Archived

This topic is now archived and is closed to further replies.

Dwiel

Multipule analouge inputs

Recommended Posts

Hey, I am working on the design of software that will go on a computer in my car. I was going to try to feed the computer things like speed/fuel/tach/brightness/air+engine temp, etc. All of these will hopefully be inputed along with controls for varius things like Heating/AC, MP3 Player, Head Lights, etc. How can I best get all of these analoug inputs into my computer very cheaply? BTW. I am also planning connecting an LCD to my only parallel port so I can't use that for anything but it. I would like to keep the cost to around $10 about $20 max. I got inspiration for this thing in this thread in the lounge. Thanks! Dwiel [EDIT] Changed the title to something a little more informative
My home page!!!
Find out about my diy LCD projector and programming projects!
[edited by - Tazzel3d on March 23, 2004 6:36:10 PM]

Share this post


Link to post
Share on other sites
Some ideas thus far...

I think I am going to try to open up a mouse and turn the two axis of the ball into 2 analoug controls. THis can handle things like volume/menu/etc, but not the things that will essentially a voltage that needs to be inputed.

The only way that I have come up with to solve this problem is to get a A/D convertor(s) that can hanlde all of the voltage ranges I will be probing. Then get an oscilator (in the 400hz range) and a 2bit counter. send the counter as 2 of the digital inputs and use a switching mechanism (prolly transistors) to control which voltage goes through A/D convertor and into 8 more of the digital inputs. Only proboblem is that I am not sure that I have 8 digi-ins to work with... I might have to settle with a 6bit A/D or even 4

Any ideas that aren''t so complex? I''d rather stick with the K.I.S.S. ideology.

Dwiel


My home page!!!
Find out about my diy LCD projector and programming projects!

Share this post


Link to post
Share on other sites
Tried looking on ebay for any second hand PCI IO cards, maybe you can get a digital input card with a couple of analogue channels.

Not sure where you are tho Tazz, cos IIRC it is illegal to tamper with the tach in the UK, even if all you are doing is piggybacking off it to get readouts. (Without knowing your car I couldn''t hazard a guess as to how you might pick up the signals.

if you can get small voltage instuments, is it possible to use the serial or paralell ports?, or the USB to supply the power, and pick up the returns on the tx / rx lines.

I''d guess that you can''t do it for less than $10 tho. (If your pc has usb, you could stick a usb to Paralell port adapter on there (in the uk they are about £20.00)

Also, I am not sure how many of those inputs will be analogue. Headlights on / off will be digital. And you may even find that things like tach may be digital pulses on each wheel rotation, not an analogue signal.

Sounds like an interesting project tho, keep us informed how you get on. (PS if you live near an industrial plant, they are often scrapping kit when they recommission / add new plant, and you make (if you can be nice and friendly) get free old kit such as PC cards, DA converters etc (they may be ropey, but at least would prove a Proof of Concept I''d guess.)

Share this post


Link to post
Share on other sites
I have looked on ebay and have found what you are talking about. The only problem is that they were for PCI->Parallel. None had analog inputs . Also, I dont live near many big factories... all of the ones that used to be around here either went to asia or mexico

I was thinking though... might there be a way for me to use the microphone/line-in on the on-board sound? There probobly isn''t anyway to use them unless I want them to be heard on the spkr-out also, which would sound aweful... Also, they would most likely be way to strong and would kill the mobo. Its the only one I have, so I don''t want to mess around.

I am not sure what you were talking about with the tx/rx lines... Were you suggesting using some part of the USB connector? The computer does have 2 USB ports so that is an option.

Also, I live in America where it is also illegal to alter your tach, now that you mention it. But I also dont think that anyone will ever do anything to you if alter it as long as you don''t try to sell it later. I will never sell this thing, except to the junk yard when the repairs for it are worth more than the car So I don''t think that is too big of an issue.

Thanks

My home page!!!
Find out about my diy LCD projector and programming projects!

Share this post


Link to post
Share on other sites
Hey Zach,

I have a very simple solution for you: gameport/joystick input. It is 15pin it has 4 digital and 4 analog inputs. The only consideration is that the analog currents have a 100k resistance. There is lots of documentation available about how to add circuits to computer with this method. E-mail me if you have any questions.

David Collins

Share this post


Link to post
Share on other sites
Is it a newer car? All new cars have the same digital interface under the dash board. For $50 you can buy a kit that lets you check engine codes, as well as monitor speed, tach, temperatures etc...

Modern cars also employ the industry standard CAN bus for communicating information, such as engine tach or speed-pulses, from the sensors to the digital dash board (yes, it's all electronic now, with a small motor making the needle move and appear analog, that's why the things give off a 100W of heat).


If you want cheap, you'll have to buy an embedded uC, such as a Motorola ColdFire. I'm not sure how much the development board is though (it might be a few hundred). With 1M flash and 4MB RAM, they can run uclinux.

.. You could always hack a GameBoy Advance (Arm7 tdmi).

[edited by - Magmai Kai Holmlor on March 26, 2004 11:39:13 PM]

Share this post


Link to post
Share on other sites
Actually, it is a 1991 Pontiac Sunfire. Not too new. Unfortunately.

I will have to look into the gameports. If anything, I can use cooler interface to the next/prev vol up/down, etc. Those are always better as analoug

Its looking like the interface to the speedometer is going to be aweful considering my knoledge of electronics, so I think I am going to settle with interfacing 2 LCDs and some analoug controls for the mp3 player.

Looks like when I get a new car in a dozen years, I''ll have to look back into this

Thanks!

Dwiel

My home page!!!
Find out about my diy LCD projector and programming projects!

Share this post


Link to post
Share on other sites