Japie wrote: > Wow, what a responce, thank you all for your input! > > To make it a bit clear how "fast" the readings should be I will > explain some bits. Our engine is a diesel but we "homebrew" some > electronics so we can control common rail injectors instead of > ordinairy mechanical ones. The injectors uses 80v. 35a. to "unlock" > and 12v. 12a. for the real spraying so there will be some > interference so shielding has to be done. The engine is build for > full power only, so on the startline it will be throthled up to > 6000rpm and 80% (5bar) turbo pressure (wich can take up to 30 > seconds) before the clutch will be released and in the following 6 > seconds full throthle will be given and "hell brakes loose". :-) > (b.t.w. in a diesel puller the engine is "overfed" with diesel so > it's very very rich so using a lambda probe isn't really usefull, the > reason for this is that thick black smoke is a lot "heavyer" than > normal exhaust fumes therefore containing more energy so we can use a > bigger (read oversized) turbo wheel, example: > http://www.japie.deserver.nl/ftp/Hans_Boxler.wmv)
clearly this has been explored a great deal more than I understand. :) > > 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. All humidity sensors have an active surface that is vulnerable to grime. I would doubt you will get much more information inside the turbo about humidity than you will outside (no moisture coming or going there.) So with the outside air temp, the inlet air temp and the outside relative humidity (RH), you can compute/look up the RH at the inlet. To get absolute water content per unit volume, you need to have the pressure reading outside and the pressure differential at the inlet as well. You will want temperature and differential pressure in the turbo environment. Thermocouple temperature sensors shouldn't care about the nasty environment and you can do a j tube setup to keep the nasties away from the pressure sensor. > 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... Set it up with the pair of counters. When you get ready to go, take an initial reading with the engine stopped. Once this is stored, the counts for each one will increment as they get falling pulses. So if the cam reading is lower than the crank reading, the belt broke. If they are in sync, the belt died after the fact. You really don't want to be trying to count the pulses any other way. > > 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). I'm with Paul on this. Dump the data in raw form then fed that into rrd as a second stage. You only have a minute or two of data. > > 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. 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? See my comments above. > 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) Definitely start with the application notes from maxim-ic.com jerry ------------------------------------------------------------------------- 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
