Featherweight Sparrow Altimeter

I'm working on 2 variations of a new, entry-level baro-only altimeter: the Featherweight Sparrow.

Both variations will feature:

• The same high-accuracy, digital-output barometric sensor that the Raven uses, usable to 100,000 feet
• 2 deployment outputs, apogee and main chute.
• An easy-to-use rotary DIP switch to select the main chute deployment altitude in 100 foot increments
• Easy-to-use, dual wire terminals for each deployment output
• A beeper for reporting battery voltage, continuity and max altitude
• Compatibility with single lithium polymer cells
• Data recording for over 1 hour of flight time, downloadable with an optional computer interface
• Outputs that stay on for 1 second, and can handle over 20 Amps without any risk of browning out the altimeter

The two versions are the Sparrow XS (for extra-small) and the Sparrow EZ, which is designed to be easier to use than any altimeter on the market today.

The Sparrow XS is expected to cost under $59 (maybe less, we'll see), will fit inside an 18mm coupler tube, and is under 2" long. It will have 6 wire terminals: 2 for a battery (anything from 3.6V to 14 V) and switch, and 2 each for the ematches.

The Sparrow EZ will be the hobby's only deployment altimeter with an integrated battery and magnetic switch. Just mount it on your sled, connect your ematches, and you're ready to fly it. No switch or battery wiring is required, and no switch access holes are needed, since at the pad you can just wave the included magnet next to your rocket to turn on the altimeter. The expected price for the Sparrow EZ will be $75, which would be like paying the normal combined price for the switch, battery, and battery connector, and getting a recording 2-axis deployment altimeter for only $40.

The Sparrow EZ's battery will be compatible with the existing $17 Featherweight battery charger, and I'll also be offering a combined USB download interface/battery charger that can download data from either Sparrow, and charge the Sparrow EZ's battery, for around $25.

I'm expecting to be done with the first production in about 3 months, so it's still early enough to incorporate feedback from this group if there's a feature I'm missing that would add value for most users. I admit I have had false alarms posting about development products in the past, :blush: so feel free to take this with a grain of salt. But this is a relatively simple design that has a lot in common with my previous designs and the Peregrine that I'm also working on, so I'm pretty confident I'll be able to get it done.

I sure don't miss the days of a cardboard triangle with a washer tied to a string looking thru a toilet tissue roll to figure altitude. It's only because smart guys like you can make dumb guys like me look good out on the range! Thanks, Adrian!

Adrian A said:

No switch or battery wiring is required, and no switch access holes are needed, since at the pad you can just wave the included magnet next to your rocket to turn on the altimeter.

Click to expand...

Assuming that the altimeter is mounted close enough to the outside of the rocket for this to work. This could easily be a minority opinion, but I find the magnetic switch to be problematic because one doesn't get good positive feedback when it's turned on or off. I'd personally be happier with an integrated screw switch.

For the poll, I think I'll say Sparrow XS only, though the integrated battery has an appeal.

Also, I really think to be competitive you need something more portable between platforms that the current FIP.

mikec said:

I find the magnetic switch to be problematic because one doesn't get good positive feedback when it's turned on or off.

Click to expand...

Thanks for the feedback. Good food for thought.

For those who haven't used this before, the beeper (and LED, if you have a hole with a line of sight to it) provides the indication about whether the altimeter is powered on or not. But it's true that there isn't any tactile indication.

Adrian A said:

Thanks for the feedback. Good food for thought.

For those who haven't used this before, the beeper (and LED, if you have a hole with a line of sight to it) provides the indication about whether the altimeter is powered on or not. But it's true that there isn't any tactile indication.

Click to expand...

The biggest issue I found is that when you pass the magnet by it takes a few seconds to start up and hear the beep.

But it seems the same with a normal switch, maybe faster start up?

BLKKROW said:

The biggest issue I found is that when you pass the magnet by it takes a few seconds to start up and hear the beep.

But it seems the same with a normal switch, maybe faster start up?

Click to expand...

Good idea. I should be able to provide a more immediate beep.

Adrian A said:

Good idea. I should be able to provide a more immediate beep.

Click to expand...

Maybe once power is on, a long start up beep. Then the usual continuity beeps.

I would definitely get the EZ if it had some other way to activate the switch in the case of an odd rocket design. Perhaps user solderable ports where you could wire a conventional switch.

mikec said:

Also, I really think to be competitive you need something more portable between platforms than the current FIP.

Click to expand...

To expand on this, since you aren't setting any of the altimeter parameters via the interface, define and document a simple protocol to request the recorded data to be downloaded, and someone will write a usable interface for it for platforms you don't feel like supporting yourself.

It would also be easy to support realtime transmission of the data stream (serial at some reasonable rate) for use if someone wanted to hook up a radio.

mikec said:

Assuming that the altimeter is mounted close enough to the outside of the rocket for this to work. This could easily be a minority opinion, but I find the magnetic switch to be problematic because one doesn't get good positive feedback when it's turned on or off. I'd personally be happier with an integrated screw switch.

For the poll, I think I'll say Sparrow XS only, though the integrated battery has an appeal.

Also, I really think to be competitive you need something more portable between platforms that the current FIP.

Click to expand...

agreed I WANT to mount a battery where I want it and I WANT to put MY switch where I want it//

Honestly, I would rather not have the magnetic switch ( I have 4 ravens, two power perches and a magnetic switch) and honestly it gives me more trouble than its really worth. Is it good for MD rockets? Oh HECK yes. but for everything else, I would much rather go with pretty much anything else (physical switch, twist-n-tuck, etc. ) the built in battery would be cool, but at the same time Im the kinda guy that would rather just swap batteries because with one of these I can definitely see myself just quick-changing the altimeter and swapping it to another av-bay/rocket and I would hate to have to wait for it to charge.

I think both set ups would sell, but I suspect the XS will sell more.

If you build the EZ you have one sold to me! I like the modular simplicity! Count me in for your support.

At a close future point I can see me progressing stepping up to the next model LX I can see a market for both

Adrian, I voted for the XS because I want to decide what battery and what switch I want to use.

I voted for the XS, but what I would really want is a hybrid of the two! I like the onboard battery of the EZ, but the switch terminals on the XS. If a user wanted to use a magnetic switch, they could purchase one of your stand alone units and wire that up.

LiPo's are definitely feasible in the hobby. The XS with onboard LiPo sounds like a small footprint throwback RRC2.

This is looking to be a good year for those looking for a new altimeter!

-Kevin

2013 is the year of the Altimeter I think (sorry Tim )

I put both. An inexpensive baro-only altimeter is JUST what I need for a couple of projects the kids have me talked into (not that it took much), and could see definite advantages of both versions discussed above.


Later!

--Coop

As nice as some of the other new altimeters look, I would buy the Sparrow EZ for every new DD rocket just to save the time and potential failure points in wiring up an av-bay. I really like the simplicity in an all-in-one approach. While there are small altimeters out there (Telemetrum Mini?), there is no all-in-one offering available. How many threads have we seen on TRF for the widely loved Olsen that had an LCD screen and integrated battery holder? This would be even better, especially if it could have a removable LCD. It would appeal to experienced flyers for the simplicity and inexperienced flyers new to DD. All of those questions like which battery to use, how to mount it, what gauge wire to use, what switch, etc, etc, would be eliminated.

I don't need a super-small altimeter, but I WILL buy at least 5-6 Sparrow EZ's in the coming year if they are made--count me in.

BLKKROW said:

The biggest issue I found is that when you pass the magnet by it takes a few seconds to start up and hear the beep.

But it seems the same with a normal switch, maybe faster start up?

Click to expand...

A few times I waved the magnet over the right area, didn't hear anything, then started to wave the magnet again when I started to hear the beeps as the magnet went over again--a few times too late to avoid turning it off again. A quicker on/off response would be great. Also, a specific, loud signal to signify turning off would help (could you borrow that Win7 shut down sound??).

I haven't used a magnetic switch, but an immediate and distinct beep when it turns on would be a major attraction. That strikes me as what should clearly be the standard practice in electronics if we're going to expect to use magnetic switches (or if we ever go to arming by radio).

CarVac said:

I would definitely get the EZ if it had some other way to activate the switch in the case of an odd rocket design. Perhaps user solderable ports where you could wire a conventional switch.

Click to expand...

I think it should be possible to accommodate that without taking away from the magnetic switch design. I'll look into it.

mikec said:

To expand on this, since you aren't setting any of the altimeter parameters via the interface, define and document a simple protocol to request the recorded data to be downloaded, and someone will write a usable interface for it for platforms you don't feel like supporting yourself.

It would also be easy to support realtime transmission of the data stream (serial at some reasonable rate) for use if someone wanted to hook up a radio.

Click to expand...

Good reminder about the real-time data stream. That's a feature I'm planning to support.

Viperfixr said:

As nice as some of the other new altimeters look, I would buy the Sparrow EZ for every new DD rocket just to save the time and potential failure points in wiring up an av-bay. I really like the simplicity in an all-in-one approach. While there are small altimeters out there (Telemetrum Mini?), there is no all-in-one offering available. How many threads have we seen on TRF for the widely loved Olsen that had an LCD screen and integrated battery holder? This would be even better, especially if it could have a removable LCD. It would appeal to experienced flyers for the simplicity and inexperienced flyers new to DD. All of those questions like which battery to use, how to mount it, what gauge wire to use, what switch, etc, etc, would be eliminated.

I don't need a super-small altimeter, but I WILL buy at least 5-6 Sparrow EZ's in the coming year if they are made--count me in.

Click to expand...

Thanks for the feedback. My goal for the EZ is for it to be the favorite answer answer for the common question: "I'm new to DD, what altimeter should I get?"

The responses here are confirming what I suspected, that there are a lot of people who really like the integrated approach with the magnetic switch, and a lot of people who really don't. (Hopefully the feedback and ideas on improving the beep for magnetic switches will also help reduce the latter category) I think that making two versions will be worth the effort.

Viperfixr said:

A few times I waved the magnet over the right area, didn't hear anything, then started to wave the magnet again when I started to hear the beeps as the magnet went over again--a few times too late to avoid turning it off again. A quicker on/off response would be great. Also, a specific, loud signal to signify turning off would help (could you borrow that Win7 shut down sound??).

Click to expand...

Yes, I can do that. I had been about to respond before that I could make the altimeter beep whenever the magnet is in range, but I realized that I could only do that for the turn-off part. (the switch only turns on when the magnet comes in range and then goes away) I'll give a turn-off beep a try and we'll see if that helps.

Adrian - can you make the EZ with a jumper (or microswitch) to bypass the magnetic switch? That way those who want a hard switch, or want to mount this in the middle of a 4" rocket, can just put a twist-wire or external switch in series with the battery.

My only complaint about the magnetic switch is that I have an older one which is pole sensitive, so I have to mark my magnet poles on and off, but I understand that the v3 ravens are activated by mere field presence. I will say that with the bigger magnet it's not nearly as hard to arm as with the little one. If I could make a request it would be that you have an on and off tone pair - two tones ascending for on and two tones decending for off. A 1.5:1 frequency ratio would be great.

Would the integrated battery be soldered to the board, or could it be an Eflight port and strap or other holder?

Will the EZ still fit in an 18mm coupler, or will it be a 24mm coupler part?

JordanT said:

Adrian - can you make the EZ with a jumper (or microswitch) to bypass the magnetic switch? That way those who want a hard switch, or want to mount this in the middle of a 4" rocket, can just put a twist-wire or external switch in series with the battery.

Click to expand...

I'm pretty sure I can add a couple of spots for a user to solder his own external switch, without getting in the way of people who order the EZ for its magnetic switch.

JordanT said:

Would the integrated battery be soldered to the board, or could it be an Eflight port and strap or other holder?

Click to expand...

It will be very similar to the battery setup on the Power Perch, but with the deployment terminals along the side of the battery where the Raven is attached to the Perch.

JordanT said:

Will the EZ still fit in an 18mm coupler, or will it be a 24mm coupler part?

Click to expand...

24mm, so narrower than the Power Perch, which needs 38mm.

Viperfixr said:

As nice as some of the other new altimeters look, I would buy the Sparrow EZ for every new DD rocket just to save the time and potential failure points in wiring up an av-bay. I really like the simplicity in an all-in-one approach. While there are small altimeters out there (Telemetrum Mini?), there is no all-in-one offering available. How many threads have we seen on TRF for the widely loved Olsen that had an LCD screen and integrated battery holder? This would be even better, especially if it could have a removable LCD. It would appeal to experienced flyers for the simplicity and inexperienced flyers new to DD. All of those questions like which battery to use, how to mount it, what gauge wire to use, what switch, etc, etc, would be eliminated.

I don't need a super-small altimeter, but I WILL buy at least 5-6 Sparrow EZ's in the coming year if they are made--count me in.

Click to expand...

+1 for what Viper said.

I must be the unusual one. My AV bays are "keyed" so they can only go together one way; add marking exactly where the magnet is, and the magnetic switch has been simple and solidly reliable. It's been as easy as a light switch.




In the wish-for department...I would pay good money for a header to allow an external LED...



All the best, James

Put me in the category of those who like the magnetic switches. They require a little more planning, but I do like them

What I'm not so fond of is an integrated battery, and especially so if it's not user-replaceable without a soldering iron.

-Kevin

troj said:

Put me in the category of those who like the magnetic switches. They require a little more planning, but I do like them

Click to expand...

I believe what is really needed is a self-contained magnetic switch; something that doesn't need a battery feed from the altimeter and can be "remoted" anywhere on the rocket. I'm thinking a small profile board with integrated "micro-dot" LiPo that only needs charging once every 6 mos. or so and simply has two leads (and/or small terminals) for connection along with mounting via a single #2 screw. The above version would be so much easier to use than the soldering and half-baked mounting system in the current mag switch board, now whether it is actually doable is another thing....

dixontj93060 said:

I believe what is really needed is a self-contained magnetic switch; something that doesn't need a battery feed from the altimeter and can be "remoted" anywhere on the rocket. I'm thinking a small profile board with integrated "micro-dot" LiPo that only needs charging once every 6 mos. or so and simply has two leads (and/or small terminals) for connection along with mounting via a single #2 screw. The above version would be so much easier to use than the soldering and half-baked mounting system in the current mag switch board, now whether it is actually doable is another thing....

Click to expand...

How about if the switch instead used a small button cell?

-Kevin

I like integrated approach of EZ version for two reasons: it allows novice hobbyists easily use DD without being deterred by complexity; and easily add backup altimeter to existing DD design.

What would be useful (at least for me),

1) Report battery state - not in volts but in general terms (ex: 3 beeps = freshly charged, 2 = drained but still usable, 1 = unusable)

2) Use headers instead of wire terminals. This will make it easy to switch altimeter between rockets.

Altimeter can come with a cable, connector on one side and loose wire on the other; all the user has to do is solder color-coded wires to ejection charges and plug connector to the altimeter. EZ.

3) Start beeping as soon as power is turned on.

4) Make coffee and hot dogs.. uhmm.. that would be another project

-Alex

Adrian A said:

Yes, I can do that. I had been about to respond before that I could make the altimeter beep whenever the magnet is in range, but I realized that I could only do that for the turn-off part. (the switch only turns on when the magnet comes in range and then goes away) I'll give a turn-off beep a try and we'll see if that helps.

Click to expand...

So are you saying you cannot program the altimeter to BEEP then start the code for the altimeter?

At least for the two Ravens I have when the battery power is applied all the lights turn on then shortly after you start to hear the beeps. I don't know your code but I imagine its starting up the firmware and then once all of that is established it beeps out its code.

Why not have the power applied which immediately Beeps out the Piezo then start the firmware?

Sorry this is a feature that I greatly desire.