LCD Dashboard Ponderment

**Vchat20** · 01-13-2009, 03:43 AM

Now I have read all the previous attempts and theories posted around here on the idea of a full digital/LCD based dashboard replacing the classic analog dials and whatnot. I'm fully aware of the different roadblocks and whatnot.

I got the idea for this earlier today after staring at one of my keychains and have been mulling over the details in my head all day. The keychain basically consists of a small single segment LCD powered by a small calculator based solar panel and switches on and off every second or so. Behind that panel is just a small printed piece of paper and what happens is that when the LCD is powered, it goes completely opaque. When it goes off, it's completely transparent.

Now the biggest downside of this whole idea is somehow making the digital display, that is being added on in this case, fully viewable while hiding the dash behind it. In light of availability of electrochromic foil or plexiglass in easily acquirable fashion, there are a couple possible solutions:

a) Interface with the dashboard lighting and switch it on and off on demand to cut down drastically on light bleedthrough.
b) Use a large size TN LCD panel that will fit the dashboard with preferrably the fewest segments possible (finding a traditional computer display of this size would be cumbersome and pricey and interfacing with something other than a traditional display output would be near impossible) to the effect of being able to switch it on to block light going through and turning it off to allow light again.

Combining both (a) and (b) would probably combine to be most effective really.

That brings us to the actual digital gauge display screen. That would be the fairly easy case of an LCD panel sans backlight and opaque backing material placed over the previous LCD used as a light block. Lighting up this puppy would be another issue. MIGHT be able to get away with some high power LEDs between the first (light block) LCD and the second (image display).

There is also product from Plexiglass called Endlighten which is commonly used for the different multitouch tech demos out there (Microsoft Surface is one prime example) which can diffuse the light through LEDs on the edges but allow you to see through it clearly. That is also a possibility and can be placed between the two LCD panels.

So all in all we have this:

Analog gauge dash
\/
Large single segment TN LCD
\/
Plexiglass Endlighten\LED
\/
Display LCD

With the complexity of this, it would probably be smart to use some form of PIC to interface everything but the main display LCD. Interface with the power going to the analog dashboard lighting, control the power to the light blocking LCD, and control power to the LEDs attached to the plexiglass. Then interface the PIC with the computer. At this point you could have the computer send a single command to the PIC which would then cut the dash lighting, opaque the first LCD, turn on the LEDs, and switch on power to the display LCD in one single go. Another command can do the reverse: turn off the display LCD, turn off LEDs, turn off the 1st light blocker LCD, and cut back on the dash lighting. With more work, the PIC could default to displaying the analog gauge dash and only run the digital display if there is a constant signal coming from the computer saying so.

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This is merely a theorhetical and brainstorming type of deal. If anything, it's in hope to spark thoughts in the rest of the bunch here and see what comes out.

I'm sure the idea could use tons of improvements, but it's a start.

**Sicarius** · 01-13-2009, 01:59 PM

Why get all complicated using a PIC? Couldn't you do all that just using a standard automotive relay?

Hook the dash lighting to the NC contact (87a) and the light blocking LCD, LEDs and display to the NO contact (87). Control the coil with DTR from the serial port with a simple control program and Bob's your uncle.

**2k1Toaster** · 01-13-2009, 03:28 PM

Originally Posted by Sicarius

Why get all complicated using a PIC? Couldn't you do all that just using a standard automotive relay?

Hook the dash lighting to the NC contact (87a) and the light blocking LCD, LEDs and display to the NO contact (87). Control the coil with DTR from the serial port with a simple control program and Bob's your uncle.

If you do it that way, you should use either a smaller relay to switch the larger one, or a transistor to protect your serial port. Also some other electronics are needed to deal with the huge spikes a relay can cause when they shut mechanically.

Also I havent even seen a mobo with a serial port on it in ages. Same with a lpt1 port.

**Sicarius** · 01-13-2009, 04:07 PM

True enough; some protection for the serial port would probably be in order.

As for the motherboard ports, my Intel D201GLY2TA has both serial and parallel as does the popular D945GCLF2.

Of course, another option would just be to go with a Fusion Brain.

**Vchat20** · 01-13-2009, 04:44 PM

Well, the only downside to going REAL simplistic with just relays and all is the need to control the brightness of the LEDs since these now become the backlight. Would probably have to do some PWM handywork through the PIC. And at that rate, could probably do a usb interface on it.

Or on the other flip of the coin: Do Sicarius' earlier idea doing simply relays and do those off the fusion brain and could set up a simple PWM circuit that defaults to full brightness and can be triggered to dim through either another output on the fusion brain or an illumniation lead from the car.

**malcom2073** · 01-20-2009, 05:33 PM

how transparent are modern large LCD's? I remember taking apart a REALLY old laptop and it was hard to see clearly through it. Though that was old tech and I have no idea how it compares to modern TN panels, but this actually sounds like a really cool idea, and would definently take the unreliability factor out of digital dashes.

**insaneramman** · 01-20-2009, 08:40 PM

Have you looked into a custom sized lcd?

http://www.lcddesigns.com/index.php

I too have thought about this. My idea was a small sub-pc (like the little fit-pc) with an OSD interface networked to the main PC. My main roadblock was lack of funds and programming skill. OH those two pretty much killed the idea FOR ME.

**zapro** · 02-10-2009, 02:10 PM

The LCD panel you need is this: http://www.lcdsolar.com/products/Lcd...il.asp?pnid=17

Then you can program an application on a small embedded computer that controls it all.

// Per.

**mayhembdm666** · 02-21-2010, 03:30 AM

I will say that last product does have a very interesting future for a few projects i have in mind. So might need to keep that one on bookmark for now.