Digital dashboard?

T

Tim Fish

Guest
I'm building a kit car and I want to build a digital dashboard for it. I
have no problem with the rev counter (tacho) as I will just use a freq. to
voltage converter and feed that into a bar graph display driver.

The problem I have is when I come to the digital speed and other digital
displays like water temperature and oil pressure.

for speed I have a frequency coming in from a sensor
oil pressure, water temp and fuel I have resistances from the sensors.

Has anybody got any good ideas for converting these input signals into
numerical outputs?

my first thought is AD converter then convert this in a display driver
(LED).

But then I cant be too sure how these will be calibrated and things?

Thanks,
Tim
 
Tim,
I think your first thoughts are correct. Obviously, if you want a digital
readout on your displays then some form of A/D is required. If you are
reading a resistance then a current source of some sort would be useful in
order that you can get a voltage across the transducer to feed an A/D.
Sampling frequency is not much of an issue here because the variables all
vary very slowly (relative to other common A/D applications), so I guess it
comes down to choosing an A/D with sufficient resolution and accuracy. I
would suggest getting something with a built in voltage reference and a long
integration time to smooth out any noise - remember the equipment will be
operating in a pretty hostile environment. The dual slope type used to be
favourite because of the inherent minimisation of errors - not sure if this
is up to date info anymore.

One other consideration (among many) is the transfer characteristic of the
transducers. i.e. are they linear ? or will you require some form of law
bending system to get the required readings. Transducers are quite often
non-linear so doing your homework here is essential.

Good luck!
--
Dave Wooff
dave@dmwooff.freeserve.co.uk
Tim Fish <timfishy@orange.net> wrote in message
news:bjamc.428$NK4.15358@stones.force9.net...
I'm building a kit car and I want to build a digital dashboard for it. I
have no problem with the rev counter (tacho) as I will just use a freq. to
voltage converter and feed that into a bar graph display driver.

The problem I have is when I come to the digital speed and other digital
displays like water temperature and oil pressure.

for speed I have a frequency coming in from a sensor
oil pressure, water temp and fuel I have resistances from the sensors.

Has anybody got any good ideas for converting these input signals into
numerical outputs?

my first thought is AD converter then convert this in a display driver
(LED).

But then I cant be too sure how these will be calibrated and things?

Thanks,
Tim
Click to expand...
 
Hi Tim,

Just to throw out an idea: How about a nice panel PC that has plenty of AD
channels and a large color display? Then you'd have a dashboard like those on
the newer generation business jets. Of course, on the planes the usually don't
run them on Windows...

You'd have to be versed in programming, or know somebody who is. But now you
could have custom displays, for example RPM with yellow and red ranges where
these ranges move with cylinder head temperature, oil temp and so on. If
money isn't an objective you could install a 2nd one that displays the GPS
maps. I'd bet that would be an eye popper.

Just watch out that it's all safe and legal.

Regards, Joerg
http://www.analogconsultants.com
 
This was a first idea that i had but iwasnt sure really. I could also have
mp3's on it too...

I think a new ferrari has this and all the people doing reviws for it say it
is really bad because you cant read it in sunlight. i suppose you could be
really clever and have an auto-adjusting backlight...

My first option was to get some dials until i found out the price... For a
full set of dials (speedo, tacho, oil pressure, fuel level and water temp)
it was going to cost over Ł250 for the dials that i liked so i though for
the time it would take for me to earn this sort of money (student ish) i
could make something that was much more interesting.

I have been thinking and have almost decided that i would have engine RMP on
an old analoge dial so i can see a nice rate of change and change gear at
the right time. I could then have all the other dials on a small TFT etc.

I have basic programming knowledge (visual basic, HTML, Java, etc) most of
which is self tought.

Does anybody know of andbody that has done this and if so have they
documented it? I really wouldnt know where to start. ADC's to pc, read
inputs calcutate using formulas, output somehow onto VDU. Then warnings
could be added if threshold are triggered... maybe this could be a firmware
update :)

I dont know about the legality though...

many thanks,
Tim



Joerg <notthisjoergsch@removethispacbell.net> wrote in message
news:4099597D.DFF6C3E1@removethispacbell.net...
Hi Tim,

Just to throw out an idea: How about a nice panel PC that has plenty of AD
channels and a large color display? Then you'd have a dashboard like those
on
the newer generation business jets. Of course, on the planes the usually
don't
run them on Windows...

You'd have to be versed in programming, or know somebody who is. But now
you
could have custom displays, for example RPM with yellow and red ranges
where
these ranges move with cylinder head temperature, oil temp and so on. If
money isn't an objective you could install a 2nd one that displays the GPS
maps. I'd bet that would be an eye popper.

Just watch out that it's all safe and legal.

Regards, Joerg
http://www.analogconsultants.com
Click to expand...
 
"Tim Fish" <timfishy@orange.net> wrote in message
news:bjamc.428$NK4.15358@stones.force9.net...
I'm building a kit car and I want to build a digital dashboard for it. I
have no problem with the rev counter (tacho) as I will just use a freq. to
voltage converter and feed that into a bar graph display driver.

The problem I have is when I come to the digital speed and other digital
displays like water temperature and oil pressure.

for speed I have a frequency coming in from a sensor
oil pressure, water temp and fuel I have resistances from the sensors.

Has anybody got any good ideas for converting these input signals into
numerical outputs?

my first thought is AD converter then convert this in a display driver
(LED).

But then I cant be too sure how these will be calibrated and things?

Thanks,
Tim

Some years ago, I was building something very simular. I made a display
Click to expand...
panel that mounted in front of the original dash display, leaving the
odometor etc. for legal reasons. I was just adding my sensors to feed the
electronics. I had tach in the form of 2 lm3915 bar/dot displays, 3 - 1
inch led display for the speed, 6 - .25 inch displays for the odometor.
Several bar/dot's for ( temp/ batt volt / oil / fuel ) .
The legal worries you may have is only in the odometor, as it is illegal to
tamper with it.
Good luck n have fun..
 
The legal worries you may have is only in the odometor, as it is illegal
to
tamper with it.
Click to expand...
Oh hell. My kit car is based on an old Triumph. I am installing a new engine
and I have chucked the old dials because they were full of water. I think I
have a note of the mileage. Oh well I'll have to sort something out.

Tim
 
In message <nmvmc.704$NK4.49202@stones.force9.net>, Tim Fish
<timfishy@orange.net> writes

Sorry my newsreader has already expired this item, so I can't attribute
the first quote.
The legal worries you may have is only in the odometor, as it is illegal
to
tamper with it.

Oh hell. My kit car is based on an old Triumph. I am installing a new engine
and I have chucked the old dials because they were full of water. I think I
have a note of the mileage. Oh well I'll have to sort something out.
Click to expand...
Tim appears to be from the UK, so he won't have any problem setting his
odometer to whatever he wants. He will only be breaking the law if he
tries to mislead anyone who buys the car.
--
Graham
 
in article bjamc.428$NK4.15358@stones.force9.net, Tim Fish at
timfishy@orange.net wrote on 5/5/04 13:24:

I'm building a kit car and I want to build a digital dashboard for it. I
have no problem with the rev counter (tacho) as I will just use a freq. to
voltage converter and feed that into a bar graph display driver.

The problem I have is when I come to the digital speed and other digital
displays like water temperature and oil pressure.

for speed I have a frequency coming in from a sensor
oil pressure, water temp and fuel I have resistances from the sensors.

Has anybody got any good ideas for converting these input signals into
numerical outputs?

my first thought is AD converter then convert this in a display driver
(LED).

But then I cant be too sure how these will be calibrated and things?

Thanks,
Tim




You might calibrate to two or three points, and most senders (autospeak for
Click to expand...
transducer) have published zero/full scale specs.
Things like oil press., coolant temp., and fuel level seldom need to be
displayed with any kind of absolute accuracy. Even their precision is
rarely more than 4-6 bits. An 8-bit precision (or accuracy) would be far
more than any driver could have a use for. Maybe if you're doing
performance optimization or racing data acquisition then go for it,
otherwise, why bother?
 
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