digital voltmeter in dash project (pics)?

i was thinking of putting a digital voltmeter in my dash, specifically here, in the middle piece:

in case you cant see the images, here are the links:
http://www.spymac.com/upload/gallery/user_20795/medium/upload_82622.jpg
http://www.spymac.com/upload/gallery/user_20795/medium/upload_82624.jpg
http://www.spymac.com/upload/gallery/user_20795/medium/upload_82399.jpg
http://www.spymac.com/upload/gallery/user_20795/medium/upload_82621.jpg

so there's the location- i could probably cut out a hole for the voltmeter in the plastic removeable piece, and wire it in there somehow...and the great thing is, if i made a mistake, a new dash piece is probably like a buck...so what do you guys think? do you know of any sites for really really small voltmeters?
here are some ive found so far, but im not sure if they'll work or if they'll fit...

this (no backlight, but cheap):
http://www.martelmeters.com/products.php?cat=4
or this- the first one listed- (nice red color):
http://www.redlion.net/products/digitalandanalog/digitalpanelmeters/dcvolt.html
both of these would work, correct? do i want a DC voltmeter or what...?

here is the list of voltmeters that a site carrys (search for "voltmeter"):
http://www.digikey.com
i need one that is as small as possible...
so what do you guys think? good idea? how hard do you think this would be to do? any suggestions/help would be great b/c im gonna need some ideas...

Nate, whenever you post a pic I never see anything, not even a red x.....

Is the voltmeter backlit??

pics look fine to me...

..the second voltmeter i listed is red and looks backlit. the first one isnt backlit but is cheap. www.digikey.com has a list of them, some of them even have green backlights which would match the rest of the lights in my car...the only problem is that they dont have any pictures and sizes of the voltmeters...

I see them on my wifes computer. My internet firewall on my computer must be set too high.

Nate, that piece is the same I modded. But that back support needs to be cut out. I used a hacksaw to cut down the short sides of that rectangular box back there. That opened the entire length of the insert.

If you take the entire instrument cluster surround off (three screws in those inserts, two up by the cluster) you'll see you have a lot of room behind that piece.

Good Luck!

N.

ok i just cut out the rectangular piece in the back using a razor...not too hard...thats all you cut right? you didnt cut the 2 long clips off, right? and what did you use to cut the front of the piece, a dremel?

No those two long pieces secure it to the dash.

I don't have a dremel (my birthday is soon....hmmmm)

I used a tiny drill bit and went around the perimter of the rectangle I had scratched into the surface of the piece. Then with the razor knife I cut between each little hole. It's a messy way, if you have access to a dremel I'd do it. But you need to start the hole, and a drill with a small bit works best.

Nate, I'm posting pics of the working lights here soon. Keep your eyes open.

Not sure about them measurements but I would go with:

i actually found one on digi-key that has a 18mm tall cut out, should be ALMOST right...it comes in green with a backlit lcd..
http://dkc3.digikey.com/pdf/T041/1254-1258.pdf
CDPM731-ND or CDPM733-ND
if it doesnt fit exactly i can always trim the clips a bit..the drill bit method is a good idea, since i dont have a dremel either.
ok so to make this work now, what do i need?
do i need these (this is what my friend is telling me):
+5V regulator
a 27k and a 3k resistor

Looks good. I think it'll fit, but if you cut too big a hole the piece will be pretty flimsy. But if you cut it, insert the V meter and glue it in, that should provide enough support.

Good luck!

alright...i trimmed it down a bit, im pretty sure it will fit. anyways, the only thing im worried about is mounting it...the front of the dash piece is curved, as you know, and the lcd and trim piece are straight...so do you think it will look ok when mounted?

Wait, you're mounting it in the plastic insert right? Tha piece is straight.

There's the spot with the trim removed.How deep is the V meter? I think it'll be flush, or flush enough that it doesn't matter.

Have you bought the V-meter??

yeah, im mounting it in the little dash insert piece, like you did with your switches. its not EXACTLY straight, which is why im just a little worried of how it will look when finally mounted, you know what i mean?
i havent bought it yet, im not sure of the depth, the diagram in the pdf file i posted is kind of hard to read...

Hmm
This one is too big

The cutout for is is too wide, according to the .PDF sheet.

hmm..i just realized- it looks like the one that would work best has a lcd face that has a height of 18.3 mm and the circuit board behind it has a height of about 26mm or something...it will fit in the dash hole, but i'll have to cut off one or both of the clips, and then secure the dash piece in there by gluing it...

hmm..here's one that would definitely work without cutting off the plastic clips, its very small

not sure about how it looks though...

This fits...
Nate, what size hole have you cut? I'm holding the dash insert right now.

yeah, im looking at it too...the height can be at most around 18mm-19mm maybe, in order to fit between the clips. i just like the green one b/c it matches the rest of the lights..
the cutout height of the green one i just had a pic of is like 11 mm, length is 28mm. outside trim is 14mm height, and 30 mm length

Looks like 11/16's an inch between that or 17.5mm. That second gauge (the black & white one) should fit no problem between there.

I'd hesitate to remove the clips since you may need to get back there from time to time, gluing it on may be a bad idea....

yeah, i think im going to go with the green one that i just listed a pic of. its very small and will fit fine, and also has a built in regulator...so now, i need to know how i can wire this. (i still need to order the voltmeter sometime, probably wont happen for another 2 weeks or so).
here is the one i think will work best:
http://www.martelmeters.com/products.php?cat=3&action=detail&id=8
http://www.martelmeters.com/pdf/DPM_1AS-BL.pdf

ok so first of all, how do i wire that to my car? i need 2 resistors, right? someone is telling me i need a 27k and a 3k resistor..is this right?

also, how can i physically wire this, meaning, am i going to have to take off the whole dash piece in order to do this? how do i take it off?

Nate, sent you e-mail
No idea on how to wire, but removing the cluster surround is easy. 5 screws. Two under hood by the gauges come out easy with a long phillips. They are angled so no twisting necessary. 3 are hidden under the plastic inserts.

Remove fog light piece & unplug, plastic insert next to that hides a screw.

Remove defrost & unplug, another screw. Remove clock and that little piece next to it, last screw.

Then the cluster surround pulls right out as one unit. You'll have plenty or room to spare.

About the wiring, that's outta my league...

The datasheet for the voltmeter should tell you what resistors you need for it (and how to hook them up) based on what your intended voltage measurement range is. You probably want to use the 19.99 volts range since it's got a 3 1/2 digit display (ie, 1999).

As far as where to connect it...for best accuracy you might want to run a wire directly to the battery positive terminal. If you don't care about accuracy, then just connect it to the clock or radio power wire.

You're also going to have to use a 7805 voltage regulator to power this meter--it won't run off 12V without a negative supply, but it will run off 5V without one.

The 7805 regulator is a three-terminal device available at RadioShack for about 99 cents that takes 12V in and outputs 5V. The third terminal is connected to ground. You won't need to heatsink it for powering this meter. I would solder three wires to the 7805 and then stick it in some heatshrink tubing and shrink it down. Use the TO220 package 7805--this is the only one RadioShack sells.

The resistors needed for a 19.99V full scale reading are 1megohm and 10kilohm. I would recommend the use of 1% tolerance resistors for the greatest accuracy, but you will need to calibrate the meter. I would suggest calibrating it against a digital multimeter.

You will also want to connect the XDP terminal to the DP2 terminal so that the decimal point is in the correct place.

ok, this is SORT of making sense. so i DO need a regulator? also, on that pdf sheet under "applications" there are a bunch of circuit diagrams listed. which one should i follow when i install it?
and damn, i dont have a multimeter...

I got one from the Jegs catalog that plugs into the cigarette lighter, since I don't smoke it works out for me.
Plus I can take it out when I want to and didn't have to modify the car.

Originally posted by Rizzo:
I got one from the Jegs catalog that plugs into the cigarette lighter, since I don't smoke it works out for me.
Plus I can take it out when I want to and didn't have to modify the car.

can you show me a link? i just think it would be a fun project to do something with that blank panel

and a LCD display there would be pretty cool