Paul,
I would gleefully welcome a kit of parts (reasonably priced) with
instructions, that I could assemble at home. It would hopefully include a
printed circuit board, PIC's, multiplexer, LCD, etc. ...and a some basic
software to get it up and running. Anyone else interested?
Mark Steitle
I am working on Finn. Unfortunately Finn does not need or like to work.
I know he can do it if we can talk him into getting off the beach.
Tracy is working up something as well. We will just have to wait.
Paul Lamar
Let me see if I can answer all the points you brought up in recent postings:
1) I'm now back on a fulltime job plus other obligations, so time is scarce. Paul, on
the other hand...
Sounds like you are in love. That will eat your lunch and then some.
2) You could expand the 8 channel PIC to 16 channels by using 2 CD4066 (Quad bilateral
switch), but since you want 10 bit resolution, the on-resistance becomes an issue
unless you add front end op-amps. Chip count is beginning to rise!
There are better parts than the CD4066 out there now. I just uploaded a partial data
sheet on a 16 channel analog switch with much better specs.
3) What schematic? Never got around to making a full schematic.
4) I don't mind sending you my source code, so you have something to laugh about.
My design philosophy had these points:
1) Cheap as possible (definitely had to be cheaper than analog gauges).
2) Minimum panel space
3) 1. lead to using components I had lying about (except for the display and the
AD817).
I'm quite happy with 8 bit accuracy (1% or so). Do you really need more for engine
monitoring? I haven't even bothered with calibrating my sensors (mostly because I don't
have the proper equipment) and use the nominal offsets and factors listed in the
pressure sensor datasheets.
Please realize that my set-up is very specialized. These are the parameters I display:
Oil pressure
Water pressure
Fuel pressure 1
Fuel pressure 2
Water temp
Oil temp before cooler
Oil temp after cooler
EGT 1
EGT 2
RPM (5 RPM resolution, from 12 pulses/rotation crank angle sensor coil)
MAP
Mixture (using an oxygen sensor)
Voltage
Left tank level (gallons) (home brewed capacitive sensors).
Right tank level (gallons)
Fuel flow
Fuel used
It's also so primitive that I have to burn a new EPROM if I want to change limits,
offsets or factors.
But you know: it works for me. Thus I have very little incentive to develop something
for production unless I have a guaranteed market.
Finn
Sounds good to me Finn. It would make a good article. Send me all the stuff
in crude form and I will work something up and submit it to EAA under
your name. I promise not to laugh at your code. I don't care how good
a programmer someone is. Code can ALWAYS be improved.
The article would be a good start for someone.
BTW do you know of a single chip that will do this?
It needs to be designed to take 4 bit wide LCD data and store it in an 8 bit wide flash
memory chip. This, as shown, would take two quad AND gates and an inverter.
I forgot. Is your LCD a four bit interface or an eight bit interface?
Paul Lamar
Forget this chip. I decided to use a PIC 16F877 instead and make the data
acquisition stand alone. It will interface to any 8 bit or a 4 bit standard
LCD interface and dump data in email mode to an RS232 serial PC port using
any email program such as NetScape or Internet Exploader. It will look just like
an external modem. Anybody have the Internet communication protocol
handy for email programs?
You will also be able to program it through the RS232 as to number of analog
channels you have and how often you wish to sample data using the email
program.
A $30 512K by 8 Flash memory chip would save 16 channels A/D three digits each channel
21,845 times. At a sample rate of once a second it would be 364 minutes or six hours.
A complete cross country flight's worth of data.
It would output the data in comma delimited ASCII form so it could be easily
imported into a spread sheet or data base program. The file size would be
several meg in comma delimited ASCII numbers and decimal points.
Put a connector on your EFIS LCD interface so this data acquisition system
will merely plug in.
This will also work as super low cost black box data recorder in the event
of a crash to help the NTSB figure out what happened.
Paul Lamar
The AirCraft Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site.
http://home.earthlink.net/~rotaryeng/ http://www.linux.org