Am Montag, 25. Dezember 2006 12:10 schrieb Japie: > > Data logging has 2 objectives, first is to find out why and where > something went terrebly wrong, second goal is to show us why the engine > was running so much bether one match than the other. > 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, > pressure readings for turbo boost and oil can contain info about a engine > crash so 100ms. at least. > Possible with the A/D converters and very small thermocouples, I think. Pressure sensors like this
http://www.datasheetcatalog.com/datasheets_pdf/M/P/X/5/MPX5100.shtml may fit, too. The conversion time of the DS2450 is about 1ms, so it fits these sensors. > 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... > Are you really sure it works that way? I would expect the cambelt to jump a few teeth in any case before you can measure any speed change in cambelt and shafts. My idea would be to have markings on the belt and the shafts, so one could check if the positions still fit. That would give a more meaningful result than checking for a secondary derived value like acceleration. Second, instead of checking speed of the engines shafts, I would check gas pressures to look for that situation. Gas pressure is directly joined with the engine's current situation, so is torque (but torque is hard to measure), speed in contrary is just a derived value. Maybe I'm wrong in details -- I'm just an electronics and energy engineer, not a mechanical engineer. If you have more insight, please let me know... > > In the project I want to read the owfs with rrdtool and writing the rrd-db > to an usb-stick. > 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 > 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 I found out, USB is a problem in environments where big EMC pulses from magnetic coils are present. It's twisted-pair, but still easy to break. > 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? > Just put a photo transistor between GND and the input line, and a 10k resistor between the Vdd and the input line, that should work. The chip counts negative edges, this way it will trigger on dark->light changes. Some debouncing is done inside the DS2423, if you need more, put a 1nF capacitor in parallel to the transistor. > 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? > Hm. As the common humidity sensors don't have any gases in them, pressure should not destroy them. However, their measurement results may be inaccurate as humid air behaves differently under low and high pressure conditions. > 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) > Read the official application nodes on the Maxim website. http://www.maxim-ic.com/an_prodline2.cfm/prodline/21 This one is especially useful for you, I think: http://www.maxim-ic.com/appnotes.cfm/appnote_number/148 Kind regards Jan -- People get annoyed when you try to debug them. -- Larry Wall ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
