basic questions on Featherweight altimeter and the GPS system

[Dave S.]

I am a little confused on how the Featherweight altimeter and the GPS system work.

For the GPS there is the component that goes on the rocket and the blue groundstation unit. I am not clear on how the groundstation is used. There are only a couple LEDs on it, so how do you know what direction to go in and how far to retrieve the rocket? How do you know if your groundstation is synched to your onboard GPS or someone elses? Does the GPS system have anything to do with your phone? Or is the phone app only for the altimeter?

For the altimeter - is there a test function that you an use with the app on your phone to do a ground test? If not - how do you trigger it for a ground test to figure out how much BP to load in the rocket?


Thanks!

 

[manixFan]

Right now you use an iOS app to connect to the GPS ground station. It tells you everything you want to know. Unfortunately, there isn’t an Android app available now, but it is in active development.

For the Blue Raven, there are both Android and iOS apps to connect to it. You can use the Blue Raven to run ground tests for ejection charges.


Tony.

PS: there are many threads on both units with screenshots and explanations. A little reviewing of those threads will explain a lot.

Plus, here’s what’s happening with the updated app:

https://www.rocketryforum.com/threa...one-app-available-for-android-and-ios.183123/

 

[Conway Stevens]

Right now you use an iOS app to connect to the GPS ground station. It tells you everything you want to know. Unfortunately, there isn’t an Android app available now, but it is in active development.

For the Blue Raven, there are both Android and iOS apps to connect to it. You can use the Blue Raven to run ground tests for ejection charges.


Tony.

PS: there are many threads on both units with screenshots and explanations. A little reviewing of those threads will explain a lot.

Plus, here’s what’s happening with the updated app:

https://www.rocketryforum.com/threa...one-app-available-for-android-and-ios.183123/

Tony,

Technically that answer just changed/starting to change in the last 24 hours. Tracking has just been released via the Blue Raven software. You now have Altimeter data/control as well as Tracking on both Iphone and Android being released through the latest update. Still. Id assume without testing the most reliable is the current seperate tracking app via Iphone. But i have yet to use the current app yet. It does have some features that are normally used still being added. But here are some screen shots.

 

[manixFan]

Tony,

Technically that answer just changed/starting to change in the last 24 hours. Tracking has just been released via the Blue Raven software. You now have Altimeter data/control as well as Tracking on both Iphone and Android being released through the latest update. Still. Id assume without testing the most reliable is the current seperate tracking app via Iphone. But i have yet to use the current app yet. It does have some features that are normally used still being added. But here are some screen shots.

I must have edited my post while you were replying, as I linked to Adrian’s announcement. Very cool to see the screenshots, and to have the beta on my devices.

It just keeps getting better.


Tony

 

[Conway Stevens]

I must have edited my post while you were replying, as I linked to Adrian’s announcement. Very cool to see the screenshots, and to have the beta on my devices.

It just keeps getting better.


Tony

Agreed my friend!

 

[thzero]

You need an iOS device with the featherweight software installed.

An updated software is currently in beta that supports both iOS and android devices.

The GPS tracker connects to ground station. The device connects to the ground station and software on device displays where to find the rocket.
The software also shows which groundstations and trackers are connected and how many satellites etc they are receiving signal from.

Raven altimeter I've not used. The new blueraven can connect to is the device app with Bluetooth to manage the altimeter settings and remotely trigger a test.

Featherweight has pretty good documentation.

 

[Dave S.]

Thanks for your replies. I have gone back and looked at the official web page and other TRF conversations and it is much clearer now.

Being able to remotely trigger firings for ground tests is an important feature. That would make the testing so much easier vs. a test that involves a vacuum cleaner or some other work around. If you are trying to do the test where there are no electric outlets (a park or a local field), the vacuum method will not work. Remote triggering will just be best.

I like the way the altimeter can be turned on hands free inside a sealed-up rocket w/ the magnetic switch! What about the GPS unit that goes inside the rocket?


Thanks!

 

[kjhambrick]

Thanks for your replies. I have gone back and looked at the official web page and other TRF conversations and it is much clearer now.

Being able to remotely trigger firings for ground tests is an important feature. That would make the testing so much easier vs. a test that involves a vacuum cleaner or some other work around. If you are trying to do the test where there are no electric outlets (a park or a local field), the vacuum method will not work. Remote triggering will just be best.

I like the way the altimeter can be turned on hands free inside a sealed-up rocket w/ the magnetic switch! What about the GPS unit that goes inside the rocket?

Dave --

I love the Featherweight Mag Switch !

Adrian has installed Mag Switches on his GPS: Adding a magnetic switch to a Featherweight GPS tracker

It looks pretty simple even for someone with my soldering skillz

-- kjh

 

[thzero]

I can't stand the nag switches myself. I just give myself struggling to know if it's on or off. The idea is great.

Generally I wait until last moment to turn on GPS tracker and my altimeters with the pull pins having a physical disconnect between the altimeter and ejection charges. Then on rail I pull the pins, and arm the altimeters. That's process I do with eggtimer quantums. Same I'd follow as I get the blueraven working in some setups

But otherwise yes being a fan of eggtimer quantum's, being able to remote test and arm is great.

 

[Dave S.]

The eggtimer Quasar is an all in one altimeter and gps, but a kit that needs to be assembled. Same for the eggtimer gps groundstation unit.

 

[thzero]

The eggtimer Quasar is an all in one altimeter and gps, but a kit that needs to be assembled. Same for the eggtimer gps groundstation unit.

Yup. But what ends up working for those remotely activated devices works for featherweight stuff to... Process wise

 

[Dave S.]

Being able to use a 2nd magnetic switch for the GPS is a great option. (The 1st magnetic switch for the altimeter is part of the "Powerperch")

I have an unbuilt 4" diameter kit with a ebay coupler that is about 9 inches long.

Sounds like I could have two magnetic switches far enough apart to use both without interference. That would be perfect!

 

[thzero]

Should be able to, yes.

 

[Dave S.]

> I can't stand the nag switches myself. I just give myself struggling
> to know if it's on or off. The idea is great.


Can't you tell if the altimeter and the GPS onboard components are on or off with your cell phone?

 

[Adrian A]

Being able to use a 2nd magnetic switch for the GPS is a great option. (The 1st magnetic switch for the altimeter is part of the "Powerperch")

I have an unbuilt 4" diameter kit with a ebay coupler that is about 9 inches long.

Sounds like I could have two magnetic switches far enough apart to use both without interference. That would be perfect!

> I can't stand the nag switches myself. I just give myself struggling
> to know if it's on or off. The idea is great.


Can't you tell if the altimeter and the GPS onboard components are on or off with your cell phone?

Yes, the Blue Raven beeps immediately when it's turned on, and the Blue Raven and Featherweight GPS show up in the phone after a second or two.

Newer Featherweight magnetic products, including the latest magnetic switch, use a sensor that turns on when the field is one way, and turns off when the field is the other direction. This makes it much easier to reliably turn on two sets of devices together in the same av-bay because you can avoid accidentally turning one off when you're turning the other one on, as long as you orient them roughly the same way.

 

[kjhambrick]

> I can't stand the nag switches myself. I just give myself struggling
> to know if it's on or off. The idea is great.


Can't you tell if the altimeter and the GPS onboard components are on or off with your cell phone?

@Dave S. --

EDIT: too slow ! @Adrian A answered while I gathered photos for you ...

I have a Blue Raven but not a GPS.

Yes: It is obvious in the Blue Raven Phone App when the Blue Raven Altimeter has been turned on.

It appears in Adrian's latest post that the same is true for the GPS.

This is @Adrian A's latest thread: New Featherweight GPS phone app available for Android and iOS

Note the screen shot of the GPS.

This is what I see in my Android phone without a GPS turned on and connected via BlueTooth:


This is what I see when my Blue Raven is turned off:


This is after turning on the Blue Raven via the Mag Switch:


This is my q&d, flippable Magic Wand made from a Featherweight X-Large Magnet and a spent Estes 18mm motor case and a dowel, color coded for off / on.


HTH

-- kjh

 

[thzero]

And I haven't updated by BR software on Android to check it out with my Featherweight GPS tracker... just been using the iOS version... but will shortly.

 

[Dan Griffing]

I can't stand the nag switches myself. I just give myself struggling to know if it's on or off. The idea is great.

Generally I wait until last moment to turn on GPS tracker and my altimeters with the pull pins having a physical disconnect between the altimeter and ejection charges. Then on rail I pull the pins, and arm the altimeters. That's process I do with eggtimer quantums. Same I'd follow as I get the blueraven working in some setups

But otherwise yes being a fan of eggtimer quantum's, being able to remote test and arm is great.

I installed a spare RRC2 in parallel with my Featherweight GPS to my mag switch in my nosecone module so that I would get audio feedback to prove that the GPS was powered. The RRC2 also gives me a backup indicator about the altitude reached.

I love the mag switch because it allows me to easily turn the GPS on and off without taking the nosecone apart.

 

[Art Upton]

A shop Vac produces better testing then a Phone App....

If your Ebay is defective a Shop Vac will detect it instantly like it did for me once.... A Phone App will not....

 

[watheyak]

A shop Vac produces better testing then a Phone App....

If your Ebay is defective a Shop Vac will detect it instantly like it did for me once.... A Phone App will not....

Maybe of you're still using an Adept altimeter. It used to be fun rigging up Christmas lights so you don't waste your flashbulbs.

Can a modern accel/baro altimeter even be fooled by a Shop Vac? I would think the Kalman filter would ignore the contradictory change in baro.

 

[kjhambrick]

A shop Vac produces better testing then a Phone App....

If your Ebay is defective a Shop Vac will detect it instantly like it did for me once.... A Phone App will not....

@Art Upton --

What defect did you discover in your Ebay with the shop vac ?

Thanks.

-- kjh

 

[Adrian A]

A shop Vac produces better testing then a Phone App....

If your Ebay is defective a Shop Vac will detect it instantly like it did for me once.... A Phone App will not....

Maybe of you're still using an Adept altimeter. It used to be fun rigging up Christmas lights so you don't waste your flashbulbs.

Can a modern accel/baro altimeter even be fooled by a Shop Vac? I would think the Kalman filter would ignore the contradictory change in baro.

When you run the simulated flight in the app, you are testing everything but the health of the sensors. This includes:

• Deployment settings are correctly set to do what you want them to do (even complicated settings dependent on several sensors like airstarts)
• Battery is compatible and correctly wired
• Power switch works
• Data recording and download works

For the health of the sensors, that's what the color-coded live data is for. You can verify that the accels, gyros, and baro sensor are all working properly at the pad as the last thing before you walk away.

For testing the size of your deployment charge, the ground test feature works well for this, recording video as well as sensor data. There is a place to write notes about what size or configuration of charge you're using and the results, so that you can refer back to it months or years later.

A shop vac test can show you the altitude going up in the live data in case you're still wondering about the baro sensor health even after seeing that the sensor is working well enough to provide your correct* altitude above sea level. But it can't test much else on the Blue Raven because launch detection is done with the accelerometers.

*within +/- 400 feet due to weather systems

Edit: Art makes a good point that a shop vac test can detect an av-bay leak, which could cause corrosive gas to damage your electronics. Blue Raven altimeters are nearly immune to deployment charge pressure transients from a software point of view, but it’s still good to avoid gunking up the circuit boards.

 

[Tobes]

A shop Vac produces better testing then a Phone App....

If your Ebay is defective a Shop Vac will detect it instantly like it did for me once.... A Phone App will not....

Tthis is like where grandpa wakes up from his nap on the couch, yells some gibberish about the sideburns you don’t have, and falls back asleep.

There’s nothing instant about a shop vac test. Thanks to all the altimeter manufacturers for modernizing the hobby with an very capable iPhone app. And bringing us out of the shop vac dark ages.

 

[Dave S.]

Thanks to everyone for the very informative replies! There are a lot of altimeter options, but not all that many GPS systems. All the info was very helpful.

 

[Buckeye]

Maybe of you're still using an Adept altimeter. It used to be fun rigging up Christmas lights so you don't waste your flashbulbs.

Can a modern accel/baro altimeter even be fooled by a Shop Vac? I would think the Kalman filter would ignore the contradictory change in baro.

Agreed. Here is a thread where I vacuum-tested an older altimeter (MAWD) and a newer altimeter (SLCF).

https://www.rocketryforum.com/threads/weird-slcf-deployments-during-vacuum-test.165455/
The vacuum test is way too fast and gives unrealistic deployments.

 

[Art Upton]

I use a Shop Vac test on my Stratto Loggers to make sure the AV-bay and the Altimeter/charges will fire, not collect data.

As I stated in a past post, I discovered on my LOC ISP rocket I built the AV-bay with a leak in it and it would not fire.

I fixed the leak and then it would. It had a nice flight to almost 5,000 feet at Geneseo NSL 2018 on an I65-P, Used a Jolly Chute Release for the main.

 

[cerving]

As a general rule, if your AV bay is slightly leaky in the bulkplates (and most are...), it's not going to significantly affect flight performance. It's just an extra way of getting air into the AV bay, at least until the charges fire. Chances are that if you plug all the holes in the bulkplates it will be just fine... and minor ejection gas intrusion is unlikely to cause a malfunction with any modern baro altimeter.

Regarding the remote ejection charge test, it allows you to test your altimeter's output circuitry, your ematches, and your charge size, without having to stand right next to the rocket as it's firing. Maybe with a 38mm rocket with a 0.3 gram charge you might be OK with it, but with something like a 7.5" Polecat Thumper with 6 grams of BP you do not want to be standing next to it with a shop vacuum hose while it fires.

 

[Art Upton]

As a general rule, if your AV bay is slightly leaky in the bulkplates (and most are...), it's not going to significantly affect flight performance. It's just an extra way of getting air into the AV bay, at least until the charges fire. Chances are that if you plug all the holes in the bulkplates it will be just fine... and minor ejection gas intrusion is unlikely to cause a malfunction with any modern baro altimeter.

Regarding the remote ejection charge test, it allows you to test your altimeter's output circuitry, your ematches, and your charge size, without having to stand right next to the rocket as it's firing. Maybe with a 38mm rocket with a 0.3 gram charge you might be OK with it, but with something like a 7.5" Polecat Thumper with 6 grams of BP you do not want to be standing next to it with a shop vacuum hose while it fires.

Mine was not leaky at the bulk heads gaps to coupler per say, it had a leak I didn't think about in the mounting bolt into the upper payload bay that was not being used by a DD parachute but had an antenna in it. It was a large leak you really could not see really.

Fixed it and it worked fine. If I had not tested it , Apogee charge may not have happened.

 

[Dave S.]

Just wanted to say thanks to everyone who replied with very helpful info and the screenshots too!

I ended up getting a Blue Raven altimeter, power perch, magnet, battery, and charger. Now all I need to do is actually put together the fiberglass dual deploy rocket I have here sitting in a box.

 

[thzero]

Just wanted to say thanks to everyone who replied with very helpful info and the screenshots too!

I ended up getting a Blue Raven altimeter, power perch, magnet, battery, and charger. Now all I need to do is actually put together the fiberglass dual deploy rocket I have here sitting in a box.

Take it out of the box, put it back in the box..... its progress!