Ok heres the idea. I want a basic LED speedometer(maybe rev's too) HUD display for my car. I want it to be a plug and play thing using the car's OBD port (which supplys power too) But i want to know if its possible to use off the shelf parts to make a small decoder chip and out put it to a Led array? So any idea's diagrams help is much appreciated heres a link the the wiki on OBD which may shed some light on standards and such. http://en.wikipedia.org/wiki/On_Board_Diagnostics EDIT:fixed link
I'm not going be be an expert by any means but.. it would help if your link worked correct one http://en.wikipedia.org/wiki/On_Board_Diagnostics you forgot the 's' then you make/model of car are you obd1 or obd2 etc... from what i can tell they seem to mostly be a serial connection for you'd need to send recuse then read result in a loop to send read though you'll also need the correct code book for you make/model so you know what to send and what was said.. but since we don't know your exact make/model yet and since the voltages/specs shift slightly over OBG-II i don't believe there would be an end all ...
Well OBDII is my car but OBDII has alot of standard outputs so whould work for all post 98 cars i beleive. Tho i do beleive cars are moving to the CAN system (i know even less about that) but i think that maybe ALOT harder to deal with. And srry about the link missed that F up
Ok, not even sure where to start. First off, depending on the protocol your car uses, that will have a big effect (ISO,VFW,PWM). Mine is ISO for instance, the slowest of them all. Only get's 10-15 samples per second which sucks for realtime. Luckily someone just cracked the ECU and now with a cable I can go down to the wire and get 200 a second, plus all kinds of things available now not normally available through OBDII If you just want a speedo and tach, you should be able to do it regardless. Even if it's slow, 5 or so samples per second each for the speedo and tach ain't too bad. You could use interpolation to smooth it out a bit more. If you aren't hooking it to a PC, you could get an ELM chip that's appropriate for you protocol and drive it through a PIC or similar microcontroller easy enough. There are some optic issues to deal with if you want a correctly projected HUD. If you could find a horizontally reversed VFD, that would be a good start. Or even one that supports enough custom characters. Though I don't know how important proper projection (at infinity) is. Yeah, you don't have to refocus your eyes, but on the other hand it seems to be a sticking point. Meaning it's been a sticking point for my own project. Worse comes to worse, having to refocus your eyes on the windshield isn't so bad as you would have to refocus even more to see your normal cluster, so at best, I think it is still slightly better. There is also research that says having the HUD focused out into space can lead to attention tunneling and be a distraction, by not being a distraction A bunch of people (myself included) have been working on a more general HUD project for some time, though we are trying to use VGA screens for displaying video (nightvision) and other stuff. You might find some of it interesting. Here's an old test pic of a monitor on some HUD glass I procured. There is a massive thread here. http://www.mp3car.com/vbulletin/showthread.php?t=73549
I just thought of somthing. It maybe alot easier to read the speed from the instrument cluster since most cars these days use a computer driven system of some sort rather than the old cable driven system. itll be alot less clean, probably less portable to other cars and more difficult to install but should bring the price and complication of the electronics required down considerably.
Good point. The speedo and tach on my car are driven by a 4 pulse per revolution signal, before they cracked my ECU, that's exactly how I was going to get around the speed limitation of OBDII. Read the tach/speedo direct and everything else OBDII There is a thread of mine on this forum on the subject, let me take a look around.
I could always go realllllly DIY and just wire up a camera that and have a vga output of it for the speedometer but that would be fugly as hell and not nearly as clean a concept
Here's two threads on the general question of reading the inputs. http://forums.bit-tech.net/showthread.php?t=73401 http://forums.bit-tech.net/showthread.php?t=107608 If you can get your service manuals for your car, it's a good start. I got mine for about $35 on ebay and they are three massive phone books. I'd imagine yours will tell you how to test your tach/speedo which should tell you most of what you need to know as far as how it works.
The CAN system isn't as bad as prople think, cracking it yourself would probably be a bit of a bitch but theres plenty of people out there selling stuff that hooks up into the CANbus and reads /writes to it, I deal with it every day and haven't really come across many problems that cant be solved by finding where the canbus becomes a normal wiring loom (lights, stereo etc., theres a speed pulse in pin 1 of most modern cars ISO stereo power connector and on the newer style quadlock connectors theres other info available as well (sometimes) )
Yeah CAN looks pretty good, though my car doesn't use it (or not a normal implementation) so I never looked into it too much. Good call on the stereo, I don't think mine has it but I imagine it's common now with factory nav systems available. As a matter of fact, mine is the only 02 Chrysler that can't use the OEM nav because of that. I'm sure you could easily hack it enough, but technically, it's incompatible.
@ shotgunefx, check the back of your speedo, if there's no speedo cable there's a speed pulse, on the main connector to the speedo cluster or on the gearbox are the easiest places to pick it up, ( usually a 3 wire connector on the gearbox) Iso and quadlock = european market cars only excluding most japanese and US manufactureurs
Thanks, got that fairly well covered. I own just about every piece of documentation every made for my car (schematics, service manuals, training videos, tech training guides), looks like Sanford and Son in my house On mine it's a 4 pulse per revolution, there are also several pins on the ECU that supply it as well at various voltages. What's quadlock? I thought a lot of JDM stuff was ISO? My car is a mitsu/chrysler mix and ISO. Though outside of my own model, my knowledge rapidly falls off.
is a quadlock connector (also known as MOST) and Japanese cars in europe rarely have ISO connectors, normally have a specific manufactureurs connection which can be converted to iso with a fly lead mitsi / chyrsler mix..? sounds like an eclipse
I see what you mean about the connector. My car is ISO 9141-2 Pretty close on the eclipse, it's a Sebring Coupe. Basically an enlarged eclipse/galant with a chrysler skin. Built on the same line in Normal Ill. Or rather was, discontinued last year due to the end of the mitsu/chrysler deal.
