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Discussion in 'Rocketry Electronics and Software' started by azzie, Dec 23, 2014.
Also, Alex, your altimeter comparison spreadsheet doesn't appear include the AltusMetrum TeleMini.
anyone know what the smallest and cheapest altimeter you can use with smaller estes rockets?.I think the smallest is 10mm? thanks
Heres a repost for a good comparison website. http://rocketsetc.com/data/
I saw that before,but it didn't help much.
That list can be sorted by Fit the smallest are the PicoAlt PICO-P1 and the Adrel BMP, the first fits a 12mm tube (BT-5) and the second a 13mm tube, the prices have probably increased a bit from $40 and $55. There may be other newer ones that will fit small airframes but those are the smallest two listed.
ALT-BMP has shrunk : 7,9 x 19,3 x 4,9 mm (with connector); 0.6g not including battery.
It can fit in a 10mm -coupler-.
thank you sirs.
hmm,the pico website does not work.I get google error "server not connected". adrel is in poland.prices are in euros and shipping must be crazy high.those are out,lol.
iirc there is supposed to be a Adrel dealer in the US, someone on TRF mentioned it not long ago.
Adrel shipping took a while, but was not outrageous.
maybe jolly logic will come out with a smaller unit. I have the altimeter one.
I hear John is working on the JL4 and its pretty small.
Great job Alex.
Why hasn't someone logged the AltiDuo ($30 arduino altimiter with digital filtering). It's a great little unit that comes in kit or as a completed.
Three updates: first, the Altus Metrum microPeak's price was reduced to $30 for the unit itself some time ago. (http://shop.gag.com/altimeters/micropeak.html)
Second, the long-advertised external data display device for the PerfectFlite FireFly is now real and available. It provides a means to read apogee, peak speed, time to apogee, total flight time, descent rate, and battery voltage of both the display unit itself and the FireFly via an LCD display. Here's the display unit: http://www.perfectflitedirect.com/firefly-field-data-display/ I have one and it works actually quite nicely. Oddly, it's not yet on the regular PerfectFlite site. Maybe a notation over in the OS column for the FireFly would be where you'd mention this, since it's not essential to use the unit as a peak-reading altimeter. Or maybe an addition to the "Click!" notation in the "Record" column. Whatever works best for keeping things consistent.
Finally, the NAR has recently revised the list of altimeters accepted for competition use, and the list is much shorter than before. The current list is here: http://www.nar.org/contest-flying/u...appendix/altimeters-approved-for-contest-use/ So....some of the check marks to remove from the "competition" column.
One data point that might be worth adding - support for staged rockets - my emails to @John Bean last week confirmed that the Altimeter3 will likely not understand a multi staged rocket... Given he's on the thread, he might be able to expand...
I think the all time smallest baro dual deploy was the Pico unit but I suspect Robert Dehate is not selling them anymore. It will fit in just about any modroc but............ and I do mean but.............. Trying to get all the pieces into a small space is
challenging and a setup interface has to be cobbled together and is not easy to change. There are also several wiring schemes suggested that would be confusing to a neophyte. Kurt
Like AltimeterTwo, AltimeterThree expects one engine, so that's what it will report (and while some stats like apogee will be fine, otherslike max speedmay not). The second engine will be ignored, or in rare cases may fool the ejection detection and muck up some of the timing stats and the ejection altitude.
With a slight tweak to software, we could add "2 Stage Analysis." That would lengthen the list of stats shown in the app, and add a stat for interstage coast. Max speed would continue to be calculated and would presumably occur during second stage boost.
A stat for calculating Cd (decel * velocity^2) has also been requested.
consider this my formal RFE (Request For Enhancement)!!
I'm Rich and today is the first day I'm posting to the forums.
I'm interested in using off-the-shelf components to assemble flight instrumentation.
This past weekend I flew a Lance Delta with two (2) units to record the altitude profile; a RRC3 and a bme280 polled by a Raspberry Pi Zero.
The apogee readings agree to with approximately one (1) foot, at ~970 feet, the shape of the profile graphs also agree very well.
The big difference appears to be the RRC3 is recording data about twice as fast as the RPi.
I had the RPi programmed to poll the bme280 at 10/sec.
Next month I hope to fly a similar configuration to 3-4k feet.
Is anyone else experimenting with off-the-shelf components and specifically the bme280?
Indeed I am! (Arduino/BMP though, so no humidity)
Why the Pi, and why the RRC3? I use a PerfectFlite Firefly as my backup/calibration altimeter. If you're using it for deployment that makes a lot of sense but I wouldn't use it otherwise.
My altimeter read 7K on a 1k flight though... Probably a bad first sample. Be sure to get lots of readings at ground level...
Another neat technique I saw somewhere is to make each reading, say, 20% of the sensor value plus 80% of the previous reading. That way one jump in readings won't entirely mess it up.
Sent from my LGL44VL using Rocketry Forum mobile app
The RRC3 was on the shelf after my L1 and L2 dual deploy flights.
The RPi Zero because out-of-the-box I want on-board WiFi, wide choice of languages, console and graphics interfaces, FTP...
PS: Thanks for the tips!
That dealer is North Coast Rocketry and they do have current stock. Also some who sell NCR stuff (eRockets.biz, for example) have them. The price has gone up a bit relative to what’s in the comparison table though. It’s $65 for the unit and $87 for the “kit” (altimeter, battery, charger/computer interface device).
They also finally have a version of the interface software that doesn’t require Windows security feature workarounds. Right now one has to go to the Adrel site to get that: http://www.adrel.com.pl/download.html
The Eggtimer Proton is now on the Altimeter Comparison Guide, thanks Alex!
Bosch makes very high quality pressure sensors, and that's been mostly what Jolly Logic has used historically. They are digital and temperature-compensated (definite requirements these days), but you have to do a fair amount of math to turn the raw pressure and temperature output into temperature-compensated pressure, as you probably know by now. Other pressure sensors like those made by ST do all of that internally, rather than make you do it.
Whether you use Bosch parts or not, one tip is to convert all of your math to integer math rather than doing any floating point calculations (ever). No Jolly Logic products have ever used a floating point calculation on the altimeter (even when they show decimals on the screen). Floating point calcs are a huge waste of cycles and energy. Everything—even GPS coordinates—can be stored and calculated as integers, oftentimes MUCH more efficiently. Just a tip.
FYI, I updated altimeter comparison guide (added several new altimeters, removed altimeters that are no longer available, updated prices, etc).
Am I missing new altimeters? Let me know!
I was just looking at the Adrell ALT-BMP on their website. It states that "detection of takeoff" can be set for 2m - 100m.
Does that mean that you LOSE 2m of actual altitude ( minimum ) when the unit reports ?
Also, the unit measures 1 time per second . . . A second is a long time in a rocket !
No, it uses buffered altitude measurements as the starting value.
I don't know the use case for sampling at such low rate - And the lowest sampling rate is once every 2 seconds if you read the user guide. Though they recommend using the 15 Hz sampling rate in general. Maybe it has some use for the competition events like parachute duration?
That is a setting to choose how much altitude change the device needs to "see" before it's decided it's flying. This capability is not unique to the Adrel.
Some other altimeters also let you set that value (see, for example, Perfectflite Pnut). I have no idea what a 2m launch detect threshold might be good for as that also would make it really sensitive to things like breezes blowing by the static ports on your model or pressure changes as you button things up after you turn it on and the "delay" time has expired. (This delay is how long the unit waits before "looking" for a launch and is configurable on the Adrel even though this is not shown in Adrel's documentation - it is available in their interface application in the same panel as the launch detect height and sample rate settings.)
The sample rate choices would be for different applications. Look at the documentation for the Jolly Logic AltimeterThree to see some non-rocketry uses that might be OK with lower sample rates. NAR-accepted (and I think also FAI-accepted) competition rocketry altimeters much have sample rates of at least 10/second to be accepted, and as hartich noted, 15 samples/second is recommended by Adrel for rocket competition use.
Just noticed the reply on this relatively old query. Thanks for the tips.
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