Low power GPS/Telemetry/Datalogging... Interest?

Back_at_it

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I'd be onboard for a simple GPS tracker that I can use from my phone. I don't care about telemetry as I have an altimeter that works amazingly well and is tiny.

I'm looking for something that could fit inside a BT50 sized tube. While I typically fly larger rockets, it's the smaller stuff that I normally lose up at BONG Rec area due to the over grown brush. But then again I did lose something the size of a Super Big Bertha last year :(

If you could produce something like this and get it to market under $100 I think you would have a winner.
 

QFactor

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What do you propose for the user's handheld device for locating the rocket? Stand-alone base unit or a linkup to a smart phone?
 

Hyak

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Nothing I can Add to what has already been written except to say that I would be very interested as well! I dont fly a lot of 18mm airframes, but really small tracker would be great to have at $100<, and better $50<

Let us know!
 

mh9162013

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I'd be interested in this. But like at least one other person has mentioned, I wouldn't need the telemetry. I just want something that'll help me find a lost rocket.

I just want something small that'll fit in a BT-50 sized LPR that will serve as a "homing beacon" for a reasonably priced handheld device that I can have with me during the launches.
 

jimduchek

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I'd be interested in this. But like at least one other person has mentioned, I wouldn't need the telemetry. I just want something that'll help me find a lost rocket.
Finding a lost rocket was the initial goal of the whole thing, but if you're gonna put some electronics on the bird, might as well get some extras out of it, right? I'm packing what I can into a 14.5mm-wide board (I determined I can stack two 14.5mm boards at like... 1.5mm apart? Have the specs of the connector I picked somewhere) and still fit into an 3d-printed 18mm nose cone w/1.2mm walls, so that's my width limit). You'll be absolutely fine w/BT-50. Length is around 27mm at this point, but not yet fixed.

So, status updates for those who are interested. Haven't got any days with low enough wind to actually fly with my test unit, grr. And most of the week been working at the Real Job, but still, made a lot of progress. Established 2-way communications (sending commands to the rocket in addition to receiving a downlink). Started cleaning up code and trying to do a little documentation (I always wait til the end when I should be doing it as I go!). Good work going on the app (see attached). I love the look of that gauges library I found but I'm gonna need to do some work on it cause it's missing some stuff (like captions!). Established comms to send commands from the app to the rocket, so that's cool (right now it's just turning power to the GPS on and off -- the idea is that the rocket electronics will stay super-low power until put into 'flight mode' where it will turn up the GPS and start sending data quicker). I've got a 1000 mAh battery on my test setup... but I think I'm going to ship with a 80 or 50 mAh battery, so that kinda stuff is key. I'm shooting for 4 hours of 'low power' battery life, and maybe 30 minutes of "flight mode" battery life. The board will have an accelerometer so it'll be able to kick back to low power once it knows it's landed/sitting still, and then just keep saying "hi" every 10-15 seconds until you pick it up.

Think I may be settled on the ATSAMR34 processor, have a dev kit arriving (tomorrow, if the USPS website don't lie) so I can make the final decision. I haven't spun up a board in a couple years and, so I'm incredibly frustrated by the shortages of _everything_. Think I'm looking now more towards about $30-$35 for the base board and $25-$35 for the GPS daughterboard. Sucks, because I really wanted to be able to sell a base+GPS unit for <$50. But I'm picking parts (even down to stuff like USB connectors) based on what I can find that somebody actually _has_ a couple thousand of, and that means I'm picking some parts that are overpriced. There's so many parts that are active/"stocking" but 0-in-stock and "available: 2023".

Unless I'm missing something, it doesn't look like there's an option to do "polls"/"surveys" on this board. Think I might set something up off-board. Curious what people think/want about a few things (For example -- the board will have a USB connector for charging/programming. Should it be micro-USB or USB-C?)
 

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mh9162013

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Finding a lost rocket was the initial goal of the whole thing, but if you're gonna put some electronics on the bird, might as well get some extras out of it, right?

Yes and no. For some users, the added features would be great. For others, not as much...or at least not worth the added cost (and weight) for the product.

Oh, and USB-C all the way. USB-A/B/Micro/Mini are dying "formats."
 

QFactor

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Yes and no. For some users, the added features would be great. For others, not as much...or at least not worth the added cost (and weight) for the product.

Oh, and USB-C all the way. USB-A/B/Micro/Mini are dying "formats."

Nothing dies, it just adapt(er)s.

3679-03.jpg 4715-06.jpg 4715-04.jpg

RCA is still with us and thriving . . . .
 

mh9162013

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Nothing dies, it just adapt(er)s.

View attachment 516512 View attachment 516513 View attachment 516514

RCA is still with us and thriving . . . .

I'm fairly new to the model rocketry hobby, so I don't know if it makes more marketing and financial sense to have newer formats and ask "holdouts" to get an adapter or to use an older format and ask the "newest and greatest group" to use an adapter instead.

But my gut says it's better to use the newer format in the product and ask those using older formats to get an adapter instead of the other way around. I could be wrong, though.
 

jimduchek

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Yes and no. For some users, the added features would be great. For others, not as much...or at least not worth the added cost (and weight) for the product.
That's why I'm moving GPS to a daughterboard. It's definitely extra-pricey.

Oh, and USB-C all the way. USB-A/B/Micro/Mini are dying "formats."
You know, that's been sort of my thinking lately BUT... I am working on the app on an old Note 5 (w/micro-USB) that I have instead of any of my newest phone w/USB-C. Why? Because the USB-C connector already died on it in less than a year (has wireless charging, so it's fine for daily use, but can't plug in an OTG cable to the transciever...). I thought USB-C was supposed to be more rugged, but in my experience, it has not been. Last phone did the same.

Did you state a specific weight for this device?
Maybe 15-20g w/the GPS add-on. I don't actually have any of the batteries as small as I plan to use to actually weigh it, but seems a 80 mAh battery weighs less than 5g... hard to find accurate info there in the datasheets, a lot of widely varying values. A 4 layer board of the size I'm currently working with is ~2.5g, so double that, though the GPS board will be smaller and probably only 2-layer... Using a spiral copper LoRA antenna that probably adds a couple g there. SD card, usb port will have some heft to them, and a GPS module definitely does. Very much doubt it will clear 25, but we'll see.
 

jimduchek

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Oh, and also, the weight (per my previous post) might get up above 30g. I forgot that lithium batteries only can run about 1C (ie, a 100mAH battery can only produce about 100mA of current). So while an 80mAH battery has more than enough _capacity_ for what I'm doing, it can't produce enough current. In full form this board might draw up to 200-250 mA (GPS on, LoRA blasting as hard as it can), so a 250-300 mAH battery is going to be necessary. Though since it will have an accelerometer, it won't be spending that energy hardly ever... but it needs to be able to do so for the minute or so it's in flight.
 

Grant_Edwards

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Oh, and also, the weight (per my previous post) might get up above 30g. I forgot that lithium batteries only can run about 1C

The discharge rate for Lithium batteries varies tremendously check the specs for the specific battery. I have Lithium batteriis that are rated for 40C peak 20C continuous discharge.
 

jimduchek

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Thanks everybody! Only 16 replies on the survey so far but most of the things I really wanted to know are swinging pretty hard in one direction. And in each case, the way I was leaning anyway, so... That works. The only real thing that changes is that it seems most people aren't going to want to modify their stuff and would prefer switches. But I don't think there will be any. On the "expected modifications" front:

A). I'm putting the pressure/temp sensor and the accelerometer on a snap-off portion. There will be two JST connectors, so you can snap the sensors off and move them elsewhere by making/buying a cable. (A 6 pin 2mm JST cable is available in a zillion lengths pretty easy, if you can't make) This is because the temp/pressure sensors won't give good data in a sealed-ish compartment. Can use the connectors to tap into the i2c bus too if you're hacking at it.
B) The board will have a physical power switch that disconnects the battery. I'll be using a thru-hole part for the switch so you can desolder the switch and locate it elsewhere if you've got a bigger diameter rocket and the board is a little buried. If I have room, I might just add holes to add a switch without desoldering the old one, but I don't think I'll have it.
C) I'm using a spiral wound antenna soldered to the board for the LoRA antenna (cheap... And will get the job done for most of you). It will also have a u.fl connector for a bigger/better antenna. RF capable physical switches get pricey and there's not much available, so if you want to use an external antenna, you'll need to desolder the spiral. But I THINK you will be able to just snip it off with wire clippers with little signal degredation, which should be a doable option for almost anybody.


Also it seems those of you with interest are 50/50 on having a 3d printer. So I think I'm going to need to prepare SOME sort of options for people to score nose cones for this thing. I have no interest in using my own printer in a commercial capacity, but I'll try to make sure there's some easy way y'all can get some parts to fly with this. Probably just verifying some designs with one of the online printing houses that you would be able to order from them.
 

jimduchek

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The discharge rate for Lithium batteries varies tremendously check the specs for the specific battery. I have Lithium batteriis that are rated for 40C peak 20C continuous discharge.
Hmm. My house runs on LFP batteries and I kinda just assumed the little ones are the same way. This is good news. I picked up an 80mAh battery and holy hell it's tiny - if it can produce 300 mA for a while without issue that's awesome. The survey says that's more than enough for most folks, almost nobody wanted more than an hour of standby. And I'm estimating around 20 mA (average) on standby and around 200 mA in "flight mode"
 
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Jim, thanks for your efforts!

Survey is filled in, besides that I can just repeat what some others already said:
Telemetry would not be of my first preference as I already own a Altimeter 2.
A small, light and affordable tracking device for my LPR stuff would be great, as a composite D9 is well enough to get in difficulties spotting the rocket.
I am really not into electronics, but googling a bit indicates to me that LoRa would be sufficient, preventing additional cost for GPS services.

Look forward to hearing on the progress of this!
 

jimduchek

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Hi all, sorry for no recent updates. I finally got a day to fly some of my test code and it didn't go so great. Or I guess, I got perfect signal the whole time as the dang thing landed 100 feet away and no tracking was necessary, but i knew where it was on my phone! :D Was not happy with my code as it didn't work/log everything I wanted it to. And I couldn't get the engine out of my 3d-printed ass-end so I only got to launch it once.

With that said, here's a couple things:
Anybody willing to launch and test some code with off-the-shelf hardware? The big problem is that the first test unit I chose (a T-Beam) is real long and heavy. But PM me if you've got some capability to print a shell and play with it. Would like to get more launches under the belt of the software, even if it's not my hardware on the backside.
I've been super busy with Real Work here lately but I'm about to finalize the design and get a few boards printed up to play with. Assuming I didn't majorly f* anything up and they're usable... Anybody in the US who has some basic electronics experience and also launches pretty regular, send me a PM.
 

jimduchek

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Continued update: This thing ain't dead. I've just been super busy with other things. Despite other parts of the pandemic mess loosening up recently (gas prices coming down, etc -- please no politics here, regardless of causes, reality is reality), the chip shortage is showing no signs of letting up. A couple parts I intended to use 2 months ago... are no longer available. Very frustrating because I'm at the point I'd like to spin a couple boards for testing but I can't trust the same parts will be available a month later for a production run. We'll see though. Hoping to have some boards in my hands (and hopefully, to some intrepid testers too) in mid/late-August.
 

BEC

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Just did the survey. The Flightsketch SST, which is in development but hamstrung by "the supply chain" is probably the product yours would be competing against, at least from my knothole.

I also just realized that when I fly at sites where I might actually need a tracker, I probably fly motors bigger than C impulse (which is what I put in the survey) but I do prefer small and light rather than large chunks of plywood, fiberglass and steel hardware. A possible use case for your proposed device would be flying something like an Estes Star Orbiter on a full F or low G, or putting a smaller model, like my favorite Nova Payloader up on a full D (so to ~1700 feet). Either of these are likely to be out of sight at apogee under anything other than ideal sky conditions.....

Very interesting......

Oh, one other thought. Telemetry, per se, is very low priority for me (except perhaps position and maybe altitude). I have a TeleMini, but I've only flown it a few times. But good data logging and means of good GPS location so I can find it after it disappears in the sky — that is very attractive to me.
 

shockie

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I think this and the FS SST are great ideas.

Finding launch sites is becoming increasingly difficult and having GPS in lpr-mpr rockets is needed.

Now if somebody would just make me a jolly-logic for a bt-20
 
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