Heres the deal: I want to take the wires from misc. parts of the car, e.g. Oil pressure, Air/Fuel, Fuel pressure, voltage, Tachometer, Fuel tank, ETC....
And hook them up to a computer somhow, for display on a laptop, which i would hook to a LCD Screen, and have a nifty display of all the stuff i would normally need guages for.

I can make my own program, but how would i get the DATA into the computer? Do all guages use a VOLTAGE or RESISTANCE for readouts? If so, could i use say, a parrallel port and wire each sensor to a pin on the paralel port of the computer and use a program to detect the volts or resistances? AM i going about it all wrong? Basically, i want my computer to be a ECM and just read out the info to me on the screen.... BTW my car is NOT computer controlled, nor does it have a computer in it.

 

I would hate to take the "If you are asking this you can't do this" approach but its probably the closest to right. A laptop is an expensive and unreliable piece to use as an interface. You would be better off using a small microcontroller. But I know the next thing you are going to say is that you can easily write a C++ program for the laptop where the microcontroller is unknown territory for you. So to move on, other than the tach the gauges work on resistance. As a sensor's reading changes its resistance changes. Gauges normally work off of current which changes in relation to the resistance. What you need to do is set up a resistor between +5V and the sensor. Then measure the voltage at the sensor with an analog to digital converter. 8 bit accuracy should be sufficient. You will want a multichannel converter so that you can use one converter to read several sensors. Since the data is all low speed it is not important to be able to sample each sensor at exactly the same time. Otherwise you would need an ADC for each sensor making life harder. You will want to build an interface to the ADC, probably using the printer port. For the tach probably the easiest way for you to deal with it is to buy a frequency to voltage converter IC. With a little filtering of the tach signal this IC will perform reasonably well at converting RPM to voltage. It is what analog tachs usually use anyways. Check around because I know at least one data sheet for a frequency to voltage converter chip contained a schematic for a tach. I just wish I could remember which chip it was. Once you have done this you can sample the tach just like another sensor input. Then you will want to add to your parallel port interface a bidirectional port to communicate with an LCD display. This is hardly enough information but it outlines a possible solution using the equipment you are considering. You will need more information on ADC's, frequency to voltage IC's, the exact resistances of the sensors and how they change, and how a printer port works. The internet should be able to tell you most of this. The sensors will probably have to be played with to find their general values. Leave yourself calibration variables in the program to adjust the calibration afterwards.

This does offer the advantage of growth from more than a gauge system. It is possible to roughly calculate horsepower from the tach versus time. It is also possible to record all of the engine stats during a run to analyze them for improvements. If you wanted to go wild you could even mount ABS type sensors on the front and rear wheels to determine the amount of tire slip. With measuring the front wheels you should be able to calculate 1/4 mile times pretty accurately.

 

iiiinteresting.... printer ports no problem, but i suppose the rest is... I've never used a digital analog converter or whatchamacallit or fluxcapacitor thingy.... hmmmmffff.... Just looking for a decent way to bypass the whole guage thing. If 1/4 times and RWslippage comes out of the deal, then hell yeah sounds like a plan, but, like you said in the begining, Ive no clue where to start.

Anyone have any ideas forthcoming with this, such as ways to interact with the data, or how to accuratly measure it out using the whatchamacallits described, it probably sounds harder than it is, after all, parallel ports are fairly simple things
I will do some research...

 

the 8 bit ADC chips are like $5.00 a piece. where to go from there? LOL i have no clue. I emailed a guy who uses them all the time for stuff, mayb he will haves um answers. i really want an On-board 1/4 measurer and an on-board multiple readout guage thingy. i will persue with much interest!!!!!! Any help is of course welcome, especially when it comes to putting it all together. if it does really well, i will consider posting how i did it and what you need etc... Plus the code i used, so anyone could do it.

 

I am nearly 90% sure of how i am going to do this. I just purchased a data acquisition tool that will plug into my serial port of my laptop, and i will use that and a software program i make to access the data points in whatever i connect. blah blah blah it should be really cheap to do too... the aquisition tool is only $13.00!! and it comes with cool active X controllers for acquiring the data too!

this is nuts, why hasnt anyone thought of it before?
Oh yeaah... I guess thats what ECM's are. just without the cool laptop display

 

People do think of things like this. It takes more than coming up with the idea to make a product. You got a good deal at $13, I just hope it has multiple channels. You will still have to mess with converting the tach signal. This does sound like a good start for you. The work isn't over yet.

I'll add that one thing you are going to encounter is that LCD displays suck when it comes to visibility. Gauges usually have to be read at a glance. In most cases you will not be able to do that with an LCD display, even if you make a picture of a gauge. This has been a rap against digital gauges for as long as they have existed. This is true even with displays using LED's which are brighter and easier to see. Numeric displays are useless in a race, and LED versions of an analog gauge are inaccurate and still not as easy to read. So for accurate gauges that can be read at a glance or carefully inspected people stick to quality analog gauges. If this is what floats your boat then have fun. The only real advantage is in the collection and analysis of the data.

 

It has 4 channels, of which im probably going to use them for one sole purpose I.E. monitoring all the things associated with a good boost motor like fuel pressure, air/fuel, boost, etc...
Or maybe nitrous related things...

But like you said, I can collect and store data from an Entire Run, and look back at it and see where maybe i leaned out for a second, or where my engine stopped making reasonable power and MPH/RPMS kinda sat still, or whatever.
Getting the air/fuel guage will be the easiest in the world, i check the O2 sensor sending unit, it sends .05 volts in .05 incriments up to 1.0 volts to tell rich/lean, so that will be a direct hookup
As the problems arise Ill check each one out, and as for display, i might just use the laptop itself, who knows. When i get the data aqcuireing thingy Ill check out all my limitations.
-----It uses VOLTAGE to input readings to the computer. i can measure from +-10 volts.
out of curiosity, know where i could get a good DC Amplifier with a Gain factor of 10? It would make readings much easier....
Since it uses voltage, then things that dont use voltage, like boost guages which actually use PSI, how in the hell would i hook that up to voltage? impossible? somthing that increases volts as PSI goes up? weird...
And on the same note, besides voltage and PSI what other measurements do guages use?

 

You can add to these channels using a 4066 IC. It is a basic analog multiplexer. But it would have to be controlled by a digital line to switch the inputs. It basically acts like an input switch. Probably more than you want to get in to right now since you have bypassed some of the hardware.

I don't know of any canned amplifiers but you can build a simple amplifier yourself. Basically all you would need is a 741 op-amp and two resistors. You can look it up on the internet or Radio Shack carries a series of tiny books called the engineer's mini-notebook. One I know is based on op-amps. It has sample circuits and basic information. From this you can build a circuit to amplify your signal by any amount you like.

For PSI you need a pressure sensor. Like the other sensors it is probably going to vary resistance with pressure. The sensor needs to operate in the range you want. Then with a resistor to +5V, or I guess +12V would now be acceptable since you can measure +/-10V, you could make a voltage output. Maybe some cars have a factory boost sensor that will work for you. I don't know of any off hand but maybe other people do.

 

whats a 4066 IC ??? lol im still dumb, i just learn fast. dont use analogies in your writing hehehe

 

I am working on the same thing now just have to wait for the firebird to come i sold the camaro this week =/ you could work on testing your stuff out of the car with a variable resister 1st and go from there thats what i have set up

https://www.thirdgen.org/techbb2/sho...threadid=77961

https://www.thirdgen.org/techbb2/sho...threadid=75604