Heads up Display?
 

For a HUD, I think you would want to use a bright LCD that inverts the image (i.e. green numbers on black background). And a bit of concave mirror will correct the image and allow you to scale it up.

http://img526.imageshack.us/img526/5...micshudlk0.jpg

Never tried it myself however.

Cool, I guess it is more appropriate to have my own thread than continuously hijack the OBDuino thread. I was thinking the exact same thing about using a reverse polarized LCD with a bright backlight. Either that or a Vacuum Fluorescent Display but those are much more expensive so I'm hoping a reversed LCD will work (I can reverse the polarizer myself, have been doing it with cheap calculators to make sure it works). Right now I have just been using my cell phone to "prototype" the set up. I have experimented a bit with a cheap fresnel lense and can "project" the image on a plane that is perfectly vertical instead of reflected on the slanted windshield. Due to the small width of the screen, distortion due to the curved windshield doesn't seem to be a big issue, however ghosting is. Have gotten some ideas from a thread on mp3car.com. Not sure I will be able to get the image projected out in front of the car though.
Zac

I thought that was a really cool idea when I read it in the other thread. I encourage you to try it and post pics!

I encourage you to try it as well! Also, separate threads are good, since I'd stopped following the obduino thread, and wanted to see this, ;)

I had to do a quick experiment with a makeup mirror too, and a short extender cable :) It is promising, it is brighter in real life and the lcd is currently limited to half brightness (and might be pulse overdriven to a brighter appearance). A LED array might not be a bad idea either, but complicated.

http://opengauge.org/diympggauge/hud1.JPG

http://opengauge.org/diympggauge/hud2.JPG

So you reflected the upside down lcd onto a mirror and from the mirror to the windshield? Not a bad idea but I'm hoping to use the software to reverse the LCD, reflecting the image only once (onto the windshield) should maintain a higher brightness than multiple reflections. I just read a little about OLED displays (as they are available with the proper driver) and they are supposed to have significantly greater brightness and contrast than an LCD with a cost much cheaper than a VFD. The cheapest I have found a 16x2 VFD is $65, found a 16x2 OLED for $25 on ebay. I am certain that even a backlit LCD will work at night but I think it will take something brighter with higher contrast during the day. Right now the only backlit LCD i have is my cellphone and its difficult to read in bright daylight driving conditions anyway.

From my experience with OLED backlights, they are not that bright and don't last very long. Normal LED backlights or even CCFL backlights are a better bet.
BTW, the OLED-backlit display I have cost only $8 from a local electronics parts store and it's a 2x24. I would not recommend it, of course, as the OLED backlight became unusably dim after just 4 years while the normal LEDs had no noticeable aging in the same time period.

yup

One thing I haven't mentioned about trying to do it in software is that the lcd character generator is all fixed (except for 8 customizable ones). There is no reasonable way to reverse/flip the bit patters for the standard character set so "TANK MPG" will be upside down in the big display, as will all standard characters. But if you are doing all big block numbers then you have control of the arrangement of the "blocks" there and can generate an upside down image. Maybe with a flash of the screen abbreviation when you press a button (up to 4 chunky letters).

Also, regarding brightness, a single mirror isn't losing much, especially compared to the windshield. Though it does add some bulk, cost.

I loved the heads up display in some of the GM cars. I wonder if you could use one of their assemblies and adapt it to this. Might give you a few more ideas on what works in practice to look at too.
http://www.ranrich.com/gp97hud.jpg

What a great idea - nice pics, dcb!

Maybe the following can be adapted to a HUD? Simply shine the light through from the front side of the upside down lcd?:)

Projection clock

FYI, mouser had a 2x16 VFD for $38, interface looks similiar at first glance (with synchronous serial option available too).

M0216SD-162SDAR2-1

I'm kinda tempted to stop by newhaven and pick one up :)
http://www.newhavendisplay.com/pdf/m...162sdar2-1.pdf

An inexpensive graphical VFD would be nice too, no mirror required. But an additional $38 is pretty cheap for custom HUD mpguino that takes little to no extra programming :)

on the LCDs, could you just switch the pins that are getting excited to be reversed?

Seems the mirror trick would work rather well with the reverse polarization of the LCD to do bright characters / dark background...

To reverse an LCD you use polarizing film mounted at 90 degrees to the original orientation

Sort of. There are two polarizing layers, one behind the LCD glass and one in front.

First you have to cut the top layer off, or tear down the LCD and strip off the top layer.

Then you have to find replacement polarization film, or cut your original to fit.

But then in your HUD you will be shining blue light in your eyes, which is like the worst color for night vision.

I'm not sure which plane will be polarized at that point but you would want to avoid vertical for glare reasons. The bouncing off the windshield should give it some horizontal polarization which would attenuate the image if it is vertically polarized from the LCD.

My plan
 

I think the ideal HUD color would be red. So to that end, maybe just a 3 digit large LED numbers and a small mirror would be a good experiment. Ideally it would be a first surface concave mirror to reduce ghosting, but it would have to be enclosed if used for long.

Perhaps using an atmega168 to drive the LED numbers and read the serial output from a mpguino, a-la remote display. Haven't seen one of those materialize yet (unless you count daisy chaining mpguinos).

I did pick up a couple some LEDs from the local sciplus.com for $0.75 a piece (they quickly ran out of stock), and picked up the largest stick-on convex mirror I saw at the store (couple bucks) and carefully removed the plastic. The trick now is to strip the tan stuff off the back of the mirror (paint stripper?) and I should be left with a first surface concave mirror. And of course some electronics/wiring/programming to sort out.

http://opengauge.org/diympggauge/hud3.JPGhttp://opengauge.org/diympggauge/hud4.JPG

It isn't a priority for me at the moment, but if one or more of you think it is a good plan and feel reasonably confident you can pull it off, then by all means help yourself. Let everyone know how it goes and if you get stuck.

totally subscribed to this thread. always dreamed of doing this, never had the motivation. good luck!

how about some pictures of real-world HUDs?
Found these on YouTube. Not mine obviously. I'm not sure what he's using, but I'm sure we're all interested in a more integrated approach - not something sitting on the dash. Plus, I would want the display a bit closer to the hood level, not hovering straight ahead, maybe that's just me though.

http://www.youtube.com/watch?v=s5w9m...eature=channel

http://www.youtube.com/watch?v=UBKH5JxgD5M&NR=1

I recently purchased a digital alarm clock, and plan on gutting the LED screen for use with a MPGuino-type setup. I'm looking forward to working on it!

Looks good:thumbup:

It's too bad it's against the law in most places to put tint below the first few inches of the top of the windshield. A super light tint would remove most of the double image your getting from the display. I tried the trick with my cell phone in my Jeep. Works great with the tinted windows.

Yeah, I think what is also contributing a big deal to the double image being a problem is the size of the numbers that display uses. I plan on using a bigger display, so hopefully the double image won't interfere as much.

I have most of the stuff ordered for the mpguino/heads-up-display. Can't wait to get started.

Larger number will probably help a lot. Less overlap that way. I guess if it does end up bothering you you could pull the fighter plane trick. Have another panel just before the windshield that has a semi-reflective surface. Technically that way your not tinting the windshield. Don't know if that will get you around all the laws or not.

:thumbup: This is a total drool fest!! :thumbup:

So, I had somewhat of a moment of realization...

Problem #1 - Cannibalizing a Clock for its LED Display
I got my clock which i had planned on using as a seven segment LED source. I took it apart, and as I suspected, it has a single integrated circuit running the whole display. To my surprise, any given input to the LEDs will light up two LEDs - not just a single segment of a number. I suppose since the tens-of-minutes digit only goes to 5 and the tens-of-hours digit only has to display 1 it's no big deal.

Problem #2 - Brightness
There is a plastic, tinted cover over the display, and a translucent, red film over the LEDs themselves, so when those are removed you have a very bright display...but i don't think it's bright enough still. I'll have a chance to find out this afternoon when i can take it out in sunlight. But I think the solution is going to have to be a custom seven-segment display in order to get the size of display I want (I would like bigger digits than the LCDs can offer).

Problem #3 - The double image. I just plain can't deal with this. It looked good at night, but it still bugged me...
And I was hoping to stay away from this, but it's looking more and more like an inevitability. Hopefully, I can just have a cantilevered piece of plexiglass in order to maximize visibility.

Anyway, parts are going to be getting in soon for the MPGuino, so I'm pretty excited.

I managed to get the backing off the mirror, but the range of angles was so picky as to be impractical. So I tried a chunk from another project. It shows some promise as an inexpensive and simple HUD as well (might need brighter LED and/or smoke cover, non diffuse LEDs might make more sense too):
http://opengauge.org/diympggauge/huda3.JPGhttp://opengauge.org/diympggauge/huda4.JPG

http://opengauge.org/diympggauge/huda1.JPGhttp://opengauge.org/diympggauge/huda2.JPG

I ordered about 60 narrow-angle, non-diffused leds from superbrightleds.com last week. Hopefully they are powerful enough for use in daytime.

Non-Diffused LEDs
 

SUPER STOKED!!

So I received my non-diffused leds from superbrightleds.com. They're red 5000mcd 15deg 5mm LEDs. THey have a nominal voltage of 2.1V.

I hooked six up in series and wired them to the battery (car was off, so 12V give or take) I'm happy to say that the reflection off the window was too bright to look at (OUCH!), and that's at 2.0V, still got a decimal to work with!.

That was at night however. The real test will be in the daylight, and hopefully I can have a diffusing layer on top of them without losing visibility in the daylight.

OK! I made this diagram. Hopefully it will be pretty self-explanitory.

I plan on having two separate layers. The top layer will have a seven-segment number pattern in it (made out of mdf, cut on a scroll saw). The bottom layer will have holes drilled for the LEDs in a pattern that puts two LEDs under each segment of a number. The seven-segment number layer will be a bit thicker than the hole pattern layer and the whole assembly will be painted flat black in order to minimize glare. As mentioned I want to have a diffusing layer positioned in-between the hole-pattern and seven-segment layers. It might be as simple as a sheet of copy paper, but we'll see how bright these are in the daylight.

P.S. I forgot to mention that I also received my white on blue LCD screen and my binary-to-seven-segment ICs (74LS47's) in the mail today. THis project is gonna rock!

Good news:
The LED reflection is too bright to look at in full daylight, and covered by a sheet of paper, the light is definitely visible

Bad news:
My original plan to have a cutout of the seven-segment digits is not going to work. I drew up a custom seven-segment design in AutoCAD, printed it out, and was cutting it out on a scroll saw. I was getting pretty good results on the top, but on the other side, the lines were pretty wavy.

So now i'm considering what to do. Maybe I could take the patter to a professional print shop and get a transparency made? I'm also considering scaling the numbers up just a bit and using straight edges of aluminum foil to screen off a pattern.

Any ideas out there?

Use a flexible cutting board from the kitchen dept. They're like 1 or 2 mm plastic. Use tape or something to mark off the segments, then spray it black. It'll diffuse nicely, and be opaque everywhere else - as well as cutting brightness down a little.

That sounds like a pretty good plan.

Walmart.com: Progressive Color-Coded Chopping Mats, Set of 6: Kitchen & Dining

Little pricey in my opinion. I think the dollar store here where I live has generic "white" ones.

I came up with a dirt cheap option that has yielded some pretty good results.

I took my number template (attached) and secured a strip of clear packing tape (sticky side up) on top of it. Then I cut small strips of aluminum foil and progressively covered sections of the pattern. After I was done I covered the foil side of the assembly with another strip of clear packing tape.

I really wish I had a camera here because this came out really well with really crisp edges . I'll try to get pics up asap.

I have a spare sheet of Plexiglas that I'm gonna sand down for a diffusing layer.

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...huh?

I know this is not what you all are looking to do, just giving you all a heads-up. I've got this HG100 GPS HUD in my car so I can keep a close eye at the speed at *all* times without needing to glance at the speedometer all the time. This works quite well even in the daytime, and I didn't bother using the supplied tint. This helps me to keep my speed constant, thus increasing MPG slightly. This is bright enough that they had to put in a light sensor to dim the display when dark. I brought this for about $60. This also has a bluetooth link so I can use this with other things such as mobile phones etc, and the display can be turned off. Well useful gadget, and I'm very impressed with it. Chinese designed and built, but very good quality, better than most stuff I've seen (Euro made, US made, whatever). Even the packing was the best I've seen, I felt quite guilty to put it in the recycling bin, wanted to put it on a display shelf! This originally cost $150 which *is* far too excessive, but $60 is a lot more reasonable.

Unfortunately, this doesn't have MPG info, which is what we all want, eh!

Well, technically it works on the same principal with the hard edged diffused LED display. If you find a busted one and hook up to the Guino's serial output, you're all set :-)

Instead of trying to add layers/distortion to reduce brightness, has anyone tried using a potentiometer as a dimmer switch ?
Reduce V IN and output will drop accordingly. I used to make LED annunciator panels. To get the clients attention where it was more critical we used different values of resistors. The rule is you can overdrive the LED until it gets warm safely. Run the voltage up until it gets hot(very briefly), back down until its only warm, then measure the ohms of the pot. Place a fixed value resistor of that value inline with the pot and it will prevent the hand on the pot from blowing anything.
Keep us posted !!!!

Any word on the finished product and photos?