The plan is for the XS to be $59 and the EZ, which includes battery and switch, to be $74. These are preliminary targets, since I don't have quotes yet for some of the costs.
Featherweight Sparrow Altimeter
- Thread starter Adrian A
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The plan is for the XS to be $59 and the EZ, which includes battery and switch, to be $74. These are preliminary targets, since I don't have quotes yet for some of the costs.
KenRico
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With a LOUD Beeper this may not be an issue...I am hungry for ease of use - if this fits in an Adrian recommended BlueTube coupler , the coupler can be glued in some unusual places like a 5" Jart Nosecone coupler or an existing bay but mounting this way would not require a sled or modify existing sled and would be completely isolated - just add a small vent hole and ready to rock.
I wanted to do something like that with the Raven3 and av bay kits I bought - but it is extremely hard to hear if armed when buttoned up .
Kenny
Both versions of the Sparrow are designed to be mounted to a conventional sled, though the built-in battery and switch of the EZ will make it simpler to mount in almost any location. The beeper is louder than the Raven's, but it's a piezo beeper at a higher pitch, so it might depend more on your high-frequency hearing. I have considered making another variant of the Sparrow with a Raven-style form factor that would plug into all the Fearherweight av-bays.
First I need to get these two variants tested and into production,, though.
Fdog
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Have you tried this?
It's what I do and it works like a charm. I'm not hard of hearing, and I had issues discerning between two Ravens beeping away in the AV bay. Folks will snicker at you, but who cares? It works so well I'm amazed that everyone doesn't auscultate their rockets!
All the best, James
KenRico
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Have you tried this?
It's what I do and it works like a charm. I'm not hard of hearing, and I had issues discerning between two Ravens beeping away in the AV bay. Folks will snicker at you, but who cares? It works so well I'm amazed that everyone doesn't auscultate their rockets!
All the best, James
You are DR ROCKET James !
Did not think of that, already have a FYRWRX continuity tester hanging around my neck at launch ... inexpensive stethoscope is not a stretch . Also can see it will be a definite conversation starter !
Kenny
Viperfixr
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I am liking that EZ for $74! Count me in.
Last night I reached a nice milestone: The first rev of the firmware is complete and all known bugs are gone. (Finally!)
I started to write up a detailed description of everything it does, but I think it's better to just start with what the user needs to know (a much shorter description):
You can set the main chute altitude in the field with a simple rotary switch, in 100 foot increments up to 1500 feet. The setting is always visible, whether or not it's powered on.
When you power it up, there is an immediate beep, followed by a beep-out of the battery voltage in 10ths of a volt.
From then until liftoff is detected it beeps out the continuity status of the 2 channels. A high, short beep and a green LED indicates the channel has continuity. A long, lower beep and a red LED flash indicates no continuity for that channel. The altimeter is ready for launch.
In flight, it fires the apogee and main chute channels reliably, every time, for any flight profile or maximum Mach number.
After landing, it periodically beeps out the altitude of the flight, in feet, until you turn it off.
The Sparrow also records lots of data for the most recent 5 flights. You can download the data to a computer if you want, or just keep flying the altimeter without ever hooking it up to a computer.
I started to write up a detailed description of everything it does, but I think it's better to just start with what the user needs to know (a much shorter description):
You can set the main chute altitude in the field with a simple rotary switch, in 100 foot increments up to 1500 feet. The setting is always visible, whether or not it's powered on.
When you power it up, there is an immediate beep, followed by a beep-out of the battery voltage in 10ths of a volt.
From then until liftoff is detected it beeps out the continuity status of the 2 channels. A high, short beep and a green LED indicates the channel has continuity. A long, lower beep and a red LED flash indicates no continuity for that channel. The altimeter is ready for launch.
In flight, it fires the apogee and main chute channels reliably, every time, for any flight profile or maximum Mach number.
After landing, it periodically beeps out the altitude of the flight, in feet, until you turn it off.
The Sparrow also records lots of data for the most recent 5 flights. You can download the data to a computer if you want, or just keep flying the altimeter without ever hooking it up to a computer.
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Now for the under-the-hood version, for those interested in the details:
Both versions of the Sparrow are mounted through two 4-40 size, grounded screw holes. No need to worry about insulating spacers or conductive sleds.
You can set the main chute altitude in the field with a simple rotary switch, in 100 foot increments up to 1500 feet. If you ever want to know what the main chute deployment altitude is set to, no need to power it on or look up jumper settings, just read the number indicated on the dial. The switch is a 16-position DIP switch labeled 0-9 then A-F. 1 is 100 feet, 9 is 900 feet, A is 1000 feet, F is 1500 feet, etc. I'm not yet sure what's the best use for the 0 setting; for now it will also just fire at 100 feet.
When you power it up, there is an immediate beep, followed by a beep-out of the battery voltage in 10ths of a volt.
Then it beeps out the continuity status of the 2 channels. A high beep and a green LED indicates the channel has continuity. A long, lower beep and a red LED flash indicates no continuity for that channel. (Just like the Raven, but with 2 channels instead of 4, and with color-coded LEDs for clarity) The altimeter is ready for launch. The altimeter uses a piezo buzzer that consumes much, much less power than the one used on the Raven, significantly improving the battery life. I'm not sure yet how long it can hang out at the pad with the smallest batteries, but it will be many hours.
The pad altitude is updated continuously, with enough time lag so that even a very slow launch won't be mistaken for a change in pad altitude. The altitude used for liftoff detection is filtered so that a transient from the rocket being dropped, etc. won't be mistaken for liftoff. Several seconds of data is continuously buffered so that all of the flight is recorded, even for a slow liftoff that delays the liftoff detection.
After liftoff, the altimeter records at 20 Hz the raw baro pressure in 1/25000 of an atm, temperature with 0.2F resolution, battery voltage, apogee channel voltage, and main chute voltage with 15 mV resolution. Also recorded is a digital flight events register that includes all of the flight event states that are used for deployment decisions (liftoff detection, velocity check status, apogee detection, altitude < main chute setpoint, and which channels fired). Velocity and other derived measurements that are calculated for use on board and can be reconstructed after the flight are omitted from the recording to maximize space. The Sparrow also records the pad altitude and flight number (odometer reading) in a 1-time slot at the start of the flight.
During the flight, the altimeter uses a combination of filters so than any spurious barometric data spikes are thrown out, and then the validated data is smoothed from there. Velocity is calculated and smoothed again before it is used, so that it's reliable for the deployment logic. Both channels are set to check that the vertical velocity is well under the level at which Mach effects can affect the data, for at least 2 seconds. When the rocket starts to descend, the apogee charge fires for 1 second. When the rocket descends through the main altitude set with the dial switch, the main chute fires for 1 second. When the rocket lands and the vertical velocity goes to zero, the data stops recording and the Sparrow starts beeping out the maximum altitude.
There is the same large, on-board capacitor to keep the altimeter running during deployment firings that the Raven uses. Since the Sparrow takes even less power, it will stay up even longer without any power input. So if you have a hard short that makes the battery voltage to go zero for either or both deployment outputs, the Sparrow will keep on humming throughout the event. The FETs are each rated for over 25 Amps continuous, so people who choose to use relatively large lipo batteries for the Sparrow XS don't have to worry about burning out a FET.
Power cycle the Sparrow and it's ready to go again. It will automatically save the most recent 5 flights worth of data, erasing the oldest flight as needed so that it's always ready to go. If a single flight takes longer than 40 minutes, and if the memory for the next flight has been cleared, the recording will continue into the next flight slot. A flight up to 3.4 hours can be recorded this way. To free up contiguous slots for a long flight (like a balloon flight, for example) you can erase any or all of the 5 flight slots with the computer interface. The Featherweight Interface Program will be updated to perform all of the interface functions for the Sparrow, and will provide derived data such as altitude and velocity.
Both versions of the Sparrow are mounted through two 4-40 size, grounded screw holes. No need to worry about insulating spacers or conductive sleds.
You can set the main chute altitude in the field with a simple rotary switch, in 100 foot increments up to 1500 feet. If you ever want to know what the main chute deployment altitude is set to, no need to power it on or look up jumper settings, just read the number indicated on the dial. The switch is a 16-position DIP switch labeled 0-9 then A-F. 1 is 100 feet, 9 is 900 feet, A is 1000 feet, F is 1500 feet, etc. I'm not yet sure what's the best use for the 0 setting; for now it will also just fire at 100 feet.
When you power it up, there is an immediate beep, followed by a beep-out of the battery voltage in 10ths of a volt.
Then it beeps out the continuity status of the 2 channels. A high beep and a green LED indicates the channel has continuity. A long, lower beep and a red LED flash indicates no continuity for that channel. (Just like the Raven, but with 2 channels instead of 4, and with color-coded LEDs for clarity) The altimeter is ready for launch. The altimeter uses a piezo buzzer that consumes much, much less power than the one used on the Raven, significantly improving the battery life. I'm not sure yet how long it can hang out at the pad with the smallest batteries, but it will be many hours.
The pad altitude is updated continuously, with enough time lag so that even a very slow launch won't be mistaken for a change in pad altitude. The altitude used for liftoff detection is filtered so that a transient from the rocket being dropped, etc. won't be mistaken for liftoff. Several seconds of data is continuously buffered so that all of the flight is recorded, even for a slow liftoff that delays the liftoff detection.
After liftoff, the altimeter records at 20 Hz the raw baro pressure in 1/25000 of an atm, temperature with 0.2F resolution, battery voltage, apogee channel voltage, and main chute voltage with 15 mV resolution. Also recorded is a digital flight events register that includes all of the flight event states that are used for deployment decisions (liftoff detection, velocity check status, apogee detection, altitude < main chute setpoint, and which channels fired). Velocity and other derived measurements that are calculated for use on board and can be reconstructed after the flight are omitted from the recording to maximize space. The Sparrow also records the pad altitude and flight number (odometer reading) in a 1-time slot at the start of the flight.
During the flight, the altimeter uses a combination of filters so than any spurious barometric data spikes are thrown out, and then the validated data is smoothed from there. Velocity is calculated and smoothed again before it is used, so that it's reliable for the deployment logic. Both channels are set to check that the vertical velocity is well under the level at which Mach effects can affect the data, for at least 2 seconds. When the rocket starts to descend, the apogee charge fires for 1 second. When the rocket descends through the main altitude set with the dial switch, the main chute fires for 1 second. When the rocket lands and the vertical velocity goes to zero, the data stops recording and the Sparrow starts beeping out the maximum altitude.
There is the same large, on-board capacitor to keep the altimeter running during deployment firings that the Raven uses. Since the Sparrow takes even less power, it will stay up even longer without any power input. So if you have a hard short that makes the battery voltage to go zero for either or both deployment outputs, the Sparrow will keep on humming throughout the event. The FETs are each rated for over 25 Amps continuous, so people who choose to use relatively large lipo batteries for the Sparrow XS don't have to worry about burning out a FET.
Power cycle the Sparrow and it's ready to go again. It will automatically save the most recent 5 flights worth of data, erasing the oldest flight as needed so that it's always ready to go. If a single flight takes longer than 40 minutes, and if the memory for the next flight has been cleared, the recording will continue into the next flight slot. A flight up to 3.4 hours can be recorded this way. To free up contiguous slots for a long flight (like a balloon flight, for example) you can erase any or all of the 5 flight slots with the computer interface. The Featherweight Interface Program will be updated to perform all of the interface functions for the Sparrow, and will provide derived data such as altitude and velocity.
My professors always said knowing HEX would come in handy.
HEX is my worst nightmare. Darn assembly language.
The first-ever Sparrow flight today was a complete success. I flew with LUNAR at Moffett Field. The max allowable altitude was 1000 feet, so I went with a BT70-based rocket flying on an E15 single-use motor, and I set the main altitude for 300 feet. There were hundreds of people at the launch, mostly scouts, so I was feeling the pressure when the LCO announced the flight and pointed out the new Sparrow altimeter. It was a great feeling to see the main pop out at the appointed altitude.
Here is the av-bay I flew today, with the Sparrow powered through a magnetic switch. For scale, the threaded rod is 4-40, the magnetic switch is the size of a dime, and an RRC3 would be a little longer than the whole sled. :wink: The purple/gold board color is due to this board being an OshPark prototype. The production boards will be green to keep the cost down (yes, there is a substantial cost difference!)
Here is the data from the flight, plotted in Excel. The Featherweight Interface Program isn't yet modified for the Sparrow, but that will happen soon.
Uploaded with ImageShack.com
Here's another close-up of the av-bay, where you can see one of the threaded rods that has the dual purpose of holding the bulkheads together and providing the 2 electrical connections for the apogee charge. The main charge uses the +Arm out threaded rod at the bottom, plus a short threaded rod for the other main charge terminal.
Uploaded with ImageShack.com
Here is the av-bay I flew today, with the Sparrow powered through a magnetic switch. For scale, the threaded rod is 4-40, the magnetic switch is the size of a dime, and an RRC3 would be a little longer than the whole sled. :wink: The purple/gold board color is due to this board being an OshPark prototype. The production boards will be green to keep the cost down (yes, there is a substantial cost difference!)
Here is the data from the flight, plotted in Excel. The Featherweight Interface Program isn't yet modified for the Sparrow, but that will happen soon.
Uploaded with ImageShack.comHere's another close-up of the av-bay, where you can see one of the threaded rods that has the dual purpose of holding the bulkheads together and providing the 2 electrical connections for the apogee charge. The main charge uses the +Arm out threaded rod at the bottom, plus a short threaded rod for the other main charge terminal.
Uploaded with ImageShack.com
Coop
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Very nice--like that av-bay setup with the threaded rods acting as conductors--elegant in its simplicity, yet clever. Will have to steal that in the future. Also quite pleased to hear of a successful first flight! Congrats--and looking forward to being able to have my own!
Later!
--Coop
Later!
--Coop
Thanks. What I like best about them is that they make great, durable terminal posts for connecting the charge wires, and they seal off the av-bay nicely with no electrical connectors.
Thanks for sharing your avbay setup. What battery did you use?
A 130 mAhr lipo.
Consider one sold already! Looks fantastic.
Ken
Ken
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+1 or maybe +2
maxvelocity
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Love it! Can't wait to get my hands on some of those!
Thanks, guys. I'll be setting up a beta test program next. The Raven beta testing a couple of years ago was o.k., but frankly not all that helpful to the Raven development. I'd like to do better this time, so here are my expectations for beta testers:
1. Pay close attention to anything that seems unexpected whenever you interact with the altimeter, and write it down in the beta test forum. We tend to forget what seemed unexpected or annoying about an interface once we get used to a new product, so please start looking for issues from the first time you open the package.
2. Fly at least 3 flights within 3 weeks of getting the unit, and post all data to the beta test forum.
3. Use it on your most unusual flights. High speed, low speed, high altitude, multi-stage (as a 2nd altimeter).
4. If a firmware update is necessary during the test program, ship it back and re-fly with new firmware
5. Fly it under different environmental conditions, if possible. Windy, hot, cold. The Raven had a bug that only was revealed when I flew it in cold temperatures after production started. There's only so much you can do this time of year, though.
6. Fly it with transmitters operating nearby, if possible.
You get the idea. See if you can find an operating condition in which the Sparrow doesn't work, and note any user interface problems that can be fixed. There will be a limited number of beta test units available. The only charge for the beta units will be completing items 1-4, and as much of 5-6 as you can. Please PM me if you're interested.
1. Pay close attention to anything that seems unexpected whenever you interact with the altimeter, and write it down in the beta test forum. We tend to forget what seemed unexpected or annoying about an interface once we get used to a new product, so please start looking for issues from the first time you open the package.
2. Fly at least 3 flights within 3 weeks of getting the unit, and post all data to the beta test forum.
3. Use it on your most unusual flights. High speed, low speed, high altitude, multi-stage (as a 2nd altimeter).
4. If a firmware update is necessary during the test program, ship it back and re-fly with new firmware
5. Fly it under different environmental conditions, if possible. Windy, hot, cold. The Raven had a bug that only was revealed when I flew it in cold temperatures after production started. There's only so much you can do this time of year, though.
6. Fly it with transmitters operating nearby, if possible.
You get the idea. See if you can find an operating condition in which the Sparrow doesn't work, and note any user interface problems that can be fixed. There will be a limited number of beta test units available. The only charge for the beta units will be completing items 1-4, and as much of 5-6 as you can. Please PM me if you're interested.
Green Jello
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I'm totally gonna do that, but I'm using this one:Have you tried this?
It's what I do and it works like a charm. I'm not hard of hearing, and I had issues discerning between two Ravens beeping away in the AV bay. Folks will snicker at you, but who cares? It works so well I'm amazed that everyone doesn't auscultate their rockets!
All the best, James
thobin
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I have re-read this thread a few times, while i'm not new to DD I have only used a few of the altimeters out there. And one of my biggest pet peeves of DD is that it is more complex than it needs to be. I personally would think the Sparrow EZ would be the bees knees. The less you have to set up and mess with the less that can go wrong, less work more time flyin. I don't build rockets without DD anymore and working AV bays is my least favorite task, so a one all included altimeter would really hit the spot.
With the size of the Sparrow XS you could hide one behind your ear and no one would know, just shy of 2 inches long and barley 5/8 of an inch wide! An excellent choice for a back up in a existing AV bay, or just plain retrofitting a rocket without.
I wish I could remember what I voted for when this thread started, because my vote now is both.
TA
With the size of the Sparrow XS you could hide one behind your ear and no one would know, just shy of 2 inches long and barley 5/8 of an inch wide! An excellent choice for a back up in a existing AV bay, or just plain retrofitting a rocket without.
I wish I could remember what I voted for when this thread started, because my vote now is both.
TA
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I've got a minimum diameter, minimum mass rocket going up on an I1299, if I can will myself to dare to do it. There will be some very harsh acceleration there and would be a fine test bed if there wasn't an Adept DDC 22 smashed in there already. If it survives, and If I can find it I would like to test the Sparrow. Alas, I don't get out much and the likelihood of me being a viable candidate for testing is very low.
-Ken
-Ken
I am a doctor and I always carry a stethoscope at launches. Now days, since I am more administrative, I use it more at the launches.
Adrian,
We discussed using LED's as continuity and status indication of the unit.
You mention that a green blink indicates continuity on the channel. What about multiple channels? And overall status of the unit?
I would really like to get one or two of these to accompany some of my other altimeters but want to be sure that they feature 100% user interaction for those who are hard of hearing/deaf (like myself). I realize I'm mentioning this a little too late since you have already produced the prototype and are probably about to enter the beta phase, but wanted to ask anyway.
Thanks.
Mike
We discussed using LED's as continuity and status indication of the unit.
You mention that a green blink indicates continuity on the channel. What about multiple channels? And overall status of the unit?
I would really like to get one or two of these to accompany some of my other altimeters but want to be sure that they feature 100% user interaction for those who are hard of hearing/deaf (like myself). I realize I'm mentioning this a little too late since you have already produced the prototype and are probably about to enter the beta phase, but wanted to ask anyway.
Thanks.
Mike
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