[Fred Kaluza]

Has anyone been able to extract segment driver information from the dash MPG display and been able to fabricate a nice bright large display for MPG so drivers behind me can see how I'm doing? Are their any remote MPG display kits being marketed? I think that alone would be responsible for for increase in Insight interest as much as anything else. Fred in Michigan.

 

[Holicow]

This was brought up recently, but I can't find the thread. There are no kits available, that I know of. I would love to have one.

It seems we are at the mercy of someone who knows more about car electricals than I.

 

[james]

I haven't done it, but from the wiring diagrams in the manual, it looks as though all the info that's displayed on the dash is being sent over a pair of wires, using some sort of serial protocol. So if you had access to a recording scope or something of that sort, it should be pretty easy to decode. Then if you tap in to those lines, you could use them to drive any sort of display.

 

[Resist]

I have already seen LED moving message sign type of plate frames on cars. I can't find information about them though. Now if only someont could tie that into the instant mpg indicator.

 

[ext1jdh]

I know the plate frames use standard 9 pin serial that you plug into a PC. It should be pretty simple to throw it together but I have neither the time nor the inclination to tear my dash apart

 

[Guest]

It should be pretty simple to throw it together but I have neither the time nor the inclination to tear my dash apart

It is more complicated than it seems on the surface. First you have to reverse engineer the protocol used to send the information to the dash display and extract only the information desired. Then you have to encapsulate that data in a different protocol (RS 232 serial?) and send it to the second display. The savvy electrical engineer could probably build a PIC microcontroller circuit to do the decode/encode, but deciphering the signal in the first place is no small task. Anybody have a recording O-scope handy?

 

[Fred Kaluza]

Well, OK, I don't have a scope that records anything and I also don't feel like tearing the dash apart.....yet. But, if we decode the data stream, then we still need to create a "smart" rear display. One that has enough brains in it to decode and display just the same as the one in the dash. I'm proposing a "dumb" display. I'm not sure how may segments are in the dash mounted unit or of the segents present, just how many are being used. But, assuming it's seven per digit, then maybe a ribbon cable with 3x7 plus hot & ground equals 23 leads running from front to rear. It's probably simpler to splice into the driver outputs anyway. I admit using one of those pre-made scrolling displays would be really cool since theoretically you could send other text. Still thinking here. Thanks for the ideas. Fred in Warren, MI.

 

[Yves M.]

I agree with Fred. It must be simpler to connect to the display itself. And then those leads could be used through transistors, to power up a bigger display.

 

[james]

I don't think you'd have to tear the dash apart. Everything comes out of the same processing unit, which if I remember correctly is mounted under the dash on the passenger side, and fairly accessable. Should be the same one that the diagnostic connector goes to.

Getting to the display is (according to the shop manual - I haven't actually done it) a major PITA. Pull the airbag, drop the steering column...

 

[Armin]

not that easy

assuming it's seven per digit, then maybe a ribbon cable with 3x7 plus hot & ground equals 23 leads running from front to rear. It's probably simpler to splice into the driver outputs anyway.

Fred,

I don't think it will be that easy! The dash display is LCD, and judging by the total number of segments, it must be highly multiplexed.

First, it will be very difficult to tap any of the signals, since the wire capacity or the load of any circuit you hook up to them will dampen the original signal and screw up your dash display. LCD drivers are not made to really "drive" any load.

Secondly, even if you use some low capacity, high impedance buffers to recover the signals without harm, you now need to demux the LCD drive signals to figure out which segments are lit. It's doable, but by this time it's probably easier to reverse-engineer the communication protocol.

 

[Mike Dabrowski 2000]

I have been thinking about this since I got my Insight in 2001. Reverse engineering the serial communication protocal could be very time consuming, and tapping into the LCD display which is probably multiplexed would be messy. I figure that The simplest way is to have a bright rear color video display, and a small color video camera that is focused on the part of the main LCD that you want to display. It would probably not be daylight readable, but would be easy to see at night.
Mike

 

[Yves M.]

Hello Mike,

What do you think about a tranparent window over the display that would reflect to a small box. In that small box, their would be light receivers for each segment where the segment reflect. Those would power up transistors to then control any size/strength of display

 

[Mike Dabrowski 2000]

Hi Yves
As you may remember, I had made a reader for the bar graph that captured the average intensity of all the bars, and converted it to an analog voltage. This voltage was to be converted to a repeater bargraph in the rear window.
It could be made to work well(+- 1-2 bars) as long as the ambient light was dim, but if the sun got onto the display it would cause the voltage to change wildly, so I gave up on that approach, and figured that someday I would have the time to reverse engineer the "meter serial" communication and keep it digital. I also had a heads up lean burn led that used a single fiber optic with detector to read one LCD bar at about 65MPG.
It had the same problems with ambient light.
If one is willing to completely cover the bargraph so ambient light cannot get into the detection circuits, you could put the photo detectors right against the LCD bargraph. Once the repeater circuit was working, an additional bargraph could be mounted over the opaque cover so the instant MPG bargraph (repeater) would still show the MPG on the dash, and also in the rear window. It may be worth a try?
Mike

 

[ilusnforc]

It just might be easier to build a simple circuit using 2 large 7 segment displays and a number of switches to set the numbers you want, then you can just put your average mpg on it every so often... and also next to the 2 7-segment displays in your back window you can put a sticker that says "mpg" instead of making the letters out of LED's or something, the sticker would just be much simpler. I just might be tempted to do it. I'll have to have a talk with one of my electronics instructors...

 

[bfivelover]

How about this: http://www.youcansave.com/billboard.asp

 

[ilusnforc]

nice... that does look like a pretty interesting idea... I've already started collecting components to build the circuit... hopefully it works out! I'll post more once completed if it works like I wanted it to.

 

[Mike Dabrowski 2000]

While a rear display of MPG that is hand entered would be fairley easy to do, it will not have the real time effect that I was hoping for. I mounted a color ccd video camera on a simple metal bracket that is pressed down into the crack between the steering column cover and the dashboard. The camera is kind of big, and blocks my view of the mpg bargraph, but is a good proof of concept. I made a close up lens so the camera can be focused on just the MPG and bargraph. The bargraph is visable with 0 to 75 MPG. The display is a bright 5 inch LCD video monitor. The display is clear and quite readable once it begins to get dark.
I have ordered a tiny 1.4X1.4 inch color camera that should be able to be mounted out of the way so the instrument panel will not be occluded.
I will post some photos once I get it finished.
Mike

 

[Holicow]

I'm impressed!!

Can't wait to see the evidence. One question: are you saying it only shows part of the instantaneous bar? If so, is it because of the angle? Will the new camera have a wider angle?

I guess that was 3 questions. No charge for the other two...

 

[Mike Dabrowski 2000]

The full bargaph can be displayed but I wanted to have the MPG diaplay as large as possible. Moving the camera back a little includes more of the bargraph.
The camera has a pan and tilt mount so anything part of the display can be repeated in the rear display.
I have not found a reasonably priced transflective LCD video display. That type would show an image even in the day time.
Mike

 

[Mike Dabrowski 2000]

I got the color video cameras today. I got the 1.4" square one that I had refered to, and an even smaller 5/8" square one. Both have adjustable focus lenses, and can focus to within a fraction of an inch of the lens. I like the 5/8" square one, since it is so small that it can sit slightly to the left of the MPG display, and not block anything, while capturing the full digital MPG display, and most of the MPG bargraph.The resolution is pretty good, and if the image does not include a lot of dark background, it is able to adjust the exposure to give a nice capture of the bargraph and digital display.
Both cameras run on 9-12VDC, so I needed to put an LM7812 linear voltage regulator in the power line, since the unregulated 14 + volts out of the lighter jack would damage the cameras.
Now I need to come up with a mounting system that will hold the tiny camera where I want it for the best capture.
I got the amazing little 5/8 color camera from:
http://www.starkelectronic.com/elycctv.htm
for only $49.95, in case any one else wants to try this.
I will mount my LCD display into a recessed custom mounting box in the bottom of my Insight's rear deck window, so it may be daylight viewable, and will post some photos when it is done.
Mike