[00:07] night [00:11] edmoore|away (~836ff570@gateway/web/freenode/x-sytrpbbzcxuqfjtw) left irc: Ping timeout: 252 seconds [00:17] fixed landing prediction [01:08] JohnTed (unstable@tor/regular/sid) left #highaltitude. [01:12] Tomorrow, I am going to embark on a shitty path loss predictor. [01:13] isn't path loss fairly well defined as far as humidity, distance, frequency etc go? [01:14] yes [01:14] I meant over terrain [01:14] aah, okay [01:14] so given two lat/lon/alt positions, it looks up elevations and does the sums. [01:15] It's somewhat hacky as it involves parsing 180M files in awk for every sum. [01:16] a lot [01:17] does it take long? [01:18] bout a second on a c2d laptop [01:18] nice [01:18] for some preliminary 'how bad might this be' tests [01:18] without the actual sums - which are easy [01:31] GeekShad0w (~Antoine@173.178.204-77.rev.gaoland.net) joined #highaltitude. [01:33] GeekShadow (~Antoine@reactos/tester/GeekShadow) left irc: Ping timeout: 240 seconds [01:42] GeekSh4dow (~Antoine@173.178.204-77.rev.gaoland.net) joined #highaltitude. [01:44] GeekShad0w (~Antoine@173.178.204-77.rev.gaoland.net) left irc: Ping timeout: 245 seconds [02:13] GeekSh4dow (~Antoine@173.178.204-77.rev.gaoland.net) left irc: Read error: Connection reset by peer [02:17] smealum (~smealum@smea.servebeer.com) left irc: [02:22] ms7821 (~Mark@flat.ms) joined #highaltitude. [02:42] natrium42 (~natrium42@CPE000625d867e2-CM0014045885be.cpe.net.cable.rogers.com) left irc: Ping timeout: 245 seconds [04:23] natrium42 (~alexei@CPE000625d867e2-CM0014045885be.cpe.net.cable.rogers.com) joined #highaltitude. [05:04] ms7821 (~Mark@flat.ms) left irc: Disconnected by services [05:04] ms7821_ (~Mark@flat.ms) joined #highaltitude. [06:24] p1nky (pinky@static-71-244-60-125.dllstx.fios.verizon.net) left irc: Quit: leaving [06:41] natrium42 (~alexei@CPE000625d867e2-CM0014045885be.cpe.net.cable.rogers.com) left irc: Ping timeout: 256 seconds [06:42] natrium42 (~alexei@CPE000625d867e2-CM0014045885be.cpe.net.cable.rogers.com) joined #highaltitude. [07:02] Simon-MPFH (~simon@phantom.mpfh.co.uk) joined #highaltitude. [07:26] natrium42 (~alexei@CPE000625d867e2-CM0014045885be.cpe.net.cable.rogers.com) left irc: Quit: My other car is a cdr. [07:47] Nick change: ms7821_ -> ms7821 [08:25] Endeavour (~Endeavour@r74-192-221-200.bcstcmta02.clsttx.tl.dh.suddenlink.net) left irc: Quit: Endeavour [08:34] b3cft (~abrock@nat/yahoo/x-zyyqievmqshwhytb) joined #highaltitude. [08:39] MikeMc68, you around [08:39] ?> [08:40] rjharrison (~rharrison@62.49.185.11) joined #highaltitude. [08:41] hi rjharrison [08:45] ei7ig_laptop (~j0n@2001:770:20:2:217:f2ff:fec4:58a4) joined #highaltitude. [08:57] Hey juxta [09:14] edmoore (~836f0142@gateway/web/freenode/x-khmmbrklhmvscrmd) joined #highaltitude. [09:26] Laurenceb (~laurence@host86-141-239-7.range86-141.btcentralplus.com) joined #highaltitude. [09:27] icez (~icez@unaffiliated/icez) left irc: Remote host closed the connection [09:30] ping edmoore [09:31] hi [09:31] http://www.robertharrison.org/listen/poll.php?callsign=horus&missionid=86&lastid=1 [09:31] This is the polling script [09:31] nice [09:32] (save for newlines! ) [09:32] If you look at the id and change it at the end it will pull back only new data [09:32] Yep I thought about that but this is for machine use so \nl is better than
I'm guessing [09:33] I guess it could be processed out the
[09:33] sure [09:34] Any thoughts do you think the BR should be there [09:35] missionid=0 or just not there is the current mission [09:35] the simplest is http://www.robertharrison.org/listen/poll.php?callsign=atlas [09:36] This will give all the data from the current launch for atlas [09:36] now technically i should be quite easy to say http://www.robertharrison.org/listen/poll.php?callsign=horus&format=kml [09:37] This could then be viewed in google maps [09:37] Is there a need for that ? [09:40] edmoore I guess this data can be pulled into the predicitor to give continuous predictions for landing [09:41] Well say updated every five minutes [09:41] sure. though the predictor can run pretty fast [09:41] perhaps once per status packet [09:41] 5 seconds fine my me [09:41] by [09:41] 5 mins is a bit slow, especially suring descent when you want really up-to-date data [09:41] Yep [09:42] Ajax on a google map constantly plotting a new landing spot would be good [09:43] This should open the data up. I'm going to add a whole load of fields to this in a bit fixed ones such as temp_int, temp_ext, pressure and custom_1...custom_10 [09:44] The frixed fields are usefull for comparisons between all launched where data is available [09:44] The custome 1-10 can contain what the hell you like [09:53] right, lectures. going to only be sporadic today [09:53] Nick change: edmoore -> edmoore|lectures [09:59] hey fergusnoble [09:59] How are you doing? [09:59] fergusnoble (~fergusnob@fn217.quns.cam.ac.uk) left irc: Quit: fergusnoble [09:59] Not well obv. :) [10:00] I've added some stuff to the line of sight calculator [10:01] so you can enter horizon elevation now [10:08] smealum (~smealum@smea.servebeer.com) joined #highaltitude. [10:15] hsmith (~chatzilla@62.49.157.204) joined #highaltitude. [10:45] hey juxta [10:55] laurence_ (~laurence@host86-141-239-7.range86-141.btcentralplus.com) joined #highaltitude. [10:57] Nick change: laurence_ -> Laurenceb_ [10:59] Laurenceb (~laurence@host86-141-239-7.range86-141.btcentralplus.com) left irc: Ping timeout: 248 seconds [11:01] hey MikeMc68, rjharrison [11:01] back now, was making/eating dinner :) [11:23] Simon-MPFH (~simon@phantom.mpfh.co.uk) left irc: Quit: Leaving [11:26] juxta np [11:26] How is it going> [11:26] ? [11:26] good good [11:26] still playing around with ideas for this board in eagle [11:26] not sure if I should try to put everything on the one board or perhaps seperate it a bit [11:27] junderwood (~John@adsl.jcu.me.uk) joined #highaltitude. [11:28] juxta both approaches have adv / diss [11:28] hm [11:28] Not much help I know [11:28] I planning on having an AVR for the main processor [11:28] :) [11:28] My favorite [11:28] and something else which I can offload telem too [11:29] probably just another atmega, but maybe an attiny [11:29] the 328p's are cool [11:29] Yep the tiny is fine too [11:29] yeah, the 328 is what I have here [11:29] I think I'm going that way too something to drive the radio [11:29] that way I can get data etc more frequently [11:29] as it'll be logging to SD [11:30] This leaves the avr available for logging and keeping an eye on the sensors [11:30] :) [11:30] Yep [11:30] I dont have any attinys though [11:30] One could ask how often do you need the data logged but I like the approach [11:30] and I dont have an AVR programmer [11:30] so I might just use another 328 [11:30] AVR programmer = quite cheap [11:30] cause I have lots of them [11:31] 328's are cool that's what I have on icarus [11:31] icarus III [11:31] rjharrison, yeah, but serial on an attiny is probably going to be a pain, I dont know what the situation with libraries is on those chips [11:31] I've only used the 328 with the arduino libraries [11:32] do you have a photo of icarus III btw? I think I saw one once, it's all SMD, right? [11:32] http://www.robertharrison.org/images/various/Icarus%20III%20-%20Breadboard%20Prototype.JPG [11:32] That's the prototype [11:32] On sec and I'll take a recent picture [11:33] what pressure senor are you using? [11:35] I was going to ask the same thing :) [11:35] http://www.robertharrison.org/svn/filedetails.php?repname=the-icarus-project&path=%2FIcarus+III%2Fdatasheets%2FFreescale-Diff-PSensor-MPXV5004DP.pdf [11:36] ah [11:36] I've been looking at a similar one - the MPX5100D [11:37] yours has a better range though [11:37] interesting [11:37] I was thinking of using it for a pitot sensor [11:38] but decided the drift was too high [11:38] oh wait [11:38] 0-3.92 kPa? [11:41] rjharrison, still about? [11:42] yep [11:42] http://www.robertharrison.org/images/icarus3/Icarus%20III.JPG [11:42] Bit big but this is it [11:43] Yep it's a differential pressure sensor [11:43] ah brilliant! [11:43] rjharrison - what's the go with differential sensors, how do they work exactly? [11:43] I want to measure the difference between the balloon internal pressure and the local atmos. [11:43] how do you convert that to a useful range? [11:43] ohh [11:43] I okay [11:43] I see* [11:44] where the pcb from? [11:44] Olimex [11:44] ah [11:45] so you have 5v and 3v3 power onboard I guess rjharrison [11:45] Yep [11:45] Hence the two power connectors [11:45] and you just send the atmega 5v to the ref voltage pin? [11:45] Though they can me linked and powered from a single source [11:46] Actually I use a divider to move it down to 3.3v [11:46] and ref on 3.3 [11:46] ah okay [11:46] is there a limitation that stops you from using 5v as the reference voltage? [11:47] Yep [11:47] or is the divider for simplicities sake? [11:47] Vref can't me more than 0.3 Vcc IIRC [11:47] http://www.robertharrison.org/svn/filedetails.php?repname=the-icarus-project&path=%2FIcarus+III%2Feagle%2FIcarus+III%2FIcarus.pdf [11:48] Right I need to feed my kids back in a bit [11:48] whats vref? [11:57] http://media.armadilloaerospace.com/2009_11_03/2009_11_03_2959_ft_boosted_hop.wmv [11:57] ^ nice [12:01] WOW!! [12:20] boo [12:24] Action: SpeedEvil wants one. [12:30] whoa, that's nice [12:33] GeekShadow (~Antoine@reactos/tester/GeekShadow) joined #highaltitude. [12:33] Laurenceb_: where is that? [12:48] texas [12:50] hsmith (~chatzilla@62.49.157.204) left irc: Ping timeout: 264 seconds [12:56] bbl [13:01] Laurenceb_ (~laurence@host86-141-239-7.range86-141.btcentralplus.com) left irc: Ping timeout: 256 seconds [13:03] Hey juxta you still outthere [13:03] sure am [13:05] Been playing with extracting data from the listener [13:05] ah right, with the socket? [13:05] I'm hoping to be able to allow people to pull data into there own apps [13:05] Well via http atm [13:06] for example [13:06] oh, from the listener, i see, I thought you meant fldigi :) [13:06] http://www.robertharrison.org/listen/poll.php?callsign=horus&missionid=86&lastid=61937&format=html [13:06] yeah I saw a big page of coords before [13:06] This is your flight data [13:06] ahh, nice :D [13:07] There is a bit of early data in there which I need to pull out [13:07] If you pass in a lastid you will only get more recent data back than your last id [13:07] Does that make sense? [13:07] the id is the first column [13:07] yep [13:08] http://www.robertharrison.org/listen/poll.php?callsign=horus&missionid=86&lastid=62550&format=html [13:08] This gives teh last 10 ish data points [13:08] yeah [13:08] what's the ID? just a sequential number? [13:08] Yep [13:09] Given by the server [13:09] ah right [13:09] it would be handy to have a way to grab say the most recent 5 packets etc [13:09] If I take two lat/lon pairs - if I take a point x% along each difference between lat-lon - does this describe a great circle? [13:11] Yep good point [13:11] hey rjharrison - why did you omit the mounting holes on icarus 3? didn't end up using them? [13:11] Will work on that too [13:12] juxta yep I never used them [13:12] I'm thinking I probably wont use mounting holes either, so I'll forgo them I think [13:12] You can't mount to polystyreene very easily [13:13] Sure you could stick sime balsa wood in there but I quite like to take the board in and out [13:13] also - that ham Adrian who's been helping me has a bunch of etching gear, a lighbox to expose boards, might give it a shot and see if I can make it manually - just gotta drill all the holes after [13:13] yeah, I'd rather just wedge it in with a bit of foam or something [13:14] Yep the word fuck that come to mind :) [13:14] btw - what sort of filter do you use in front of your cam? [13:14] But go for it [13:14] haha [13:14] Just a uv filter [13:14] yeah it seems a little tedious [13:14] a decent hoya? or just a cheapo? [13:14] I would like to remove some blue light (haze) too [13:14] Perhaps a blue filter on a launch in the future [13:15] I used a $5 ebay job on mine, i'm thinking it may not have helped with the reflections of the cam itself [13:15] All the pictures come back very blue to me [13:15] I think flush with He next time and put less He in the balloon You'll get the pics you want [13:15] A hoya [13:15] yeah [13:16] either that or leave the cam open to the atmosphere I guess [13:16] It was clearing nicely just b4 burst [13:16] yeah it was, bit of a shame :( [13:16] You going to launch again soom? [13:16] Son [13:16] Soon even [13:17] hoping to [13:17] might make up a payload tomorrow if I have some time [13:17] Ooh [13:17] no photos on this one I dont think, just a small one [13:17] Tracker then [13:17] yeah [13:17] tracker for sure [13:18] Be interesting to see if you can resist the temptation to send the camera [13:18] I have done one launch without so far [13:18] I think I will also put something with CHDK onboard in next time [13:18] triggering manually is a bit of a pain, also you dont have the option for video etc so easily then [13:18] Yep that is cool and even better you can control the camera via USB pulses [13:19] yeah that would be cool [13:19] I'll see if my friend will sell me his a570 :) [13:20] rjharrison - did you get your board layout right first time around? or did you have to have it re-made at all to fix errors? [13:21] Well there is one error on the pcb but yep right first time [13:21] But build a prototype [13:21] will do [13:22] what error is there? [13:22] I was missing an R to ground [13:22] But I fixed it by soldering one to a GND via and the point where I need it [13:23] ah okay [13:23] did you manually route yours boards too? [13:23] Back to the F that [13:23] edmoore|lectures swares by it and he's right [13:24] yeah natrium was telling me not to autoroute too, haha [13:24] But I just manual route the bits I don't like and let autorouter to the rest [13:24] that's what i've been doing so dar also [13:24] far* [13:24] Life is too short [13:25] I used a groun plane on this board which is a good thing I believe [13:26] You can see the fix on the image top left of the atmega chip there is an R at an angle [13:27] yeah, and it looks like a resistor/cap soldered in at a funny angle? [13:28] Yep R [13:29] Lucky the via was there [13:29] hehe [13:29] This pulls the current off the FET to allow it to turn off again [13:29] did you solder the atmega by hand? [13:29] I fixed the design file though [13:30] There are a few other things I want to do. Like break out the rest of the pins [13:31] I'm thinking I'll do that also [13:33] rjharrison, I bought a couple of ublox modules to use by the way [13:39] Cool JC rate them and I like them too [13:39] Exp that one with the antenna on it [13:40] this is the one I got: [13:40] http://www.esawdust.com/product/egps-fsa03-module/ [13:47] Very nice [13:47] I want one of those :) [13:48] The lassen is fine but that has everything on it [13:49] yeah [13:49] well priced too [13:49] Yep very its 40 quid here in the uk [13:53] hmm [13:53] the autorouter seems to fail on some very trivial things [14:00] rjharrison, if you're still there, what's the part name for those screw terminals in eagle? [14:13] GeekShadow (~Antoine@reactos/tester/GeekShadow) left irc: Read error: Connection reset by peer [14:14] N900evil (~Speedevil@tor/regular/SpeedEvil) left irc: Quit: Leaving [14:14] N900evil (~Speedevil@tor/regular/SpeedEvil) joined #highaltitude. [14:20] sbasuita (~sbasuita@unaffiliated/drebellion) joined #highaltitude. [14:23] Ahh I made them [14:23] They are in my eagle file in the svn [14:28] ping juxta [14:28] cheers rjharrison [14:29] Paste this into the google map search box [14:29] http://www.robertharrison.org/listen/poll.php?callsign=horus&missionid=86&format=KML [14:29] nice work :) [14:30] in hindsight we were pretty luck that didn't cross the river before landing [14:30] lucky* even [14:31] there are only 2 places cars can cross - Murray Bridge (south), or Mannum (north) [14:35] Ooh [14:35] Lucky [14:36] This will allow us to some fun things with the data in the future hopefully [14:39] Nick change: edmoore|lectures -> edmoore [14:40] Yo edmoore [14:40] polling working now [14:41] if you paste this into google maps you will get the path of horus http://www.robertharrison.org/listen/poll.php?callsign=horus&missionid=86&format=KML [15:05] edmoore et al http://ukhas.org.uk/projects:dlistener#server [15:06] New info about getting data from the server via http [15:11] ok cool, awesome work [15:11] sorry for being unresponsive btw, just in the lab doing project [15:17] edmoore np [15:48] juxta (fourtytwo@ppp121-45-84-224.lns20.adl6.internode.on.net) left irc: Ping timeout: 240 seconds [16:10] Lunar_Lander (~lunar_lan@p54884AFD.dip.t-dialin.net) joined #highaltitude. [16:10] hello [16:11] hi Lunar_Lander [16:11] ping ei7ig ei7ig_laptop [16:12] You have left your pc on still running fldigi if you havn't realised :) [16:16] Simon-MPFH (~simon@phantom.mpfh.co.uk) joined #highaltitude. [16:31] Simon-MPFH (~simon@phantom.mpfh.co.uk) left irc: Quit: Leaving [16:32] hi rjharrison [16:32] was in a meeting. [16:32] yup. I was using it for CW decoding this morning before I came to work. [16:38] Lunar_Lander (~lunar_lan@p54884AFD.dip.t-dialin.net) left irc: Ping timeout: 272 seconds [16:50] ei7ig_laptop (~j0n@2001:770:20:2:217:f2ff:fec4:58a4) left irc: Quit: ei7ig_laptop [16:55] Lunar_Lander (~lunar_lan@p54884AFD.dip.t-dialin.net) joined #highaltitude. [16:55] hello again [16:55] hi [16:55] laptop simply shut down [16:55] Endeavour (~Endeavour@r74-192-221-200.bcstcmta02.clsttx.tl.dh.suddenlink.net) joined #highaltitude. [16:57] sbasuita (~sbasuita@unaffiliated/drebellion) left irc: Read error: Connection reset by peer [17:09] Endeavour (~Endeavour@r74-192-221-200.bcstcmta02.clsttx.tl.dh.suddenlink.net) left irc: Quit: Endeavour [17:19] edmoore (~836f0142@gateway/web/freenode/x-khmmbrklhmvscrmd) left irc: Ping timeout: 252 seconds [17:27] GeekShadow (~Antoine@reactos/tester/GeekShadow) joined #highaltitude. [17:28] Professor (nobody@nerdhouse.org) joined #highaltitude. [17:28] Professor (nobody@nerdhouse.org) left #highaltitude. [17:30] Lunar_Lander (~lunar_lan@p54884AFD.dip.t-dialin.net) left irc: Ping timeout: 272 seconds [17:31] hsmith (~chatzilla@62.49.157.204) joined #highaltitude. [17:31] jcoxon (~jcoxon@host86-156-36-88.range86-156.btcentralplus.com) joined #highaltitude. [17:36] LazyLeopard (~irc-clien@chocky.demon.co.uk) joined #highaltitude. [17:36] Lunar_Lander (~lunar_lan@p54884AFD.dip.t-dialin.net) joined #highaltitude. [17:47] sbasuita (~sbasuita@unaffiliated/drebellion) joined #highaltitude. [17:49] hi jcoxon [17:50] b3cft (~abrock@nat/yahoo/x-zyyqievmqshwhytb) left irc: Quit: laters potaters [17:50] hey Lunar_Lander [17:51] how's life? [17:53] ei7ig_laptop (~j0n@2001:770:132:dead:217:f2ff:fec4:58a4) joined #highaltitude. [17:55] Ping jcoxon [17:55] hey rjharrison [17:55] Lunar_Lander, not bad thanks [17:55] ei7ig have you turned off your fldigi? [17:55] jcoxon you got 5 4 a call [17:55] mine too [17:56] rjharrison, yup [17:56] Skype or normal [17:56] I tried out BalloonTrack by EOSS [17:56] it also looks interesting as a prediction program [17:57] jcoxon skype or normal [17:58] skype is no problem [17:59] Hi James [18:00] ?hello hsmith [18:22] N900evil (~Speedevil@tor/regular/SpeedEvil) left irc: Ping timeout: 245 seconds [18:25] edmoore (~50b1972a@gateway/web/freenode/x-xeclyfcsiiokyzmw) joined #highaltitude. [18:26] hsmith (~chatzilla@62.49.157.204) left irc: Ping timeout: 260 seconds [18:37] icez (~icez@unaffiliated/icez) joined #highaltitude. [18:40] N900evil (~Speedevil@tor/regular/SpeedEvil) joined #highaltitude. [18:43] edmoore (~50b1972a@gateway/web/freenode/x-xeclyfcsiiokyzmw) left irc: Ping timeout: 252 seconds [18:48] junderwood (~John@adsl.jcu.me.uk) left irc: Read error: Connection reset by peer [18:49] junderwood (~John@adsl.jcu.me.uk) joined #highaltitude. [18:54] Hiena (~Hiena@81.93.195.181.datatrans.hu) joined #highaltitude. [18:55] 'evening! [18:55] How the thing goes up? [19:09] edmoore (~836f0142@gateway/web/freenode/x-dxbaodbwxcgxphjc) joined #highaltitude. [19:16] hey Hiena [19:16] evening edmoore [19:16] hi [19:17] fully recovered from the ball? [19:17] yep thanks [19:17] was fine on sat [19:17] berocca is the key [19:19] :-) [19:22] edmoore (~836f0142@gateway/web/freenode/x-dxbaodbwxcgxphjc) left irc: Ping timeout: 252 seconds [19:23] smealum (~smealum@smea.servebeer.com) left irc: Ping timeout: 252 seconds [19:24] jcoxon (~jcoxon@host86-156-36-88.range86-156.btcentralplus.com) left irc: Quit: Leaving [19:28] N900evil (~Speedevil@tor/regular/SpeedEvil) left irc: Ping timeout: 245 seconds [19:30] Hiena (~Hiena@81.93.195.181.datatrans.hu) left irc: Quit: -=Got bored from the net. Gone blowing up things.=- [19:38] edmoore (~836f0142@gateway/web/freenode/x-ujepzlryowokfhxf) joined #highaltitude. [19:51] Xenion (~robert@p57972494.dip.t-dialin.net) joined #highaltitude. [19:53] N900evil (~Speedevil@tor/regular/SpeedEvil) joined #highaltitude. [19:53] Evening all [19:54] Xenion (robert@p57972494.dip.t-dialin.net) left #highaltitude. [20:05] evening rjharrison [20:06] hehe [20:06] Hows it going [20:06] fine and you? [20:06] Yep looking forward to getting my own payload up again [20:06] nice [20:07] I have a physics exam tomorrow [20:07] oooh [20:07] Lunar_Lander: bad luck :( [20:07] what sort of stuff is it on? [20:08] edmoore do I need to liase with anyone re the polling of data [20:08] probs not. or at least, no one else is organized enough to through cycles at it yet :) [20:08] brain cycles, that is * [20:08] hehe ok cool [20:09] Basically the data is there and ready now for use in a real time predictor [20:09] it is Experimental Physics 1 [20:09] so it is mechanics and some thermodynamics [20:10] Given most sentences take 30 seconds to come in I woudl suggest an initial poll of 60 secons [20:11] Lunar_Lander: i don't enjoy you. I was never much good at either mechanics or thermodynamics [20:12] s/enjoy/envy [20:12] yes [20:12] I wonder how it will be [20:12] they' [20:13] they'll give 10 tasks, each worth 12 points [20:13] RocketBoy (~Steve@217.47.75.8) joined #highaltitude. [20:13] and 36 are required to pass [20:22] junderwood (~John@adsl.jcu.me.uk) left irc: Read error: Connection reset by peer [20:22] junderwood_ (~John@adsl.jcu.me.uk) joined #highaltitude. [20:26] Laurenceb_ (~laurence@host86-141-239-7.range86-141.btcentralplus.com) joined #highaltitude. [20:32] hello [20:32] Hello_. [20:32] hi SpeedEvil_ [20:33] Action: SpeedEvil just found out his phone won't get a wifi signal in the oven. [20:33] (I was pondering using it to observe bread rising. [20:33] I was looking at anemometer stuff some more - the vishay 0603 pt100 is made of alumina [20:33] heh [20:33] On balance it was probably a silly idea. [20:33] alumina and win! [20:33] interesting. [20:34] the conductivity/heat capacity figure is very good [20:34] compared to the glass the leaded sensors use [20:34] What is the roder of magnitude if you use something crap - say a solid 0603 thermistor [20:34] Have you done the numbers for that? [20:34] yes [20:34] its works ok just stuck on a pcb [20:34] ~15hz bandwidth [20:35] but you need to surround it with a ground plane to mop up the stray heat [20:35] hmm [20:35] the tricky bit is getting accuracy and reducing power consumption [20:35] possibly time to try a pcb with several approaches on. [20:35] and see which works best [20:35] yeah [20:36] how much are the 0603 pt100s? [20:36] �1.49 in single unit [20:36] not bad at all [20:37] are there any thin-film thermistors? [20:37] but I suppose savings once you get at that level are pointless mostly [20:37] thermistors tend to have poor tolerance [20:37] at least for a first run [20:37] compared to pt100 [20:37] yeah - but if you're servoing the resistance, you don't care [20:37] also nonlinear [20:38] you want to keep it x degrees above air temperature ideally [20:38] not at just x degrees [20:38] ah [20:38] that way the heat loss by conduction through the pcb is constant [20:38] I see. [20:39] at the moment I'm thinking two pt100 sensors in a bridge with high tolerance resistors [20:39] or a 0401 resistor with a mini thermocouple glued onto the bottom [20:40] the second approach gives really low current draw [20:40] <1ma @3.3v [20:40] hmm [20:40] but is fiddly [20:40] yes [20:40] easy if you have a nice little machine making 100k of them [20:41] noit so much if you're swearing at it under a microscope [20:41] with two pt100 sensors I'm worried about resistor drift [20:43] the delta temperature is limited by how much current you can use [20:43] about 1K/ma @3.3v in the 0 to 15m/sec airspeed range [20:43] presumably at some point they'll get nonlinear - due to assymetric heating [20:44] pt100 is about 3100ppm/K [20:44] so say 10K is the delta T, thats 3.1% [20:44] so you need at least 0.1% resistors for decent performance [20:45] why [20:45] and I'm not sure how much they drift [20:45] if you've got a micro uin there [20:45] in [20:45] yeah you can calibrate [20:45] but resistors drift as they age [20:45] but you can calibrate that out if you have a zero wind mode surely? [20:46] maybe, ideally you want a few calibration points [20:47] I was just thinking thermocouple avoids these problems entirely [20:47] thermocouples have their own issues of course [20:48]