Introducing the Featherweight Blue Jay altimeter

[Dave S.]

I just wanted to chime in here that this is a fantastic idea!

Got my NAR Level 2 with a 4" diameter Formula 98 and your Blue Raven. I have only flown that rocket twice, but the Blue Raven has worked flawlessly both times. Its good the Blue Raven comes with a 2nd channel for the Apogee and the Main chute, but many smaller rockets will do fine with one charge for each like this one will have.

The thing that made me get the Blue Raven as my first DD altimeter is the ability with that Powerperch to turn it on/off with a magnet instead of an actual switch of some sort. The Blue Raven ground test mode is awesome too. I have seen a bunch of videos of ground tests with vacuum cleaners hooked up to the electronics bay - way too complicated.

With the Blue Jay it doesn't look like you would even need a powerperch - just the magnet.

 

[Adrian A]

I just wanted to chime in here that this is a fantastic idea!

Got my NAR Level 2 with a 4" diameter Formula 98 and your Blue Raven. I have only flown that rocket twice, but the Blue Raven has worked flawlessly both times. Its good the Blue Raven comes with a 2nd channel for the Apogee and the Main chute, but many smaller rockets will do fine with one charge for each like this one will have.

The thing that made me get the Blue Raven as my first DD altimeter is the ability with that Powerperch to turn it on/off with a magnet instead of an actual switch of some sort. The Blue Raven ground test mode is awesome too. I have seen a bunch of videos of ground tests with vacuum cleaners hooked up to the electronics bay - way too complicated.

With the Blue Jay it doesn't look like you would even need a powerperch - just the magnet.

That's correct.


A little update today. For most of the last week I have been struggling with getting the Blue Jay's over-the-air updates to work. I got that resolved today, so now I just need to finish my programming and test fixture and then I'll have production units available. My app developer is making progress and will likely be done with the Blue Jay-specific updates around the same time (maybe next week)

In the meantime, I have put together this table explaining the differences and similarities between the different models of Featherweight altimeters:



Edited table for clarity and formatting

 

[KAD]

I haven't decided about staging yet. It may be an optional (+$20) feature, and it would only be compatible for ematches.

I flew it in an 18mm body tube a few months ago. It won't fit into an 18mm coupler though.

I would also be interested in staging instead of main parachute. Maybe you could add soldering jumper on pcb. So anyone can decide what he needs. To fit inside 18mm tube, buzzer should be soldered infront of pcb. Also connectors could be smaller. Or maybe option without soldered connectors and buzzer.

 

[KAD]

Rocketflite.com has the hottest pyrogen on the market
5400deg F. They make very low current very small diameter igniters that will fit into 18mm composite C motors. Great for clusters.
They make the famous Magnalite pyrogen
and Clusterfire pyrogen.

Why not do DIY igniters. I use thin resistor wire from 15ohm 5W resistors in ceramic housing. They work even on small 100mAh single cell lipos.

 

[Bill Owens]

I'm really looking forward to the Blue Jay as well, and plan to get a few as soon as they are available. @Adrian A , might you be able to share the mounting hole dimensions? The pictures make it look more compact than the Raven and I'm already designing it into a new project.

 

[Adrian A]

The holes are just large enough for 4-40 screws (supplied)

 

[Adrian A]

Since you can mount it in any orientation, this might be more useful:

 

[bad_idea]

View attachment 673831

The holes are just large enough for 4-40 screws (supplied)

Will M2 work in place of 4-40?

 

[RokitFlyr]

Will M2 work in place of 4-40?

Look up the dimensions and let us know.

 

[pugachu]

Will M2 work in place of 4-40?

2mm is 0.079" #4-40 is 0.112" a m2.5 would be closer

 

[bad_idea]

Look up the dimensions and let us know.

2mm is 0.079" #4-40 is 0.112" a m2.5 would be closer

I am perfectly aware of the dimensions. What I am wondering is if in Adrian's opinion the mount will be adequately secure if I use M2 instead of 4-40.

 

[KAD]

I am perfectly aware of the dimensions. What I am wondering is if in Adrian's opinion the mount will be adequately secure if I use M2 instead of 4-40.

if you own 3D printer, you can make simple adapter board that is secured with M2 screws.

 

[Adrian A]

I am perfectly aware of the dimensions. What I am wondering is if in Adrian's opinion the mount will be adequately secure if I use M2 instead of 4-40.

Yes, that should be fine. The board only weighs a few grams.

 

[bad_idea]

Yes, that should be fine. The board only weighs a few grams.

Thanks. Thought as much but figured I might as well ask the horse's mouth.

 

[Neutronium95]

This might sound silly, but how well would it perform if it was wrapped in a bit of foam and tape and just left floating in a section of tube? I'm thinking about getting a few, and one would replace the EasyMini that I used to have in my BMS 3" School Rocket, which I just left floating in the payload bay.

 

[Adrian A]

This might sound silly, but how well would it perform if it was wrapped in a bit of foam and tape and just left floating in a section of tube? I'm thinking about getting a few, and one would replace the EasyMini that I used to have in my BMS 3" School Rocket, which I just left floating in the payload bay.

If it rotates relative to the rocket after liftoff, the tilt will be off by that much, but that’s usually not going to be a big deal.

 

[Adrian A]

My programming scrips are working well. The production testing firmware is coming along and will hopefully be done tomorrow. Then I’ll make them orderable.

 

[Dave S.]

I’ve only ever done two dual deployment flights - both with your Blue Raven altimeter.

The preparation before the flight is a lot more than for a motor eject flight, but it just seems to work.

I should be clear that part of the reason there was a lot of work for me was that I did dual deploy with a DMS motor both times. I set the motor eject charge timing to be a couple seconds after what Openrocket predicted would be the correct time for the apogee.

(I checked afterwards and both apogee charges fired from the Blue Raven as well as the motor eject DMS charge.)

 

[Adrian A]

I think I jinxed it with my post yesterday. Endless IDE toolchain problems today.

 

[Adrian A]

Too many simultaneous USB ports and/or too many breakpoints was making my IDE debugger unhappy in inconsistent ways. But I've gotten past that now and the test software is mostly working. There is enough variation in the analog readings though that I will need to make some on-board adjustments to the calibration coefficients during the test process. That will need to be tomorrow's task.

 

[bandman444]

The website page mentions no raw accelerometer data recorded, and the chart implies no accelerometer recording at all. What information is included for post flight analysis, and would the Blue Jay be capable of backing out thrust curves and rocket drag? I’m in love with the Blue Raven, but the price and common wiring scheme has kept me away for years. My last BALLS flight just took out my fleet of EasyMinis, so I’m excited to see other options in the $60-$80 range (Stratologgers, Easy Minis, RRC3s) and finally one with an accelerometer.

You also mentioned a slight modification to the hardware in the next batch to modify something about the switch. Will there be a guide published on how to remove the mag switch and replace it with a conventional switch for use in applications where a mag switches may not be viable?

 

[FlyAwaySam]

Idea based on the naming scheme of the altimeters: name the Featherweight Tracker the Blue Whale. My thoughts go with the echolocation of whales. The GPS pings its location to the ground station. I know it isn't a 1-1 comparison but why not.

 

[Adrian A]

The website page mentions no raw accelerometer data recorded, and the chart implies no accelerometer recording at all. What information is included for post flight analysis, and would the Blue Jay be capable of backing out thrust curves and rocket drag? I’m in love with the Blue Raven, but the price and common wiring scheme has kept me away for years. My last BALLS flight just took out my fleet of EasyMinis, so I’m excited to see other options in the $60-$80 range (Stratologgers, Easy Minis, RRC3s) and finally one with an accelerometer.

If you want to calculate thrust curves and rocket drag, the Blue Raven is the product designed for that use case. It's as good of a value as I can make it, considering my development costs for it and the accompanying phone app. You can add a power perch or a simple circuits board if you don't want to put multiple wires into one terminal.

The Blue Jay isn't intended to be a Blue Raven replacement; it's designed primarily for entry-level flyers and people who don't care about recorded data, or for advanced flyers who want a small backup altimeter. There isn't room on the Blue Jay's flash chip to do the high speed accel and gyro recording of the Blue Raven. The Blue Jay still records enough information to diagnose a failed deployment or an output not turning on when expected, along with speed, altitude, tilt, roll, etc that most people are most interested in.

You also mentioned a slight modification to the hardware in the next batch to modify something about the switch. Will there be a guide published on how to remove the mag switch and replace it with a conventional switch for use in applications where a mag switches may not be viable?

Yes. If you don't want to use the magnetic switch, you can solder a jumper wire on the current hardware to bypass it. The next rev that's getting made now makes it easier to bypass with just a solder bridge.

 

[Adrian A]

Idea based on the naming scheme of the altimeters: name the Featherweight Tracker the Blue Whale. My thoughts go with the echolocation of whales. The GPS pings its location to the ground station. I know it isn't a 1-1 comparison but why not.

I see your point about pings, but if I made an altimeter called the Blue Whale it would need to be at least as large as the largest rocketry electronics out there.

 

[FlyAwaySam]

I see your point about pings, but if I made an altimeter called the Blue Whale it would need to be at least as large as the largest rocketry electronics out there.

Another thought was Blue Pigeon because carrier pigeon. I know the blue part doesn't fit too well as no Bluetooth.
Unrelated to anything else, do you think it will be possible in the future to have the app have an option to do metric units?

 

[bandman444]

$130 price difference ($210 for BR + PP) for 5 seconds of 50Hz accelerometer data is a bit much. Double if you want two redundant altimeters.

I don’t really want to suggest it, but maybe another $20 option to software-unlock a low rate accelerometer recording upgrade could be valuable?

 

[Neutronium95]

I see your point about pings, but if I made an altimeter called the Blue Whale it would need to be at least as large as the largest rocketry electronics out there.

I for one would love to see how much capability you could cram intonthe volume of Kate 3. Probably something along the lines of a full on PC...

 

[KAD]

Blue Jay Plus version is just unlocked version blue jay? So we can select between main chute or staging? Or there are some extra features for those extra $20?

 

[SolarYellow]

1. I searched this thread and the web page and didn't see the mass in grams called out anywhere.

2. If someone wanted to minimize mass further, might it be possible at some point to get the BJP boards with the terminal block and buzzer not installed?

 

[Adrian A]

$130 price difference ($210 for BR + PP) for 5 seconds of 50Hz accelerometer data is a bit much. Double if you want two redundant altimeters.

I don’t really want to suggest it, but maybe another $20 option to software-unlock a low rate accelerometer recording upgrade could be valuable?

I hear you and I get it. There's just a tension between wanting to make the Blue Jay as capable as it can be and still keeping it distinct from the Blue Raven. I'll see how things go after the Blue Jay is available before making any changes to the plan.

Blue Jay Plus version is just unlocked version blue jay? So we can select between main chute or staging? Or there are some extra features for those extra $20?

All the features I could think of are in the feature comparison table. Is there one you're wondering about that is missing from there?

1. I searched this thread and the web page and didn't see the mass in grams called out anywhere.

4.7 grams

2. If someone wanted to minimize mass further, might it be possible at some point to get the BJP boards with the terminal block and buzzer not installed?

You could cut them off, but I'm not planning to carry a different assembly version for that.