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Remote "Back Window" MPG Display?

13676 Views 75 Replies 29 Participants Last post by  Insightful Trekker
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.
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Thanks guys
I took a ride last night after making some of the changes that were suggested. The major one was to focus on getting the best display of the digital information . What that display looks like is shown @ ... isplay.htm

It was raining last night so I took some towels and propped up the rear display in the little window on the passenger side.(I was in a hurry, so I was the passer.)
That way it is only visible when the passing car is only 5-10 feet away when iit is easily readable, and he is likely to look,
That also allows the display to be inside out of the weather.
As Calpod suggest, a single display just behind the seat backs would be readable from either side, or could be mounted on a base that you could toggle between passer or passee positions. while driving. It could also have a parking lot position looking up out of the window for people walking.
Just a thought:
Maybe only show the MPG value e.g. "62.5"
in the LCD.
And in order to hide the lower section and to show that the value is MPG, I would add a sticker under the value, to read "MPG".

So it becomes:
| 62.5 |
| MPG |
This way the value is as big as possible and it will not show the partial 0 to 50 MPG display.
Hi Yves
I moved the camera in closer as you suggested, to see if their were any issues.
The camera is easily focusable to only include the numbers, but to get all of the potential digits including the 1 for over 100MPG, the numbers for the bargraph can still be seen. A simple black tape mask can solve that problem. The digits were about 1.75 inches tall on my 6.8" LCD. Eliminate the 100's digit, and the digits can be over 2" tall.
One problem that cropped up was that the #12 wire that holds the camera, was not stiff enough to hold the camera perfectly still when navigating bumpy roads. The shake that was not a factor at lower magnifications became quite noticable at the higher magnification. The camera was close enough to the display, to be slightly in the field of view, whereas it was not blocking anything important when it was in the partial bargraph view. Both of the issues could be easily fixed with a little playing around with the mounting wire, and the angle of the camera.
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I have had my rear window display installed and functioning for about 3 weeks now with large highly visibly (best early in the morning or late afternoon and very bright at night) 3" tall digits. It worked very well and I got quite a bit of attention from it.

Unfortunately it does have its drawbacks. The numbers do not change automatically, I wanted to use 8 switches to make 2 4-binary-digit BCD to 7-segment decoders but they run at digital 5V levels, and the large 3" digit 7-segment displays I found do not turn on until around 11V. So, i just wire the segments i want turned on directly to ground and i connect the anodes of the displays directly to a 12V source that turns on with the ignition. It does the job.... however, recently i noticed two of the segments on the left display are no longer working.... they must have burned out. I would think they should last a lot longer than that, but I suppose being exposed to sunlight and constantly turning on and off and being turned on for long periods of time (30mins to an hour) several times just started burning segments out... for now i have just rearranged the displays so they could be useable, but i am limited to the numbers i am capable of displaying. I hope there is some type of warranty on these... only one display has been affected so far. they cost about $10 each plus shipping, plus I paid $5 for the vinyl lettering, so all came out around $30 for the wire, circuit board, displays... any comments or suggestions??
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Ilusnforc - It looks Way cool ! :eek: I'm really interested. Let's see if I understand what you have/have not done:
1. The display does NOT automatically change - you have to set it to whatever you want? How ? A Key pad? While you drive ?
2. Circuitry - Could this be mass ( 100 units?) produced ? How much ? I might be willing to "upfront" the capital $'s depending on a few things. More on that later
3. Install - What would it take besides 12V as you pointed out.Where is this 'Gizmo' mounted? Size ?

Lets explore this a bit futher depending on your answers....
Looks great. That should get some people interested in the car as you drive around. Whenever it is cold and rainy and I see a motorcycle driver who looks miserable I always wonder what he would think if he knew that I was getting better mileage. Have fun, RIck
Hey Mitch...
I also thought about mass production but only if I could make it look and function like a professionally built product. I talked with my local honda dealer who gave me a number for American Honda Customer Care or something, from there I was given an address and had plans to mail them my ideas to see if they could help me to tap into the computer to decode the signal required to automatically set the gas mileage numbers on the display, then i would just have to make an easy install kit, and make sure the product is durable and built to last, like i said 2 of my segments on one display already seem to have burned out.

1. Correct, the display does not automatically change. The numbers are manually set. This is called a common anode 7-segment display. You connect +12V to the segments you want to light up, then you ground the anode for the entire display. If you want a different number, you have to disconnect the wires for the segments you dont want lit up, and connect the ones you do want to light up.

2. Circuitry.... could easily be mass produced, but like I say, the quality is not exactly what the people would want at this point.. unless they dont care about the way it looks from inside the car or the durability as far as how long it could last. other than that, it does look good from outside behind the car, and i have had many compliments both on the road and even stopped, thumbs up all the time... way more attention then I used to get without it.

3. Install... was relatively simple... find +12V source that turns on with the ignition, and a good ground, and it virtually snaps into the back window because its such a perfect fit...

I'll get more pictures from the inside when its daylight... and if anyone is interested then i'd be glad to make more like mine... just to let you know it is manually set and i cannot guarantee how long it will last. estimated cost appx $40 +shipping (I would not be making any money on it at that price).
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Hrmm, if you used light emitting diodes for the display you wouldn't have the problem with burning out. Of course, that would be somewhat time consuming to produce, but it would be effectively permanent. If that was a no-go using liquid crystals to block certain segments would allow you to use a single light to illuminate the whole thing which would reduce both the number of lights needed and the frequency that the light would need to be changed. (Because the lights would not be going on and off frequently, which is fairly stressful for incandescent bulbs.)
Looks real nice. Most of the 7 segment displays that I have ran into are not designed to connect directly to the power supply, and need to have current limiting resistors for the segments. This may be why you are loosing digits. The specifications for the displays should tell you how many volts and MA each segment can use, and an appropriate series resistor should be in each segments circuit.
You may want to look into getting an LED digital volt meter instead of the 7 segment displays, so that you can just dial in a voltage with a pot to make the display read what you want?
Chips are also available that will drive your 7 segment displays while converting a decimal number to the 7 segment control signals. It can be done with diodes as well. If you would like some help with the circuits, let me know off list.
I have built a video distribution amplifier with gain control for my video based MPG display, It has the ability to drive 4 video monitors from the single camera.It also lets me turn the 4 outputs on or off individually.The gain control will let me improve the display contrast.All that is left to do is for me to build two LCD monitor enclosures that fit into the two small triangular side windows. I hope to get to it this week.
Have fun.
Mike :lol:
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LCD = liquid crystal display

LED = light emitting diode
Ok guys, I'll be honest with you ..... I don't know a diode from a LED or an LCD :oops: I may have current limiting resistors in my brain! But I do think that this type of thing would be great and numerous Hybrid owners would use it. Like you pointed out Ilusnforc, the 'attention' factor has hit the ceiling. I'd like to have a nickle for every time someone has asked me " How do you like your Hybrid - whats your MPG "
I was really hopeing that the display would change with at least a keypad, I'm sure the fail rate your seeing will be worked out - and I don't believe Honda will give you much info -they wanna sell cars, not modify them.
Mike's idea also has great potential, but in order to go ahead with either, I think the areas of cost, ease of install and life span need to have the bugs worked out..
I'm gonna pay close attention to this thread - I'd Luv to have something like this ! :)
Fred Kaluza said:
to fabricate a nice bright large display for MPG so drivers behind me can see how I'm doing?
I thought about doing this, but decided to print two bumper stickers & attach them to my rear window instead:

80 MPG!

That draws enough attention, and gets the point across.
The reason I wanted to contact Honda is for promotional purposes. If Honda could help me to engineer something way cooler, then it would be of more interest to Insight owners, therefore more would be installed, and more people would see the Insights with displays and have more interest in them and would be more likely to buy one. So, the purpose was to be able to see more Hybrids on the streets.

maybe i'll try ordering more displays, and try using some current limiting resistors... we'll see what happens. If anyone is interested, I would be glad to make another one.
probably already been suggested

But just incase, I don't guess any of the mpg info can be read from the obd II port? Could it be derived the same as the on board computer is dueing using fuel port volumes and just integrating with uhmm mileage. If thats uhmm readable?
If you can figure out a way to tap into the computer, be my guest!
Also, if you can find a way to measure things like your speed, amount of fuel being used, distance traveled, then be able to calculate MPG then please let me know, and I'd be glad to do it...
Not as easy as it seems at first.... I'm just trying to keep it simple.
good suggestion though, Thanks!
It would be great if we could come up with a display that connects into the OBD plug under the dash, like the car chip does.
Using OBD data

Here's a palm-pilot OBD scanner that can display real-time MPG.

Then you can buy an interface to a VGA display, such as this one:
The display interfaces to the memory slot, not the regular interface, so you can simultaneously interface both the OBD scanner and a display.

I just thought of this today. The rear display should also show what your local gasoline costs. Something like: "60mpg @ $2.50/gal". With the price of the gas being a number you have to dial in and the mpg showing real time mileage.

Oh that would really piss off those big SUV drivers. :)
I would use a phototransistor

I have an idea. I don't own an insight so I can only go off of pictures and many dealership test drives, so this might not be possible.
I would use a phototransistor. I would put one phototransistor on each segment of the 7 segment displays for each number in the dash. I would then have the phototransistor feed another 7 segment display in the rear of the car. If you can't get a large enough phototransistor to power the rear display us a relay or a large transistor. I would have the emitter lead on each phototransistor feed the rear display. Whenever the phototransistor had light (from the 7 seg display on the dash) is would have voltage on the emitter lead. You might have to use an opaque glue of some sorts to prevent ambient light from getting to the phototransistor. Of course do not put this glue on the phototransistor's eye because it would not be able to see any of the light from the led.
I have been thinking about this project and although I don't know much about electronics, here is an LED 7 segment display that is about 3" tall and cheap. Maybe a digi switch to make it work?? That's about as much electronics as I know.

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