Remote readout for a scangauge/supermid

[getnpsi]

I came up with an idea, and dont know how to implement it, but i think it would be a good idea for those super mileage geeks. How about running a lead from the scanguage to the rear of the car with a large digital readout for instant/avg mpg for all to see? maybe with a advertisement for this site? If they can be produced cheaply, some sort of donation on purchase to the site?

[dcb]

I've thought about that too (well, not the advertisement bit). FYI, MPG on the rear deck could theoretically be done to a mpguino for about an extra $10 in parts and some fancy finger work.

Basically you would buy a bunch of LEDS and build an oversided LED number display (think black cardboard with a bunch of holes in it and hotglue). Then get an additional atmega168 and program it with your duino board to accept a number over the serial port and display it on the jumbo LED display.



Note: there are enough pins on a duino/atm168 to support up to an 8 digit numeric LED display without extra chips, but you would need 64 transistors to control the segments. So probably worth it to get a MAX 7219 like in the arduino playground example: http://www.arduino.cc/playground/Main/LedControl

[Doofus McFancypants]

Kinda like a MPG-Light Bright!
Cool idea.

I have seen a window unit where you could program different messages to go across the screen - But this would be a lower cost solution.
How would Visiability be? clearly at night would work - might not be enough contract for a "full sun" day.

Steve

[dcb]

I think visibility would be good except for a couple angles where the sun bounces off the back window. You could wrap it in clear plastic and put it on the back of the car too.

Anyway, not that I needed a distraction, but I couldn't help digging into this a bit more I've always thought it would be kind of cool, and definately get peoples attention to see 999MPG popping up on the back of a car while someone is EOCing.

a possible layout:


notes for this layout:
22 controllable segments (MPG is one segment, rest is 4 LED groups)

38 x4 LEDs = 142 LEDs


3 numbers, each enabled by a transistor, scan style

7 segments per number, 7 transistors

transistors for MPG

mouser parts list:
quantity, part
142, 604-WP7113SRD/D 100: $0.06 1.85v 20ma RED LED

30, 610-2N3906 25: $0.08 transistor //not accurate, probablye need a few NPNs too.

1, 556-ATMEGA168-20PU 1: $4.11 atmega168

1, 559-FOX160-20-LF 1: $0.47 crystal

1, 511-L7808CP 1: $0.41 8 volt regulator, 1 amp

4, 512-1N456A 1: $0.06 Diodes (drops 8v to 5v for CPU)

1, 647-UVR1E331MPD1TD 1: $0.12 330UF 25V capacitor

total $16.27 for quantity 1, not including shipping. But a fair bit of soldering and getting a bootloader and program on the chip.

for comparison, the displays a few posts previous go for $400+.

Also note that I've seen regulations about what color lights can be where on a vehicle, so RED is probably the most defendable color for such a display, it is just a fancy taillight then.

[getnpsi]

Well thank you very much for the time researching and checking out the options. It would be neat to have one, but Ill admit i cant make this myself. I would have to take a week vacation to teach myself how to make a reliable board, and I dont see it happening.

[dcb]

No prob, I think it's kinda fun sorting this stuff out. Course it is a lot easier to think about it than to actually do it

FYI, here is what the numbers part of the schematic *might* look like, I have no idea if it actually works. Basically you enable the numbers one at a time and turn on the corresponding segments for that digit only while it is enabled. Go through the digits fast enough and it looks like they are always on. An additional capacitor per segment/digit might help if there are brightness issues.

[dcb]

Well, I had to get a special part for my oscilloscope from mouser so I ordered a pile of LEDs while I was there (and more mpguino fixins), we'll see what happens

[bbjsw10]

<----Subscribes, gotta see this.