http://forums.leaflabs.com/topic.php?id=514 A place to share, learn, and grow... en-US Fri, 22 Jan 2016 00:06:51 +0000 http://bbpress.org/?v=1.0.2 q http://forums.leaflabs.com/search.php http://forums.leaflabs.com/topic.php?id=514&page=4#post-12166 Fri, 03 Aug 2012 02:24:43 +0000 x893 12166@http://forums.leaflabs.com/ <p>Now success with port Microchip TCP/IP stack to STM32. Checked with MRF24BW module with HTTP and other services.<br /> <a href="http://akb77.com/g/stm32/home-automation-master-device/" rel="nofollow">http://akb77.com/g/stm32/home-automation-master-device/</a> </p> http://forums.leaflabs.com/topic.php?id=514&page=4#post-11932 Mon, 23 Jul 2012 06:48:21 +0000 x893 11932@http://forums.leaflabs.com/ <p>I use my own port for STM32 from Microchip library for MRF24WB (WiFi) and MRF89XA (MiWi). Not a hard to port but now can use all features for WiFi adn MiWi protocols. AsyncLabs very simplest. </p> http://forums.leaflabs.com/topic.php?id=514&page=4#post-2853 Sat, 27 Nov 2010 18:59:20 +0000 Silntknight 2853@http://forums.leaflabs.com/ <p>I think you are right about the time it spends near the horizon. That should be enough to get reliable Doppler information. Also, a little bit of playing around with trig can actually give me a reasonable height estimate from Doppler shift (isn't that exciting!) As long as I can track the Doppler shift as it arcs through the sky, I can get the dx/dt for the horizontal, which would be cosine of the (hopefully) circular trajectory. Related rates gives me the dx/dt for the vertical direction, or sine function. By finding the change in the Doppler shift, I get relationship between the sine and cosine rates. This depends, of course, on a localized circular trajectory, but it should follow that type of trajectory provided the trajectory was circular to begin with.<br /> Also, the time it spends visible in the sky would also give me a speed. If I know the speed, I know the height because of the equation for centripetal acceleration (a = v^2/r). Because the acceleration would have to be very close to 9.8, the radius minus the Earth's radius gives me the height.<br /> I'll check with the organizers to see if pressure sensing or temperature sensing counts. Maybe some other sensor, such as UV detection, would count. </p> http://forums.leaflabs.com/topic.php?id=514&page=3#post-2850 Fri, 26 Nov 2010 20:40:57 +0000 gbulmer 2850@http://forums.leaflabs.com/ <blockquote><p>Doppler shift works best when the object is moving directly toward the detector, not on a parallel line to the detector (or a perpendicular). </p></blockquote> <p>Agreed; Doppler works best when the object is travelling straight towards or away from the observer.</p> <p>At the equater a satellite at 100km altitude (to make the math easier) will appear above the horizon about 1,600km away, and sink below the horizon also at 1,600km away.<br /> A. 3,200km might be enough time to try to estimate doppler shift approaching and receding from the observer<br /> B. If the signal is identifiable as your satellite, the time it's 'visible' above the horizon will give an indication of altitude, and the time it is visible to a set of overlapping observers gives the path it follows.<br /> C timing, reasonably accuratley would give the orbit time, and hence the mean altitude can be derived.<br /> <a href="http://www.physicsclassroom.com/class/circles/u6l4c.cfm" rel="nofollow">http://www.physicsclassroom.com/class/circles/u6l4c.cfm</a><br /> D. ask the organisers to see iif they can offer some suggestions on proving the satellite wins. </p> http://forums.leaflabs.com/topic.php?id=514&page=3#post-2848 Fri, 26 Nov 2010 19:35:41 +0000 Silntknight 2848@http://forums.leaflabs.com/ <p>I'll be sure to ask because it could greatly simplify stuff.<br /> Also, I just noticed the price also... Unless I can get one donated, I think that my best option is to make something similar using key fobs for cars.</p> <p>Also, about Doppler shift, I'm not sure that would work in orbit because of the direction on travel. Doppler shift works best when the object is moving directly toward the detector, not on a parallel line to the detector (or a perpendicular). </p> http://forums.leaflabs.com/topic.php?id=514&page=3#post-2843 Fri, 26 Nov 2010 19:03:41 +0000 gbulmer 2843@http://forums.leaflabs.com/ <blockquote><p>Doppler shift can give me a speed, yes, but I'm not sure if that is a permissible form of tracking, because it "could" be lower than 99km, even if briefly.</p> </blockquote> <p>Ask the N-Prize organisers?</p> <blockquote><p>I actually hadn't seen the 5g transmitter you put the link for. That should be perfect actually. I wonder if it has solar cells built onto it. If so, then I have pretty much a complete setup.</p> </blockquote> <p>Ah.<br /> I was linking to it, because it seemed very close to a good spec./existence proof, but from your comment, you didn't look at the price, unless I misread it, it's over $3k :-( </p> http://forums.leaflabs.com/topic.php?id=514&page=3#post-2837 Fri, 26 Nov 2010 17:33:03 +0000 Silntknight 2837@http://forums.leaflabs.com/ <p>I can't really give an estimate right now actually, as I am not sure. I'll be doing the calculations later on. Doppler shift can give me a speed, yes, but I'm not sure if that is a permissible form of tracking, because it "could" be lower than 99km, even if briefly.<br /> I actually hadn't seen the 5g transmitter you put the link for. That should be perfect actually. I wonder if it has solar cells built onto it. If so, then I have pretty much a complete setup. </p> http://forums.leaflabs.com/topic.php?id=514&page=3#post-2825 Thu, 25 Nov 2010 09:39:57 +0000 gbulmer 2825@http://forums.leaflabs.com/ <p>I looked at the N-Prize site. I do remember it. There was quite a lot of interest at the time.</p> <p>I think any wireless signal will be sufficient, I don't think it needs to be as fancy as a car door code.</p> <p>I imagine you've seen this 5gram wireless system:<br /> <a href="http://www.microwavetelemetry.com/Bird_PTTs/5g.php" rel="nofollow">http://www.microwavetelemetry.com/Bird_PTTs/5g.php</a> </p> http://forums.leaflabs.com/topic.php?id=514&page=3#post-2824 Thu, 25 Nov 2010 08:53:52 +0000 gbulmer 2824@http://forums.leaflabs.com/ <p>Have you estimated how fast the satellite will be travelling?<br /> Won't Doppler shift be enough to calculate it's speed, and hence that it must be pretty high?<br /> The transmitted 'operate door lock code' from a car-door remote should be enough to demonstrate that the satellite is the one you sent, and it is the same one on 9 orbits. </p> http://forums.leaflabs.com/topic.php?id=514&page=3#post-2823 Wed, 24 Nov 2010 22:52:14 +0000 Silntknight 2823@http://forums.leaflabs.com/ <p>The URL is: <a href="http://www.n-prize.com/" rel="nofollow">http://www.n-prize.com/</a></p> <p>Well its good to know that I should be able to do 9 orbits on battery power with a really low baud. The real complication will be in writing software to calculate its position.</p> <p>As far as money goes, the cost will be mostly in a few parts I can't get free- reinforced cylinders (for the ethanol stage), propellant material (for the SRB stage), and the electronics. Actually, in case no one saw, SparkFun's 2nd(?) annual free day is coming up and I plan to make the most of it. I guess that raises my budget to $200 technically, but its close. If everything fails, I would have made a really cool firework at least. </p> http://forums.leaflabs.com/topic.php?id=514&page=3#post-2818 Wed, 24 Nov 2010 14:24:25 +0000 gbulmer 2818@http://forums.leaflabs.com/ <blockquote><p>12 baud seems almost excessive for triangulation</p> </blockquote> <p>As I wrote, if you can reduce that by a factor of 100, then I believe the tranmitter power is reduced by 10x.</p> <blockquote><p>Trust me, I can get this done on $100.</p> </blockquote> <p>Great! Please tell me when it is about to happen.<br /> One of my chums was/is a coordinator/technical lead for the software development which integrates the world-wide educational/'amateur' satellite ground stations into a global network (genso), so he'll probably be getting some sites to tune in to you. I'd be excited to go over to his facility and 'listen live'.</p> <blockquote><p>It's actually a British sponsor, so £999.99.</p> </blockquote> <p>What's the URL? I didn't go to this years UK AMSAT meeting, so I think I have missed this. </p> http://forums.leaflabs.com/topic.php?id=514&page=3#post-2812 Wed, 24 Nov 2010 09:51:41 +0000 mbolivar 2812@http://forums.leaflabs.com/ <p>Also, here's a note on the SaikoLED webpage about firmware for Arduino or Maple:<br /> <a href="http://saikoled.com/downloads/" rel="nofollow">http://saikoled.com/downloads/</a> </p> http://forums.leaflabs.com/topic.php?id=514&page=3#post-2811 Wed, 24 Nov 2010 09:48:50 +0000 mbolivar 2811@http://forums.leaflabs.com/ <p>soundcyst:</p> <blockquote><p> and,</p> <p> perry's got LEDs hooked up to a maple+wishield that go through the color wheel when the wireless network is up. makes it easy to tell when it's down :)</p> <p>so this means the wishield library ports nicely then? (or maybe even "just works"?) </p></blockquote> <p>Well, it ported, at least. He was among the people that did the software for SaikoLED:<br /> <a href="http://saikoled.com/products/" rel="nofollow">http://saikoled.com/products/</a></p> <p>(So their website's claim that it was "based on the Arduino platform" is a little misleading, hehe -- some non-LeafLabs folks at the company decided to switch to Arduino, but all of the initial work was done on Maple).</p> <p>You can check out the "wishield-dev" and "lights" branches on his github libmaple fork:<br /> <a href="https://github.com/iperry/libmaple/tree/lights/libraries/WiShield/" rel="nofollow">https://github.com/iperry/libmaple/tree/lights/libraries/WiShield/</a><br /> <a href="https://github.com/iperry/libmaple/tree/wishield-dev/libraries/WiShield" rel="nofollow">https://github.com/iperry/libmaple/tree/wishield-dev/libraries/WiShield</a></p> <p>We're aiming to include these in IDE 0.0.9 (which will include alpha support for the serial bootloader we're currently debugging) or 0.1.0 (which is the ground-up rewrite expected around Dec. 15, although that realistically might slip). </p> http://forums.leaflabs.com/topic.php?id=514&page=3#post-2795 Mon, 22 Nov 2010 19:10:42 +0000 Silntknight 2795@http://forums.leaflabs.com/ <p>Well, as much as I love them, planes are slightly off-topic.<br /> Trust me, I can get this done on $100. I know plenty of ways to get some free materials for most of the housings (including much of the launch gear). If I really needed to, I could go up to $1600 and stay within the competition rules. It's actually a British sponsor, so £999.99.<br /> The satellite, as its name suggests, is intended for 9 orbits, thus the need for communication. I need to verify its location. I don't care about data rate as long as it provides detectable pulses that I can use for triangulation. 12 baud seems almost excessive for triangulation.<br /> For power, I will stick to batteries. I was also thinking about whether or not solar cells would really be worth it for 9 orbits. </p> http://forums.leaflabs.com/topic.php?id=514&page=3#post-2793 Mon, 22 Nov 2010 16:56:07 +0000 gbulmer 2793@http://forums.leaflabs.com/ <p>I can't remember the equation (maybe never understood it?), but there is a quantified relationship between data rate (I guess modulation), carrier frequency, and power/signal strength.</p> <p>You can trade one for another. So data rate can be reduced to increase propagation distance without having to increase power. </p> <p>I think, in free-space, power falls as the square of the distance (radius), so going from 250m, 0.25km, to 99km, power is reduced by ~ 99^2 =~ 10,000 times less. So data rate would have to be reduced by a similar ratio, to balance the equation.</p> <p>So, to transmit (and receive:-) over 99km, even line of sight, in a legal band, with legal transmitter energy the data rate may have to be very low. CU Spaceflight said they have received signals at 600km, but, I think they said the data rate was about 12 baud.</p> <p>Some ready-made transmitters can't go that slow. </p>