On 12/25/06, Japie <[EMAIL PROTECTED]> wrote:
Wow, what a responce, thank you all for your input!
For the "something went terrebly wrong" part we need accurate and fast
timings.
temp. readings and humidity are for engine adjustements so 500ms. will do,
Easy.
pressure readings for turbo boost and oil can contain info about a engine
crash so 100ms. at least.
Easy if it's only an A/D voltage reading
As for rpm readings it's problematic, if the engine is running 10.000rpm
the camshaft is doing 5000 so the "slowest" pulse I can get of it is 90
times per second, but I would like to know both the speed of the
crankshaft as the camshaft because after a blow-up it would be nice to now
if the engine was damaged because the cambelt broke or that the cambelt
broke because of the damage...
In the project I want to read the owfs with rrdtool and writing the rrd-db
rrd might not be a great fit. It expects a constant sampling rate and
throws out excess data. Why not just save the raw data?
to an usb-stick.
Is a stick fast enough? I suppose the OS will cache to RAM first.
This stick can be copied after a run for later use.
I'am planning on using the ASUS WL-HDD2.5 with openwrt/owfs/rrdtool, only
Using a hub works.
donwfall is that it has only one usb port so a hub is needed. (on the
other hand thats positive since I have all the hubs ports for 1wire so I
can use a single one for the fast timings of the crankshaft one for the
camshaft and another for temp. and pressure readings.) On openwrt I like
to place a webpage with rrd-images of the run so we can read-out the
values via wlan right after a run (or crash).
As for the sensors, DS2423 sounds great using a sample rate of 50ms. I
could use both crank and cam on one wire.
Are there any shematics around on how to hook it up to an magnetical or
optical pulse signal?
The DS2450 should be great for temp and pressure, every automotive sensor
gives 0-12v. so I could make a smal device converting 0-12 to 0-5 wich can
be used for every sensor.
The DS2450 can read the 4 voltages at once.
It really is 8 bit resolution (which might be sufficient, and if we modify
OWFS for that resolution, we can get sampling in under 3 msec).
As for humidity is there something usable available for that (since it's
placed inside the inlet channel wich is under 7bar pressure) or should
that be homebrew also?
Use the standard humifity sensor (DS2438-based) AAG used to make one in a
stainless steel enclosure that might be more appropriate for your use. I
have no idea of the effect of pressure or diesel fuel on the sensors.
And does anyone of you guys know some great documentation on how to hookup
and setup a 1wire system? (owfs itself is well documented as is openwrt)
See http://1wire.org/
--
Groetjes Japie
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