I will not do this project. I will not do this project. I will not do this
project. I will not do this project.

Well, at least not this week. :-)

Better watch that. First, you have a random thought. Then you get
interested enough to look into it a bit. Next thing you know, it's an
obsession and you're spending all your free time making it happen.

Don't ask me how I know this. ;-)

"Paul" wrote in message ogers.com...
I've been wondering, what would be involved in having a computer interpret
and display gauge readings.

By this I mean something such as having a laptop receiving inputs from the
various gauge sending units such as oil pressure, engine temp etc. and then
displaying them in some way.

I don't believe this is something I would actually do, it's just I was on a
long drive yesterday and it got into my head and I would really like to
figure it out.

I've googled unsuccessfully (I'm ashamed to admit) so if anyone can point me
in a direction ...

This depends a lot on the engine you have. Some modern engines have a
digital interface for getting this kind of data. All new cars have
this kind of featu http://www.obdii.com/

For odb-II you can built or buy a very cheap interface for a serial
port and even find some programs for displaing the data.

I thinh most EFI-engines will a have similar interface, but porbably
they will use proprietary protocol, which might be hard to figure out.

If yours does not have any of these, you have two approaches:

1. Use the sensors the engine all ready have.

2. Install your own sensors.


In the first approach the problem is to find out the measuring
principle of each sensor. Also the typical sensors used are quite
inaccurate. You probably need an A/D converter, which can be bought as
an card to your computer (expensive), as a separate chip (5 $) or as
integral part of a microcontroller (AVR, PIC etc 5-20 $). The accuracy
you can get is probably ~10%.

In the second approach you can choose better and more easily
interfaced sensors. You can find cheap digitally interfaced sensors
for pressure, temperature etc., which can be directly connected to
parrallel or serial port, but I would recommed using a
microcontroller, which can collect all the data and even store it and
then send it to your PC via serial line. With this approach you can
get accuracy of 0,1-1%, depending on the sensors you choose.

I have built a weather station and an altmeter using Atmet AVR
AT90S8535 processors (www.atmel.com). The barometric pressure is 1
mbar (0,1%) accurate and temperatures are displayd with 0,01 C
resolution (0,2 C accuracy). All the data (including wind speed and
direction) is stored to non-volatile memory every 10 minutes for a
month. I can then read the data to PC once a month. All data (also
logged) can be viewed from an LCD-display or sent online to PC. The
cost of the equipment withou wind sensors was less than 50 $, but took
a lot of free time.

Next project I'm planing is an battery monitor, which displays the
voltage of the batteries as well as the current from each battery.
Current would be measured from the voltage drop of earth cables (max
+- 0,1 V) with a 24-bit A/D converter. Current could be then measured
fom a few mA to 200 A in both directions with accuracy of ~1% of the
reading. After this it would be easy to calculate how many Ah is
put/taken from/to each battery. This system will cost ~30 $.

Joakim

"Paul" wrote in message ogers.com...
I've been wondering, what would be involved in having a computer interpret
and display gauge readings.

By this I mean something such as having a laptop receiving inputs from the
various gauge sending units such as oil pressure, engine temp etc. and then
displaying them in some way.

I don't believe this is something I would actually do, it's just I was on a
long drive yesterday and it got into my head and I would really like to
figure it out.

I've googled unsuccessfully (I'm ashamed to admit) so if anyone can point me
in a direction ...

This depends a lot on the engine you have. Some modern engines have a
digital interface for getting this kind of data. All new cars have
this kind of featu http://www.obdii.com/

For odb-II you can built or buy a very cheap interface for a serial
port and even find some programs for displaing the data.

I thinh most EFI-engines will a have similar interface, but porbably
they will use proprietary protocol, which might be hard to figure out.

If yours does not have any of these, you have two approaches:

1. Use the sensors the engine all ready have.

2. Install your own sensors.


In the first approach the problem is to find out the measuring
principle of each sensor. Also the typical sensors used are quite
inaccurate. You probably need an A/D converter, which can be bought as
an card to your computer (expensive), as a separate chip (5 $) or as
integral part of a microcontroller (AVR, PIC etc 5-20 $). The accuracy
you can get is probably ~10%.

In the second approach you can choose better and more easily
interfaced sensors. You can find cheap digitally interfaced sensors
for pressure, temperature etc., which can be directly connected to
parrallel or serial port, but I would recommed using a
microcontroller, which can collect all the data and even store it and
then send it to your PC via serial line. With this approach you can
get accuracy of 0,1-1%, depending on the sensors you choose.

I have built a weather station and an altmeter using Atmet AVR
AT90S8535 processors (www.atmel.com). The barometric pressure is 1
mbar (0,1%) accurate and temperatures are displayd with 0,01 C
resolution (0,2 C accuracy). All the data (including wind speed and
direction) is stored to non-volatile memory every 10 minutes for a
month. I can then read the data to PC once a month. All data (also
logged) can be viewed from an LCD-display or sent online to PC. The
cost of the equipment withou wind sensors was less than 50 $, but took
a lot of free time.

Next project I'm planing is an battery monitor, which displays the
voltage of the batteries as well as the current from each battery.
Current would be measured from the voltage drop of earth cables (max
+- 0,1 V) with a 24-bit A/D converter. Current could be then measured
fom a few mA to 200 A in both directions with accuracy of ~1% of the
reading. After this it would be easy to calculate how many Ah is
put/taken from/to each battery. This system will cost ~30 $.

Joakim