truly the case, it didn't seem to have any bad effects. Neon tubes are fragile without the protective plexi-tubes so the mounting needed to be secure.
We first determined the best angle for the two neon tubes that would be doing most of the lighting.
Next, we marked the place on the sides of the housing where the tube would extend beyond the walls. We then took a dremel with a rounded cutting bit to carve a notch into the side where they would seat (28).
Once finished mounting the two critical angles, we tested our position before using clear silicone to secure it (hot glue will also work) (29). Be careful on the top left notch because there is a snap there for the cover, which was taken off earlier. Also, the bottom right notch should not allow the tube to come all the way through as it will cause clearance problems and possibly short out on the board mounted there.
Modding the Rear of the Gauge Face and the Needles
With our needles in the optimum position, we then had to give clearance for the left tube. On the back of the cluster assembly there are some "U" shaped protrusions that diffuse light toward the needles. The far left one needle to be ground down, sanded, and buffed to a shine (33,34). Use the procedure listed below to return this to its original luster.
Then we found that the dark spots from the beta tests were mostly cause by what was printed on the back of the gauge faces. They have a clever way of balancing the output of the incandescent bulbs by darkening some sections behind the cluster with a combination of dotted black paint and translucent white paint. We decided to remove everything down to the clear lexan/Plexiglas everywhere there were tick marks or a numbers. Here's the process:
Go over the surface carefully and gently with 320-grit wet/dry sandpaper. You'll be cutting pretty fast through the black dots so just watch what you are sanding.
Now clean up the work with a wet 600-grit paper. Both surfaces need to be damp, but not so bad that water is dripping everywhere.
Now smooth it with a wet 1000-grit paper. You are pretty much buffing the plexi at this point.
Finally, I used a rubbing compound called scratch remover. It acts like a fine liquid paper to bring out the shine in any surface. These last few steps may seem like overkill, but it the proper way to sand and shouldn't be skipped.
Be careful with the areas painted black. That keeps the backlight from spilling in around the windows and cutouts like the SRS, brights, and turn signals (36,37).
Meanwhile, we had decided to clear the needles out with the face was off. This is a tedious process of using many q-tips dipped in basic nail polish remover (or acetone). To allow more access, go ahead and remove the black clips at the base of the needles. You need to vigorously rub the back surface with a clean q-tip (32). Do not soak the needles; only dip the q-tip because the needles like to get hazy with prolonged exposure. We used toothpicks dipped in acetone to pick the stubborn areas underneath the needle center cap. It's a process if scratching, rubbing and rolling the soaked pick in all the painted cracks and crevices. Finally, you may needle to polish the needles with the rubbing compound (Paint scratch remover) to get that last bit of orange stained on there. As with this entire procedure, be VERY careful with these needles, as they are all too easy to snap their tip off or otherwise break them. Here is the final product: (42,43). You can see by the lit photo that we failed to get them to light very bright. If you study image 40 you will see around the needles base is painted black. This seems to be the problem. If correcting that doesn't help, then we're going to reinforce the lighting with LEDs focused on the needles.
Altering the Color Output and Filtering
After our second beta tests, we decided that the blue output was a bit washed out so we decided to employ a bit of secondary filtering (44). The first type of filtering comes from the face itself because the numbers and tick marks are blue. All we did here is use some plastic blue filtering bought at Texas Art supply for pretty cheap. The face was laid on top of the sheet and traced out. The template was cut to size using an exacto-knife. Make sure the blade is new. You'll want to trim it in such a way that the red on the tachometer is not covered, that it is not visible through the odometer and trip log windows, that there will be adequate clearance for the gauge face to lie flat when it's in place, and the alignment holes are big enough to clear the posts (38,39,40). We burred out the holes with a dremel tip. The high bit speed allows the surface to be cut without grabbing and twisting this fragile material. Now reassemble the face and see how it looks.
Do the installation in the reverse order. The main thing to remember is to snap the shield/cover on first. It is almost impossible to put on once you put the two boards in place and screw on the white plate. You will now have three transformers dangling around. We used the supplied wires, but you can use longer ones so that they don't get in your way during reinstallation. Putting the cluster back in is a PITA without adding the neon power supplies to the back. The best place for them to sit is in the pocket above the cluster once it's in place.
Lessons learned and future plans:
Four neon assemblies would have been the best setup, but our budget didn't allow for it. The needles need to be redone because they are not bright enough.
Our future plans is to do the turn signals and bright lights indicator as well as do up something custom with the heads-up shift indicator. They can be done with surface mounted LEDs on a board, but it's not too bad since there is a shift indicator on the center console. We intend to do the EL gauges on the passenger side, the climate control, and CC shift indicator. Until then, we welcome any comments or recommendations to this write-up. I am available on www.preludeonline.com,forums.hpoa.org, or www.houston-imports.com under the screen name pIOUs. Thanks.
i hate to say this but it is a repost. it is till a cool thing and last time it was linked to a webpage with all the info so this is nicer because it can be faq'ed.
Originally posted by brendon2k i hate to say this but it is a repost
Actually it's not. The original post (from months ago) was a link to another site where this writeup was located. I lost the host and when people wanted the lost info, I posted it here. You will not find this anywhere else on the net. I wrote the original, and I am posting it here. The only thing reposted was the picture of the results.
Originally posted by MR.CLIFFORD nice write up. The link just has one picture in it of some under body neons??
Is that going to change?
Yes. As soon as I find the original install pictures. Please be patient with this. Fact is I may never find the pictures. You will know when I find them because I will insert them within the document. I had to put something inside the album to create it.
Originally posted by pIOUs
Actually it's not. The original post (from months ago) was a link to another site where this writeup was located. I lost the host and when people wanted the lost info, I posted it here. You will not find this anywhere else on the net. I wrote the original, and I am posting it here. The only thing reposted was the picture of the results.
so you are saying it has not been reposted but you posted it again? well it is useful that it is not linked now but it is the same information, correct?
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