The capacity of Lithium batteries varies by brand, chemistry and construction, but here is a comparison graph for the "Ultralife" battery. You can find these at discounted prices online, but remember that lithium batteries have to be shipped via ground service. These are primary lithium cells (not rechargeable).
Do you know how to estimate the battery life for your project?
I flew that XBee/MAWD device today, on an I245G motor in a 4" rocket. I set up the receiving station about 125 feet from the launchpad. It worked perfectly, with a nice flow of data through the entire flight. It flew to about 1580 feet. The data stopped nicely right after landing. Everything seems to have worked as I'd hoped, and apparently regular XBee Pro (Series 1) modules are enough for this purpose. I'm absolutely thrilled. I'm so glad this thread is here - it got me off my backside and working on this.
Mr. Allen, · I don't think·I·know how to estimate the battery life for our project. How do you estimate the battery life? Does the Ultralife battery·last longer than the normal lithium batteries? Do they make rechargeable lithium or Ultralife batteries? · Appreciate all your time and help, · Sean from ARLISS-NH
Tracy Allen said...
Sylvie, I can see a followup article is in preparation! That's great!
You'll get a special thanks in the article, as I'm using the code you posted here in my receiver program. I'll probably write this up for publication in Sport Rocketry, the magazine of the National Association of Rocketry, or possibly for Extreme Rocketry (which pays authors <grin>).
This opens up a LOT of possibilities. It'd be easy to make a version that sent down data from various sensors rather than from the MAWD. It'd be pretty easy to have control in the other direction as well - to send signals from the ground up to the rocket.
I'm going to try to hitch a ride on someone else's larger rocket in a few weeks, and fly the thing higher, to 3000 feet or so, to better test the range. I was probably about 2000-2500 feet from the rocket at the furthest point (1600 feet up, some distance downrange), and I never did lose contact with it. Could I get a mile of range from a standard XBee Pro, when it's way up in the air above me? We'll find out.
I don't think it'll work on a rocket going to 10K or 15K feet, though, but one of the 900MHz versions might, and one with a special antenna on at least one end (receiver or transmitter) very likely would.
@Tom, you have to add up the current drawn by the individual components of you project. Don't leave anything out. For example,
total mA
= 2 milliamps for the Stamp
+ ? mA for power LED on the BOE
+ ? mA for the Sensirion
+ ? mA for the USB datalogger
+ ? mA internal for the 5 volt regulator
+ ? ...
Then you divide the battery capacity from its data sheet by the total current. Battery capacity in mA-hours, divided by mA, comes out with hours.
Actually, it is not quite that simple. There are a couple of things.
You have to be conservative about the battery capacity, particularly if there is anything on board that draws a lot of current. When battery companies tell you the capacity, it is to a voltage level and with a certain current drain, and it is usually a voltage level too low to run a Stamp system. You have to read the battery data sheet and graphs. If they claim 600mA-hour, you better expect more like 500mA-hour.
Another thing is that your system may not draw constant current. If so, you have to figure out an average current for each component that varies like that, and use the average in the math to find hours.
@Sylvie, A directional high gain antenna on the ground might help a lot, but I'm not aware of any made specifically for the XBee. I know they (Digi/Maxstream) do have high gain antennas available for the Xtend radios.
Tracy Allen said...
@Sylvie, A directional high gain antenna on the ground might help a lot, but I'm not aware of any made specifically for the XBee. I know they (Digi/Maxstream) do have high gain antennas available for the Xtend radios.
I don't want to hijack the thread here, so a quick response, and then maybe I'll start another one under "Completed Projects" if I want to add more beyond this quick response:
I see you're right. Here is Digi's list of antenna products:
There are dipoles available for the 2.4GHz XBees, but the only directional antennas (as I understand this) are for the 900MHz versions, or for the other Digi products (XStream, XTend, etc.).
Still, if I'm getting good data like I did Saturday with nothing but the 2.4GHz model and a tiny wire antenna on both ends, I can probably get all the range I'll ever need with a 900MHz and a dipole on each end. Maybe even with just the wire antenna on the transmitter (rocket mounted) side.
We did use higher gain dipoles with XTend modules on the high altitude balloon launch project I worked on a month ago, and easily received good data from 43 miles away (granted,·having a·transmitter that was 94,000 feet in the air must have helped considerably).
The directional antennas for 2.4 gHz at the bottom of the page are "special order" (ouch!) But right--Just try the pro and see. You could drive it up to your local hilltop on a pole, and then see how far it can get line of sight. A lot too has to do with local signal to noise conditions.
Sean, I should ask too if you have a meter available that will measure current? That is really a good test and a check on assumptions. Just measure the current by putting your ammeter in series with the battery that supplies the BOE. Do you know how to hook up a multimeter to measure milliamps?
·· Congrats on a successful flight and on successful data acquisition! You set up a wireless downlink for the data feed, yes?
"I set up the receiving station about 125 feet from the launchpad. It worked perfectly, with a nice flow of data through the entire flight... The data stopped nicely right after landing."
Can you post the raw data and/or a graph of the flight data? Where will you go from here?
Sorry I've been out of the loop, but I'm just back from New Hampshire ---> Washington ---> Marshall SFC, Alabama ---> Kennedy SFC ---> Marshall SFC ---> Washington ---> and then back to New Hampshire... with a fast drive from the airport for graduation. It was informative and exhausting, and now we can get back to work on our project!
Today we'll connect the two MAWD wires to the BOE, put the MAWD in a vacuum chamber,·then·run Tracy's initial program to confirm that the system is operational. Then we'll start editing·"last year's·program" (minus the servo ands Morse code commands, Tracy.) As I indicated before, our ultimate goal is to get the MAWD to output altitude data to the Datalogger at the same time it records temperature and humidity so we can correlate them. But I feel like we're light years behind you right now.
Other engineering insights·that have·surfaced (thanks to NASA educators and engineers)·include: 1) Very low temperatures·(-100 C) above 30,000 feet = decreased battery power?; 2) Low or no air density at high altitude means the parachute may not open until it·descends into more dense air (f = m x a), so the 'Pod' may be descending fast when the 'chute opens. This could cause a catastrophic parachute-Pod separation and all the parts could simple crash at high speed--- which is a good reason to use real-time data transfer (not possible for us due to limited time and budget): 3) The suggestion of a "cushion" of some sort on the bottom of the Pod (a crumple zone, an air-filled rubber bladder, etc.)
So off we go. Any suggestions on where to pick up? Where will you go from here, Sylvie? Nice work!! Let me know if I can help with your article; I'm an excellent proofreader and a technical editor.
Mr. Allen, Personally, no I do not have a meter that will measure current, but I’m not sure if Mr. Kibler has one. Also, no I don’t know how to hook up a multimeter to measure milliamps. Can you please explain how? Thank you all for your time and help, Sean from ARLISS-NH
We do have two volt meters and you are welcome to borrow one of them. They measure voltage, amperage, continuity, etc. Any ideas about what altitude we're aiming for...? Also, would you connect with Thomas and, between the two·of you, e-mail Mr.Biba and ask him for either:
1) A "RockSim file" of the rocket·our payload will go in; or
2) A very close approximation of the rocket's launch weight.
From these, and based on our payload weight, we will be able to predict various possible altitudes ondifferent rocket motors (10,000 feet? 30,000? what altitude are we aiming for,and why?)
Did you see that Sylvie succeeded in getting the BOE to read data from the MAWD, then send it from his rocket to the ground as the rocket descended?~! Great teamwork.
···· Our BOE-MAWD apparatus works! Attached are two graphs from the test I just did. I put MAWD altimeter in a vacuum chamber and evacuated the air (apparently to the same air density as 5,000 feet above ground level, which is the altitude the BOE read out.) Then I cut and pasted the raw data to Microsoft Excel, and bingo! We have graphs.
I did the first test on a bare BOE board and the second test on the ASP using Tracy's first program(attached.) Sylvie, I ran the brown wire to Vss and the blue wire (with a resistor) to I/O 5·like you suggested. I changed the I/O to 15 in·Tracy's·program when I used the ASP (since 5 was in use.)
Sylvie, did you use just the MAWD-BOE in your test flight? You mentioned the XBee-Pro but I'm not sure where that fits in. Where did you record your flight data (altitude); on an on-board BOE-MAWD? How did your test flights go?
Tracy, what's the next step·to program the BOE to read altitude/data from·the MAWD·and write·it to the Datalogger at the same time it's recording temperature and humidity data? You·said:
·Making any changes in a working setup is a big deal and you should weigh the pros and cons. I'm more inclined to suggest that you stick with what you've got.
Do you suggest we use a·BS2pe or BS2px, or stick with the BS2-ASP as it's currently wired and just tweak the program (which is my inclination.) On the ASP (BOE) there's room·at I/O 15 and on the Vss for the two MAWD wires.
My wife and son just headed off to Maine to our summer home. Thank you!! Now I can focus, uninterrupted. on "The Project" (as they call it.) As they drove off into the sunset (rain, actually) they said, "But when will we see you...?" I just smiled.
I attached the same graph twice. Attached is the "second" graph.
Tracy and Sylvie,
·· All things (and input) considered, I think it's probably better if we simply use the current BOE-Datalogger set-up (the ASP/robot hardware and program, minus servo and Morse code commands) since it's already wired, programmed, and operational. Since the kids are fairly familiar with the hardware and the software,·connecting two MAWD wires to available I/O·and Vss slots would be within their 'expertise' and their comfort zone. Given our time constraints (4 more, 3-hour meetings) using·the current·set-up seems both sage, and sane. It's the next progression in the evolution of a higher-order project and it will allow the Rocketeers·to use what they've already learned, then build from it (keeping in mind that we have some 'newbies' with us this time around.) I'd like to move ahead and learn how to get the Datalogger to read, record, and correlate the MAWD altitude data with the SHT temoerature and humidity data. What are your thoughts and suggestions?
Mark in NH said...
Tracy and Sylvie and ARLISS Rocketeers,
···· Our BOE-MAWD apparatus works! Attached are two graphs from the test I just did. I put MAWD altimeter in a vacuum chamber and evacuated the air (apparently to the same air density as 5,000 feet above ground level, which is the altitude the BOE read out.) Then I cut and pasted the raw data to Microsoft Excel, and bingo! We have graphs.
I did the first test on a bare BOE board and the second test on the ASP using Tracy's first program(attached.) Sylvie, I ran the brown wire to Vss and the blue wire (with a resistor) to I/O 5·like you suggested. I changed the I/O to 15 in·Tracy's·program when I used the ASP (since 5 was in use.)
Sylvie, did you use just the MAWD-BOE in your test flight? You mentioned the XBee-Pro but I'm not sure where that fits in. Where did you record your flight data (altitude); on an on-board BOE-MAWD? How did your test flights go?
Excellent! I'm thrilled to hear that you got it working. Exciting, isn't it? I don't know of anyone who is·reading the telemetry output from the MAWD (and I know a LOT of rocketeers), so we're on the cutting edge here.
On my flight I did not put any Stamps (BOE or otherwise) into the rocket. I sent the data from the MAWD straight to the XBee, which took those data and transmitted them to another XBee mounted on that Super Carrier Board (essentially a BOE) on the ground. The data recording happened on the ground, after the BS2px sent the data into an Excel spreadsheet on my laptop. I understand that's not how you're doing it - that's fine, of course.
I agree with your decision to stick with what you already know how to do as far as the datalogger. It's always best to stand on the shoulders of giants, even when the giant whose shoulders you're standing on is yourself. (isn't that quite the image?) I know well the issue of time constraints - it's extremely hard to schedule students' time, isn't it? I think they're busier than we are, sometimes.
I did make only one test flight so far. We have another launch in a few weeks, and I may try to fly again on that date, to a higher altitude, and with dual deployment instead of motor deployment. Yesterday morning I ground tested the setup with e-matches attached, to see if the XBee interferes with the MAWD's ability to fire ejection charges. It does not - dual deployment should work fine.
This morning I wrote and submitted an article on MAWD telemetry for Sport Rocketry magazine (the official magazine of the NAR). I haven't heard anything back yet. I'll keep you all informed about how that goes.
The shoulders of the giants we're standing on are yours and Tracy's! Thanks so much for your help; it's doubtful I would have figured out how to connect the MAWD to the BOE in the limited time we have, with the (hectic) schedule we have.
Yes, the kids' schedules are nearly as demanding as ours. I have to chuckle because two of·our·older Rocketeers are at a prep school Advanced Study Program for 5 weeks right now. The acronym, A.S.P., is the same as our Air Sampling Probe, the ASP. Fortunately they're allowed to go off-campus on Sundays for rocketry team practices (and they should be following and posting to the forum, right Mollie and Tyler?) Another 8th-grade Rocketeer, Andrew·goes to a (different) on-campus·program just as the first two finish. He received a substantial ($7,500) scholarship so he could attend, in large part because of his involvement with the rocketry and robotics programs (or so they say. I think he's simply a very talented kid!)
So any idea where we go with the programming at this point? At one level it's simple: just connect the two MWAD wires to the BOE. But then·the programming·gets really complicated because it has to interface with the current program and hardware. In theory I have an idea what to do next: "just" program I/O 15 (or whichever input we use) to receive the data from the MAWD. But where do I begin? The MAWD is sending data to the BOE faster than the 1-second read-record time on the Datalogger (one sample/second), which creates·a second, deeper·programming challenge. I'm sure we could eventually sort it out by trial-and-error programming; that's the long way·around. But we're beyond the basics (pun intended) of programming detailed in the Parallax books, and I don't understand the inuendo or programming at the deeper level-- how sub-routines interact with other sub-routines to make;·more advanced·commands, etc. We're in deep, fast-running water,·and any hints or advice would be much appreciated.
Finally, "mission patches" are being made, with the help of friends at NASA. Check out the attachment, and smile. Yours and Tracy's mission patches will be coming to you as soon as we get them. It seems like we're always fortunate to be surrounded by helpful friends. Kids, learn from this: be a friend and surround yourself with good people.·(*PS - Can·we all get autographed copies of 'Sport Rocketry' magazine when your article is published? Should we call you "Mr. Cutting Edge", or "Homer Hickam"...?!)
I definitely think you should evolve your current setup with the Stamp and BOE rather than making big changes in the platform or flavor of Stamp.
The program alterations to include the MAWD should not be too hard. We'll just have to synchronize the main program loop to the data as it is emitted by the MAWD. The "main" program loop will execute once each time it receives data from the MAWD. Or maybe every other time.
The first step will be to pare out the servo and Morse code functions from last year's final program and to be sure it still compiles and works without them. Those functions are quite independent, so it will take only a short time to have that done and tested.
Finally, "mission patches" are being made, with the help of friends at NASA. Check out the attachment, and smile. Yours and Tracy's mission patches will be coming to you as soon as we get them. It seems like we're always fortunate to be surrounded by helpful friends. Kids, learn from this: be a friend and surround yourself with good people.·(*PS - Can·we all get autographed copies of 'Sport Rocketry' magazine when your article is published? Should we call you "Mr. Cutting Edge", or "Homer Hickam"...?!)
Now that's extremely cool. Thanks.
Oh, you can call me "Doctor Smith". Or on second thought, how about just "Paul"?
I'll run copies of the article IF it gets published, and send it around to any of you who want it. Sport Rocketry is available to non-NAR members at magazine-intensive hobby shops - you might think about putting together an article about your group as well.
Re. the programming, that's Tracy's department, mostly. I learned a lot about that datalogger from last year's thread. You're getting great help from him, but don't underestimate the value to the rest of us of your having asked those questions in the first place.
As for the electronics side, don't be too impressed by the stuff I did, either. About two years ago I was happy to make LEDs blink with my little "What's a Microprocessor?" kit. I'm an educational psychologist, not an electrical engineer. But Parallax makes it easy to learn to do things like read the serial output of an altimeter and work with it like this. Surrounding yourself with good people is important, but so is picking a company that knows the value of good documentation.
·· The 'robot' program is being pared down as we "speak"-- the servomotor and Morse code commands are being edited out and we'll upload the revised program as soon as it's done. I may experiment to see if I can get the MAWD to read to the Datalogger. Two Rocketeers and I, in three different locations, are working on it through e-mail, and text messages. They seem to have a fairly good grasp about what to cull and what to leave, which means they've learned something valuable.
It was exciting when we got the MAWD hooked up to the BOE today and it churned out altitude data. "That's one small step for man..." and, at the same time,·a giant leap. I think we're not so far from where we want to be. We still have lots of physical engineering to do though: shorten the platform the BOE and MAWD mount on so there's room for the parachute, solder·new wires (for the dead-man pull) to the BOE, drill and mount the female connector to the ASP platform, drop test a 2 kg weight to make sure the parachute is large enough, mount the (as yet undefined) battery supplies, install a back-up shortwave transmitter, etc. It's·fun doing the·physical engineering; that's my forte. Figuring out the programming is a different kind of fun. I just wish we had more time! *Did you see·our team·mission patch (attached above?)
It's exciting too, that Sylvie is writing an article about "the gizmo" for 'Sport Rocketry' magazine.·What a team!
·· Attached is the updated·MAWDBOE_July01.BS2 program (the reconfigured 'robot program'.) The servomotor and Morse code commands for the movements are commented out, but not deleted. A few GOSUB commands were also commented out;·we·noted·these with·comments on their respective·lines.·We·also took out the IF MINUTE = $01 line so·the·program intiializes (?) IF INDEX > 02. It seemd to work though I'm not sure why...
Sync tries typically = 2 and disk tries typically = 1, though·they did vary as we commented out different line commands.·We kept the Morse code / LED for the number of sync tries so we have a visual verification; this can always be deleted later.
The program seems like it·should record data indefinitely now (though·we only let it run for 5 minutes. Maybe·we should leave it run all night...!) What can·we do to help at this point? Where do we go from here?
As I drifted off to sleep last night it occured to me:
1) If we use·a dead-man pull pin to activate the BOE at apogee, the·MAWD willl already be transmitting data since it activates when the rocket takes off.
2) If the BOE is switched on prior to liftoff, it will already be recording data when the MAWD starts transmitting data at liftoff.
3) It seems like either way, one of the two will be up and running when the other one initiates.
Neither of those should present any problems. You'll want to test it, of course, but you should be able to turn on the BOE while the MAWD is transmitting data, and pick up the data as soon as the BOE is "online". Alternatively, I already was turning the Stamp on before having the MAWD send data when I tested it here at home, and that worked just fine. There's no reason that I can see why they need to be started simultaneously, and in fact it'd be almost impossible to do so.
@Sean,
Here is a diagram of how to hook up the multimeter to measure current. The meter will be set to the position that measures milliamps, and you may have to move the probes to a different position than you use for measuring Volts or Ohms. Meters vary. Watch the meter as your program is running, and when the USB disk is writing data. Is that clear enough? Let us know what you find!
lol, Mark, when you said NASA patch, I at first thought you were talking about a "patch" for someone's software or hardware. Like, a bug fix, or duct tape. The real patch is very nice, points to the sky, but the grownups get to stay comfortably back on earth!
I am wondering if Sylvie or Mark can check with a stopwatch or some other means that there are in fact about 20 readings per second from the MAWD. Here is a program modified with an index to appear next to each reading, so if there are indeed 20 per second, it should count up to 200 in 10 seconds. There is a possibility that the extra code will make it miss every other reading. That would be of interest too.
1 millisecond to receive the MAWD data
49 milliseconds to do stuff before the next MAWD data
OR say we capture and log every 100th reading from MAWD, say, and that gives 5 seconds to read the RTC, the RH/temp and to write the data to the USB drive.
' {$BS2}
' {$PBASIC 2.5}
array VAR Byte(7)
ticks VAR Word
DO
ticks=ticks+1 // 10000 ' counts 0-9999
SERIN 5,84,40,escape,[noparse][[/noparse]STR array/7]
IF array(6)=LF THEN DEBUG DEC4 ticks,TAB,STR array\7 ' LF in array(6) means good data.
escape:
LOOP
The 'patch' isn't a NASA program patch (we're not quite ready for NASA yet). It's·our official ASP Payload Team Patch, made with help from our friends at NASA! The final version includes a blue and white 'Earth' icon just above the word 'A.S.P.' Cool beans, huh?!
I ran the MAWD for as close to 10 seconds as I could and the data count was 196... very close to the predicted 200. The raw data is attached as a file. In the first column the count started at 0324 and stopped at 0520. The second column has corresponding pressure altitude data.
I tweaked this line command slightly so it would run: SERIN·5,84,40,escape,[noparse][[/noparse]STR·array/7]
SERIN 5 was changed to 15 (one of the few open I/O's on the ASP-BOE)
[noparse][[/noparse]STR array/7] was changed to array\7
It seems that the MAWD outputs data at 20 data points a second. Yes?
My MAWD setup is no longer where I can easily attach it directly to a Stamp I/O pin, but I did run exactly that test a few times, and got close to 200 readings in 10 seconds. I wouldn't swear I was getting exactly 20/second, but it was definitely in the ballpark, as Mark just confirmed.
I do have some funny readings from the XBee-connected one that I flew: it looks like I got four consecutive identical readings each time the data were dumped into Excel. When I have a day to work on this (perhaps tomorrow) I'm going to transfer the ground station part to a Propeller chip (Propstick), in hopes that the much faster processor clears up that issue. I'm hoping that a Propellor will also be fast enough to drive an LCD to display the altitude in real time and the max altitude at the same time that it dumps the data into Excel.
·That's strange that you got four identical readings when you dumped the dat into Excel... could it have been a cut-and-paste error? Why would the XBee do that? It'd be cool to havconenct an LCD display that shows the altitude in real time, and the max altitude at the same time that it dumps data into Excel. That seems tricky. And you say it's only been 2 years since you first picked up·a Parallax programming book and started? I'm impressed. You must be a quick study.
Is it Paul Sylvie, or Paul Smith (or Mr. Cutting Edge)? How would you like your name to read on the mission patch --->·'Sylvie'?· It's not too late to change the proof, and it's no big thing. Really. We like·to keep all the campers·happy.
I fiddled and diddled around, cutting and pasting Tracy's MAWD program into the program we started with last year, thinking·I might miraculously get the MAWD altitude data onto the Datalogger/ flash drive.. It didn't work' so much for miracles (it didn't even TRY to work. Nary a byte.) It guess it's·time to read the book again.
PS - Check out the new TARC rules for next year's competition: the target altitude is 825 feet, but recovery is by STREAMER, not by parachute. I smell scrambled eggs for breakfast!
Mark
·That's strange that you got four identical readings when you dumped the dat into Excel... could it have been a cut-and-paste error? Why would the XBee do that? It'd be cool to havconenct an LCD display that shows the altitude in real time, and the max altitude at the same time that it dumps data into Excel. That seems tricky. And you say it's only been 2 years since you first picked up·a Parallax programming book and started? I'm impressed. You must be a quick study.
Is it Paul Sylvie, or Paul Smith (or Mr. Cutting Edge)? How would you like your name to read on the mission patch --->·'Sylvie'?· It's not too late to change the proof, and it's no big thing. Really. We like·to keep all the campers·happy.
I fiddled and diddled around, cutting and pasting Tracy's MAWD program into the program we started with last year, thinking·I might miraculously get the MAWD altitude data onto the Datalogger/ flash drive.. It didn't work' so much for miracles (it didn't even TRY to work. Nary a byte.) It guess it's·time to read the book again.
PS - Check out the new TARC rules for next year's competition: the target altitude is 825 feet, but recovery is by STREAMER, not by parachute. I smell scrambled eggs for breakfast!
Mark
It's "Paul Smith", and I guess I would prefer to be "Smith" rather than "Sylvie" on the patch, if you don't mind.
Sylvie is my cat, by the way. Way back the first time I ever registered for a web forum, it asked for a user name, and that's what popped into my head, and I've stuck with it ever since. I used to sign every post "From a guy, despite the username", but I got sick of doing it, and it doesn't seem to cause problems.
The data were dumped automatically from the BS2px into Excel through PLX-DAQ. I suspect it's some kind of timing thing. I'll see how things go with a Propeller supplying the data. They can easily handle 9600 baud.
I've only been messing with microprocessors for 2 years, though I did play with basic circuits a little before that. But again, don't be too impressed: with how easy they're making things these days, you can learn to do this kind of stuff in that kind of time, easy.
It should be straightforward to put MAWD altitudes that you've already read onto the datalogger, if you already know how to put data onto the logger. It's just another variable. But getting the timing right so that you're not losing several readings while doing that is going to be a challenge - one that Tracy will surely figure out for you.
We haven't had a TARC team to work with here in a few years, but we're priming the pump, as it were, with a very good private school in the area - the same one that had a team that introduced me to Parallax products about four years ago (for continuity's sake: yes, I bought the "What's a Microprocessor?" kit about two years before I really started playing with it. I was dept. chair at the time, so time was an issue).
Have a great time in Maine. My wife and I are heading down the coast for the weekend. A small town parade in Half Moon Bay, and then at night maybe to see the highly unofficial and tenuously illegal fireworks displays individuals shoot off on many of the small beaches in Santa Cruz. Some of these people have serious skyrockets. Fun, close up, and slightly dangerous, like old times.
I'm sure I'll have suggestions for the program when you return. I dug out the parts so that I can have a matching system (and a MAWD simulator). I want to check things before I suggest them. I don't think foresee any big problem with recording the data. It will not be possible to capture every MAWD reading, but enough for a good analysis of altitude and rate of descent.
The patch looks great!
Arrive a couple of weeks earlier at the Black Rock Desert and you can catch Burning Man!
Mr. Allen, · Thank you for the diagram it should help a lot. I'll be sure to let all of you know my results. I think I'll try and do it at Mr. Kibler's house during practice seeing how he has two meters that will measure current. If I have any questions, I will be sure to ask you. · Thank you all for your time and help, · · Sean from ARLISS-NH
Comments
Do you know how to estimate the battery life for your project?
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Tracy Allen
www.emesystems.com
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Tracy Allen
www.emesystems.com
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I don't think·I·know how to estimate the battery life for our project. How do you estimate the battery life? Does the Ultralife battery·last longer than the normal lithium batteries? Do they make rechargeable lithium or Ultralife batteries?
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Appreciate all your time and help,
·
Sean from ARLISS-NH
This opens up a LOT of possibilities. It'd be easy to make a version that sent down data from various sensors rather than from the MAWD. It'd be pretty easy to have control in the other direction as well - to send signals from the ground up to the rocket.
I'm going to try to hitch a ride on someone else's larger rocket in a few weeks, and fly the thing higher, to 3000 feet or so, to better test the range. I was probably about 2000-2500 feet from the rocket at the furthest point (1600 feet up, some distance downrange), and I never did lose contact with it. Could I get a mile of range from a standard XBee Pro, when it's way up in the air above me? We'll find out.
I don't think it'll work on a rocket going to 10K or 15K feet, though, but one of the 900MHz versions might, and one with a special antenna on at least one end (receiver or transmitter) very likely would.
total mA
= 2 milliamps for the Stamp
+ ? mA for power LED on the BOE
+ ? mA for the Sensirion
+ ? mA for the USB datalogger
+ ? mA internal for the 5 volt regulator
+ ? ...
Then you divide the battery capacity from its data sheet by the total current. Battery capacity in mA-hours, divided by mA, comes out with hours.
Actually, it is not quite that simple. There are a couple of things.
You have to be conservative about the battery capacity, particularly if there is anything on board that draws a lot of current. When battery companies tell you the capacity, it is to a voltage level and with a certain current drain, and it is usually a voltage level too low to run a Stamp system. You have to read the battery data sheet and graphs. If they claim 600mA-hour, you better expect more like 500mA-hour.
Another thing is that your system may not draw constant current. If so, you have to figure out an average current for each component that varies like that, and use the average in the math to find hours.
@Sylvie, A directional high gain antenna on the ground might help a lot, but I'm not aware of any made specifically for the XBee. I know they (Digi/Maxstream) do have high gain antennas available for the Xtend radios.
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Tracy Allen
www.emesystems.com
I see you're right. Here is Digi's list of antenna products:
http://www.digi.com/products/accessories/antennas/whip-antennas.jsp
There are dipoles available for the 2.4GHz XBees, but the only directional antennas (as I understand this) are for the 900MHz versions, or for the other Digi products (XStream, XTend, etc.).
Still, if I'm getting good data like I did Saturday with nothing but the 2.4GHz model and a tiny wire antenna on both ends, I can probably get all the range I'll ever need with a 900MHz and a dipole on each end. Maybe even with just the wire antenna on the transmitter (rocket mounted) side.
We did use higher gain dipoles with XTend modules on the high altitude balloon launch project I worked on a month ago, and easily received good data from 43 miles away (granted,·having a·transmitter that was 94,000 feet in the air must have helped considerably).
Sean, I should ask too if you have a meter available that will measure current? That is really a good test and a check on assumptions. Just measure the current by putting your ammeter in series with the battery that supplies the BOE. Do you know how to hook up a multimeter to measure milliamps?
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Tracy Allen
www.emesystems.com
·· Congrats on a successful flight and on successful data acquisition! You set up a wireless downlink for the data feed, yes?
"I set up the receiving station about 125 feet from the launchpad. It worked perfectly, with a nice flow of data through the entire flight... The data stopped nicely right after landing."
Can you post the raw data and/or a graph of the flight data? Where will you go from here?
Sorry I've been out of the loop, but I'm just back from New Hampshire ---> Washington ---> Marshall SFC, Alabama ---> Kennedy SFC ---> Marshall SFC ---> Washington ---> and then back to New Hampshire... with a fast drive from the airport for graduation. It was informative and exhausting, and now we can get back to work on our project!
Today we'll connect the two MAWD wires to the BOE, put the MAWD in a vacuum chamber,·then·run Tracy's initial program to confirm that the system is operational. Then we'll start editing·"last year's·program" (minus the servo ands Morse code commands, Tracy.) As I indicated before, our ultimate goal is to get the MAWD to output altitude data to the Datalogger at the same time it records temperature and humidity so we can correlate them. But I feel like we're light years behind you right now.
Other engineering insights·that have·surfaced (thanks to NASA educators and engineers)·include: 1) Very low temperatures·(-100 C) above 30,000 feet = decreased battery power?; 2) Low or no air density at high altitude means the parachute may not open until it·descends into more dense air (f = m x a), so the 'Pod' may be descending fast when the 'chute opens. This could cause a catastrophic parachute-Pod separation and all the parts could simple crash at high speed--- which is a good reason to use real-time data transfer (not possible for us due to limited time and budget): 3) The suggestion of a "cushion" of some sort on the bottom of the Pod (a crumple zone, an air-filled rubber bladder, etc.)
So off we go. Any suggestions on where to pick up? Where will you go from here, Sylvie? Nice work!! Let me know if I can help with your article; I'm an excellent proofreader and a technical editor.
Cheers!
Mark
Personally, no I do not have a meter that will measure current, but I’m not sure if Mr. Kibler has one. Also, no I don’t know how to hook up a multimeter to measure milliamps. Can you please explain how?
Thank you all for your time and help,
Sean from ARLISS-NH
We do have two volt meters and you are welcome to borrow one of them. They measure voltage, amperage, continuity, etc. Any ideas about what altitude we're aiming for...? Also, would you connect with Thomas and, between the two·of you, e-mail Mr.Biba and ask him for either:
1) A "RockSim file" of the rocket·our payload will go in; or
2) A very close approximation of the rocket's launch weight.
From these, and based on our payload weight, we will be able to predict various possible altitudes ondifferent rocket motors (10,000 feet? 30,000? what altitude are we aiming for,and why?)
Did you see that Sylvie succeeded in getting the BOE to read data from the MAWD, then send it from his rocket to the ground as the rocket descended?~! Great teamwork.
Mr. Kibler
···· Our BOE-MAWD apparatus works! Attached are two graphs from the test I just did. I put MAWD altimeter in a vacuum chamber and evacuated the air (apparently to the same air density as 5,000 feet above ground level, which is the altitude the BOE read out.) Then I cut and pasted the raw data to Microsoft Excel, and bingo! We have graphs.
I did the first test on a bare BOE board and the second test on the ASP using Tracy's first program(attached.) Sylvie, I ran the brown wire to Vss and the blue wire (with a resistor) to I/O 5·like you suggested. I changed the I/O to 15 in·Tracy's·program when I used the ASP (since 5 was in use.)
Sylvie, did you use just the MAWD-BOE in your test flight? You mentioned the XBee-Pro but I'm not sure where that fits in. Where did you record your flight data (altitude); on an on-board BOE-MAWD? How did your test flights go?
Tracy, what's the next step·to program the BOE to read altitude/data from·the MAWD·and write·it to the Datalogger at the same time it's recording temperature and humidity data? You·said:
·Making any changes in a working setup is a big deal and you should weigh the pros and cons. I'm more inclined to suggest that you stick with what you've got.
Do you suggest we use a·BS2pe or BS2px, or stick with the BS2-ASP as it's currently wired and just tweak the program (which is my inclination.) On the ASP (BOE) there's room·at I/O 15 and on the Vss for the two MAWD wires.
My wife and son just headed off to Maine to our summer home. Thank you!! Now I can focus, uninterrupted. on "The Project" (as they call it.) As they drove off into the sunset (rain, actually) they said, "But when will we see you...?" I just smiled.
Success!
Mark
I attached the same graph twice. Attached is the "second" graph.
Tracy and Sylvie,
·· All things (and input) considered, I think it's probably better if we simply use the current BOE-Datalogger set-up (the ASP/robot hardware and program, minus servo and Morse code commands) since it's already wired, programmed, and operational. Since the kids are fairly familiar with the hardware and the software,·connecting two MAWD wires to available I/O·and Vss slots would be within their 'expertise' and their comfort zone. Given our time constraints (4 more, 3-hour meetings) using·the current·set-up seems both sage, and sane. It's the next progression in the evolution of a higher-order project and it will allow the Rocketeers·to use what they've already learned, then build from it (keeping in mind that we have some 'newbies' with us this time around.) I'd like to move ahead and learn how to get the Datalogger to read, record, and correlate the MAWD altitude data with the SHT temoerature and humidity data. What are your thoughts and suggestions?
Warm regards,
Mark
On my flight I did not put any Stamps (BOE or otherwise) into the rocket. I sent the data from the MAWD straight to the XBee, which took those data and transmitted them to another XBee mounted on that Super Carrier Board (essentially a BOE) on the ground. The data recording happened on the ground, after the BS2px sent the data into an Excel spreadsheet on my laptop. I understand that's not how you're doing it - that's fine, of course.
I agree with your decision to stick with what you already know how to do as far as the datalogger. It's always best to stand on the shoulders of giants, even when the giant whose shoulders you're standing on is yourself. (isn't that quite the image?) I know well the issue of time constraints - it's extremely hard to schedule students' time, isn't it? I think they're busier than we are, sometimes.
I did make only one test flight so far. We have another launch in a few weeks, and I may try to fly again on that date, to a higher altitude, and with dual deployment instead of motor deployment. Yesterday morning I ground tested the setup with e-matches attached, to see if the XBee interferes with the MAWD's ability to fire ejection charges. It does not - dual deployment should work fine.
This morning I wrote and submitted an article on MAWD telemetry for Sport Rocketry magazine (the official magazine of the NAR). I haven't heard anything back yet. I'll keep you all informed about how that goes.
The shoulders of the giants we're standing on are yours and Tracy's! Thanks so much for your help; it's doubtful I would have figured out how to connect the MAWD to the BOE in the limited time we have, with the (hectic) schedule we have.
Yes, the kids' schedules are nearly as demanding as ours. I have to chuckle because two of·our·older Rocketeers are at a prep school Advanced Study Program for 5 weeks right now. The acronym, A.S.P., is the same as our Air Sampling Probe, the ASP. Fortunately they're allowed to go off-campus on Sundays for rocketry team practices (and they should be following and posting to the forum, right Mollie and Tyler?) Another 8th-grade Rocketeer, Andrew·goes to a (different) on-campus·program just as the first two finish. He received a substantial ($7,500) scholarship so he could attend, in large part because of his involvement with the rocketry and robotics programs (or so they say. I think he's simply a very talented kid!)
So any idea where we go with the programming at this point? At one level it's simple: just connect the two MWAD wires to the BOE. But then·the programming·gets really complicated because it has to interface with the current program and hardware. In theory I have an idea what to do next: "just" program I/O 15 (or whichever input we use) to receive the data from the MAWD. But where do I begin? The MAWD is sending data to the BOE faster than the 1-second read-record time on the Datalogger (one sample/second), which creates·a second, deeper·programming challenge. I'm sure we could eventually sort it out by trial-and-error programming; that's the long way·around. But we're beyond the basics (pun intended) of programming detailed in the Parallax books, and I don't understand the inuendo or programming at the deeper level-- how sub-routines interact with other sub-routines to make;·more advanced·commands, etc. We're in deep, fast-running water,·and any hints or advice would be much appreciated.
Finally, "mission patches" are being made, with the help of friends at NASA. Check out the attachment, and smile. Yours and Tracy's mission patches will be coming to you as soon as we get them. It seems like we're always fortunate to be surrounded by helpful friends. Kids, learn from this: be a friend and surround yourself with good people.·(*PS - Can·we all get autographed copies of 'Sport Rocketry' magazine when your article is published? Should we call you "Mr. Cutting Edge", or "Homer Hickam"...?!)
Mark
I definitely think you should evolve your current setup with the Stamp and BOE rather than making big changes in the platform or flavor of Stamp.
The program alterations to include the MAWD should not be too hard. We'll just have to synchronize the main program loop to the data as it is emitted by the MAWD. The "main" program loop will execute once each time it receives data from the MAWD. Or maybe every other time.
The first step will be to pare out the servo and Morse code functions from last year's final program and to be sure it still compiles and works without them. Those functions are quite independent, so it will take only a short time to have that done and tested.
More after work. We are on West Coast time here!
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Tracy Allen
www.emesystems.com
Oh, you can call me "Doctor Smith". Or on second thought, how about just "Paul"?
I'll run copies of the article IF it gets published, and send it around to any of you who want it. Sport Rocketry is available to non-NAR members at magazine-intensive hobby shops - you might think about putting together an article about your group as well.
Re. the programming, that's Tracy's department, mostly. I learned a lot about that datalogger from last year's thread. You're getting great help from him, but don't underestimate the value to the rest of us of your having asked those questions in the first place.
As for the electronics side, don't be too impressed by the stuff I did, either. About two years ago I was happy to make LEDs blink with my little "What's a Microprocessor?" kit. I'm an educational psychologist, not an electrical engineer. But Parallax makes it easy to learn to do things like read the serial output of an altimeter and work with it like this. Surrounding yourself with good people is important, but so is picking a company that knows the value of good documentation.
·· The 'robot' program is being pared down as we "speak"-- the servomotor and Morse code commands are being edited out and we'll upload the revised program as soon as it's done. I may experiment to see if I can get the MAWD to read to the Datalogger. Two Rocketeers and I, in three different locations, are working on it through e-mail, and text messages. They seem to have a fairly good grasp about what to cull and what to leave, which means they've learned something valuable.
It was exciting when we got the MAWD hooked up to the BOE today and it churned out altitude data. "That's one small step for man..." and, at the same time,·a giant leap. I think we're not so far from where we want to be. We still have lots of physical engineering to do though: shorten the platform the BOE and MAWD mount on so there's room for the parachute, solder·new wires (for the dead-man pull) to the BOE, drill and mount the female connector to the ASP platform, drop test a 2 kg weight to make sure the parachute is large enough, mount the (as yet undefined) battery supplies, install a back-up shortwave transmitter, etc. It's·fun doing the·physical engineering; that's my forte. Figuring out the programming is a different kind of fun. I just wish we had more time! *Did you see·our team·mission patch (attached above?)
It's exciting too, that Sylvie is writing an article about "the gizmo" for 'Sport Rocketry' magazine.·What a team!
·· Attached is the updated·MAWDBOE_July01.BS2 program (the reconfigured 'robot program'.) The servomotor and Morse code commands for the movements are commented out, but not deleted. A few GOSUB commands were also commented out;·we·noted·these with·comments on their respective·lines.·We·also took out the IF MINUTE = $01 line so·the·program intiializes (?) IF INDEX > 02. It seemd to work though I'm not sure why...
Sync tries typically = 2 and disk tries typically = 1, though·they did vary as we commented out different line commands.·We kept the Morse code / LED for the number of sync tries so we have a visual verification; this can always be deleted later.
The program seems like it·should record data indefinitely now (though·we only let it run for 5 minutes. Maybe·we should leave it run all night...!) What can·we do to help at this point? Where do we go from here?
Mark
As I drifted off to sleep last night it occured to me:
1) If we use·a dead-man pull pin to activate the BOE at apogee, the·MAWD willl already be transmitting data since it activates when the rocket takes off.
2) If the BOE is switched on prior to liftoff, it will already be recording data when the MAWD starts transmitting data at liftoff.
3) It seems like either way, one of the two will be up and running when the other one initiates.
Hmmm,
Mark
Here is a diagram of how to hook up the multimeter to measure current. The meter will be set to the position that measures milliamps, and you may have to move the probes to a different position than you use for measuring Volts or Ohms. Meters vary. Watch the meter as your program is running, and when the USB disk is writing data. Is that clear enough? Let us know what you find!
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Tracy Allen
www.emesystems.com
I am wondering if Sylvie or Mark can check with a stopwatch or some other means that there are in fact about 20 readings per second from the MAWD. Here is a program modified with an index to appear next to each reading, so if there are indeed 20 per second, it should count up to 200 in 10 seconds. There is a possibility that the extra code will make it miss every other reading. That would be of interest too.
1 millisecond to receive the MAWD data
49 milliseconds to do stuff before the next MAWD data
OR say we capture and log every 100th reading from MAWD, say, and that gives 5 seconds to read the RTC, the RH/temp and to write the data to the USB drive.
' {$BS2} ' {$PBASIC 2.5} array VAR Byte(7) ticks VAR Word DO ticks=ticks+1 // 10000 ' counts 0-9999 SERIN 5,84,40,escape,[noparse][[/noparse]STR array/7] IF array(6)=LF THEN DEBUG DEC4 ticks,TAB,STR array\7 ' LF in array(6) means good data. escape: LOOP▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Tracy Allen
www.emesystems.com
The 'patch' isn't a NASA program patch (we're not quite ready for NASA yet). It's·our official ASP Payload Team Patch, made with help from our friends at NASA! The final version includes a blue and white 'Earth' icon just above the word 'A.S.P.' Cool beans, huh?!
I ran the MAWD for as close to 10 seconds as I could and the data count was 196... very close to the predicted 200. The raw data is attached as a file. In the first column the count started at 0324 and stopped at 0520. The second column has corresponding pressure altitude data.
I tweaked this line command slightly so it would run: SERIN·5,84,40,escape,[noparse][[/noparse]STR·array/7]
SERIN 5 was changed to 15 (one of the few open I/O's on the ASP-BOE)
[noparse][[/noparse]STR array/7] was changed to array\7
It seems that the MAWD outputs data at 20 data points a second. Yes?
Mark
I do have some funny readings from the XBee-connected one that I flew: it looks like I got four consecutive identical readings each time the data were dumped into Excel. When I have a day to work on this (perhaps tomorrow) I'm going to transfer the ground station part to a Propeller chip (Propstick), in hopes that the much faster processor clears up that issue. I'm hoping that a Propellor will also be fast enough to drive an LCD to display the altitude in real time and the max altitude at the same time that it dumps the data into Excel.
·That's strange that you got four identical readings when you dumped the dat into Excel... could it have been a cut-and-paste error? Why would the XBee do that? It'd be cool to havconenct an LCD display that shows the altitude in real time, and the max altitude at the same time that it dumps data into Excel. That seems tricky. And you say it's only been 2 years since you first picked up·a Parallax programming book and started? I'm impressed. You must be a quick study.
Is it Paul Sylvie, or Paul Smith (or Mr. Cutting Edge)? How would you like your name to read on the mission patch --->·'Sylvie'?· It's not too late to change the proof, and it's no big thing. Really. We like·to keep all the campers·happy.
I fiddled and diddled around, cutting and pasting Tracy's MAWD program into the program we started with last year, thinking·I might miraculously get the MAWD altitude data onto the Datalogger/ flash drive.. It didn't work' so much for miracles (it didn't even TRY to work. Nary a byte.) It guess it's·time to read the book again.
PS - Check out the new TARC rules for next year's competition: the target altitude is 825 feet, but recovery is by STREAMER, not by parachute. I smell scrambled eggs for breakfast!
Mark
·
Sylvie is my cat, by the way. Way back the first time I ever registered for a web forum, it asked for a user name, and that's what popped into my head, and I've stuck with it ever since. I used to sign every post "From a guy, despite the username", but I got sick of doing it, and it doesn't seem to cause problems.
The data were dumped automatically from the BS2px into Excel through PLX-DAQ. I suspect it's some kind of timing thing. I'll see how things go with a Propeller supplying the data. They can easily handle 9600 baud.
I've only been messing with microprocessors for 2 years, though I did play with basic circuits a little before that. But again, don't be too impressed: with how easy they're making things these days, you can learn to do this kind of stuff in that kind of time, easy.
It should be straightforward to put MAWD altitudes that you've already read onto the datalogger, if you already know how to put data onto the logger. It's just another variable. But getting the timing right so that you're not losing several readings while doing that is going to be a challenge - one that Tracy will surely figure out for you.
We haven't had a TARC team to work with here in a few years, but we're priming the pump, as it were, with a very good private school in the area - the same one that had a team that introduced me to Parallax products about four years ago (for continuity's sake: yes, I bought the "What's a Microprocessor?" kit about two years before I really started playing with it. I was dept. chair at the time, so time was an issue).
·· Off to Maine to catch up with the family for the holiday weekend. "See" you in a few days. I hope you have a pleasant holiday.
Attached is the updated mission patch. I think this is the final·edition unless anyone has any suggestions or revisions. OK?
Mark
I'm sure I'll have suggestions for the program when you return. I dug out the parts so that I can have a matching system (and a MAWD simulator). I want to check things before I suggest them. I don't think foresee any big problem with recording the data. It will not be possible to capture every MAWD reading, but enough for a good analysis of altitude and rate of descent.
The patch looks great!
Arrive a couple of weeks earlier at the Black Rock Desert and you can catch Burning Man!
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Tracy Allen
www.emesystems.com
·
Thank you for the diagram it should help a lot. I'll be sure to let all of you know my results. I think I'll try and do it at Mr. Kibler's house during practice seeing how he has two meters that will measure current. If I have any questions, I will be sure to ask you.
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Thank you all for your time and help,
·
·
Sean from ARLISS-NH