# Smallest size electronics payload ever!?

## What's the smallest dia. rocket you want to use electronics in? (alt, timer, tracker)

• ### 54mm

Results are only viewable after voting.

#### FROB

##### Well-Known Member
Yes, folks, this is yet another poll, though there is purpose to this, if you vote and i hope you do, and even better if you post a detailed explanation of your preference, you could be richly rewarded! *
* (1 free rocket electronics draw for all participants who comment)

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#### Meat

##### Well-Known Member
I am still pretty new to all of this so my comments wont really help a whole lot but I think its great subject .

#### jj94

##### Well-Known Member
I chose 38mm, but I should have done 18 or 24. At first I thought you meant what diameter rocket you would want it in. I chose 38mm cause it's closest to a BT-60. Then I realized you meant motor diameter. I'm a bit slow today. I have some 18/24mm rockets that I wouldn't mind putting an altimeter in.

#### Microspeed

##### Well-Known Member
I picked 13mm. If you could get enough functionality out of a 13mm board (at least altitude recording, perhaps/preferably a timing--deployment/airstart/etc. output, or more, it could be used in almost anything bigger. Plus, there are plenty of boards out there for the 24mm size and up that have deployment capabilities (PerfectFlite, G-Wiz, and up), and 18mm boards that will do recording (PerfectFlite). I thought I remember there once being a 13mm recording altimeter, but I haven't seen anything about it recently, but it would be a lot of fun to have something to put in those micro scale models (oh, the staging, clustering, airstarting, strap-on-ing possibilities...).

#### FROB

##### Well-Known Member
Hi Josh,
Actually you're not as slow as you think- were right the first time!

To clarify, the dimension in the poll refers to what size body tube the circuit has to fit into - in reality, it would be slightly smaller to get into a typical coupler with some clearance for tall components.
I assume though that is most critical in minimum-diameter rockets, where motor and body tube size is the same- that's why i used typical motor sizes.

In any case if the body tube diameter you would use doesn't correspond to any of those listed, please give the exact size (like BT-60) in your comments.

Thanks!!

#### brianc

##### Well-Known Member
I selected 13mm, but only because you omitted the MMX sizes...

#### FROB

##### Well-Known Member
MMX eh?.... thats 6mm - not easy .... wait..maybe if....
well, i suppose it could be done, but what about power? i don't know of any batteries that would fit! how would you power it?? it needs 3 volts.

If you're serious, well i could probably shrink my 13mm design just to claim the record.
Let's see...Barometer, 1 or 2 led's, 1 pushbutton, no room for a buzzer. Altitude read out by led's. I don't suppose you need this to work up to 100,000 feet? Could be certified for TARC use though.

One Pyro output? do you really need it? that means you have to fit another battery somewhere with enough juice to light an igniter - solve that and I'll ad it in there.
Homemade xmass light igniters work with as little as 50mA @ 3v, but that wont fit in the nozzle.

Maybe you could sign me up 25 people who want one with say a $10 refundable deposit? I figure it would cost ~$50 ea. Probably less but not more.
If anyone really wants something just for mmx size, send me a pm - if i get enough interest, consider it done.

I picked 13mm. If you could get enough functionality out of a 13mm board (at least altitude recording, perhaps/preferably a timing--deployment/airstart/etc. output, or more, it could be used in almost anything bigger. Plus, there are plenty of boards out there for the 24mm size and up that have deployment capabilities (PerfectFlite, G-Wiz, and up), and 18mm boards that will do recording (PerfectFlite). I thought I remember there once being a 13mm recording altimeter, but I haven't seen anything about it recently, but it would be a lot of fun to have something to put in those micro scale models (oh, the staging, clustering, airstarting, strap-on-ing possibilities...).
Then there's the Parrot altimeter, which has barometric and accelerometer recording and 3 programmable outputs, fits in an 18mm tube and only weighs about 9 grams. To get it to fit in an 18mm tube, you need to order the version without the output screw terminal block, or get it with the screw terminal block and then sand off the corners.

I have a prototype baro-recording-only altimeter that will fit in a 13mm tube, but I put the development for it on hold. It may get restarted, though.

#### FROB

##### Well-Known Member
...So now that we've both given your product a plug, as a rocket builder and flyer, would care to share which way you vote on the poll and why?

#### MarkII

##### Well-Known Member
I think that the Pico timer might fit into a Micromaxx body tube. I'm not sure what is required to power it, though. Some of my wife's quartz wristwatches have movements that would fit into a 10.5 mm (BT-3) tube, and possibly into a MMX tube. Someone with a little ingenuity (not me) might be able to adapt such a movement to perform some flight event, such as staging...

... or dual deploy...

Mark \\.

#### georgegassaway

Said 13mm.

Mainly thinking timer.

But if the LIGHTEST option was to do it for 18mm, then I would go for 18mm. some of the applications I might have a small timer for would tend to be more critical for the mass rather than the size, at least if it could fit into an 18mm tube.

I realize that at some point it gets to be more about the power source (battery) than the circuit board. Flexibility in power source is good too. So that the flier could try some smaller and lighter battery, with soldered wires, than be forced to use a specific battery in a specific holder mounted to the board (unless it was one heck of a small light battery). It would be fine for the timer to use a battery holder for the majority of those who would use it, just leave it possible and not TOO hard for modelers to delete the holder and wire in a lighter battery. Unless it was powered by a really small battery like a 8/10 gram watch battery, obtained form opening up a 12V &#8220;N&#8221; sized alkaline battery that has 8 cells inside of it. I actually have a Zitnan timer from Slovakia powered by one of those cells, but it was built-to-order for a specific duration, not adjustable, and I do not think it is made anymore).

There used to be ultra-low current e-matches available. The Daveyfire NB-28L, I think it was called, the above timer worked with those, but they are &#8220;unobtainable&#8221; now. These days, maybe the most practical low current ignitor is the new Quest ignitors that sometimes are set off by systems that have too much current draw on continuity check? Those might be a good baseline to shoot for. Hmmm, perhaps I should try that Slovakian timer with one of those Quest ignitors and see if it&#8217;ll fire one. Do not know if I have any of the battery cells to test with though.

Photo below, that Zitnan timer I mentioned. Created for "dethermalizers" for FAI Rockets and FAI Boost Gliders. The 4:19 meant that it would fire 4 minutes and 19 secs after the shorted SIP socket was pulled. That allowed time to manually start it before launch, count down, then 4 minutes to fly before the "max" duration was achieved, then set off and make the model descend quickly.

- George Gassaway

#### rokitflite

##### Well-Known Member
I voted 13mm... Cuz' if it fits in 13mm it will fit in everthing else larger!

...So now that we've both given your product a plug, as a rocket builder and flyer, would care to share which way you vote on the poll and why?
I voted for 18mm because it's the smallest size into which you can fit a full-featured altimeter, but on second thought I should have voted for 13mm because if I had a bare-bones 13mm altimeter I would use it for my club's A altitude record.

#### henry8minus1

##### Well-Known Member
I voted 24mm, though now that I reconsider I think 18mm should have been my vote, but either way I doubt I would need it smaller than 24mm very often.

#### Micromeister

##### Micro Craftman/ClusterNut
TRF Supporter
Ah HMMMMM!!!! you missed a couple models sizes!!!

I have and used a micro altimeter that fits nicely with it's supercaps in a 10.5mm model body
and staging timers that work will in .281" and .316" (T2+ and T2++) size body tubes

As batteries packages and Supercaps get smaller these items i'm sure will also go down in size

#### FROB

##### Well-Known Member
Ah HMMMMM!!!! you missed a couple models sizes!!!

I have and used a micro altimeter that fits nicely with it's supercaps in a 10.5mm model body
and staging timers that work will in .281" and .316" (T2+ and T2++) size body tubes

As batteries packages and Supercaps get smaller these items i'm sure will also go down in size
Hey thats awesome! - do you sell these ?
can you share anything more about the design? - or how you power them? I know nothing about Micromaxx- what igniter's or e-matches can you use and with what power source to get something that small to work reliably?
You mentioned supercaps - but i haven't found anything smaller than 8mm dia.(0.314) that has enough capacity and low enough ESR. Same for batteries.

Are those common MMX body tube sizes? sorry for all the questions, I've become very curious since you guys bought up MMX- that's an all new topic to me.

TRF Supporter

#### MarkII

##### Well-Known Member
Minimum-diameter Micromaxx tubing (like FlisKits BT-2.5 or ASP T-MM) has an OD of 0.281" or 0.282". BT-3, or T-10.5, is also commonly used in Micromaxx model construction.

I have heard of using super-capacitors to fire igniters in staging or air-starts, but I have never heard of them being used to power on-board avionics. Smaller super-caps could probably fit into a BT-3 tube. Micromeister will probably provide much more info.

I am quite surprised to see electronics used to stage MMX motors; it is something that I have been thinking (and dreaming) about for the past 4 years. I figured on using the PicoAlt micro-timer, but I wasn't sure if it would be wise to put an electronics package that was even as inexpensive as that one into a micro model. A combination of my lack of knowledge of electronics and my lack of financial resources has prevented me from pursuing the idea since then. Those with deeper pockets than my admittedly quite shallow ones have apparently been able to follow up on the idea, though.

Mark \\.

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#### FROB

##### Well-Known Member
Doh! now i remember....thanks for the reminder.

#### FROB

##### Well-Known Member
...I am quite surprised to see electronics used to stage MMX motors; it is something that I have been thinking (and dreaming) about for the past 4 years....
I didn't expect that either. how high can these things go anyway?
As far as staging, i think the 'chad' method easier, certainly lighter, and a lot cheaper, if not quite as reliable- with engines less than \$1 ea, you can keep trying till it works perfectly. Is that not possible? Or does the new MICRO MAXX NE engines solve that?

I would imagine, these things being so small, that its quite easy to loose them outdoors in tall grass etc. If that's the case, a tiny beeper or flashing LED might be more useful. Do you agree?

I think it would be possible to make a tiny altimeter to fit inside BT-2.5 powered by a tiny supercap. It wouldn't hold enough power to reliably light an igniter, but it could power the altimeter for the flight and allow it to store its data to eeprom. In a BT-3 model, you can stack 2 or 3 watch batteries to power the thing instead, so it can keep going and flash a bright LED as a visual locating beacon after the flight, giving the altitude as a flashing pattern.

to keep cost down, it could detect launch when an external battery connection is broken:
There could be 2 tiny, low-friction pin sockets on the edge of the board that you'd line up with 2 tiny holes in the side of the airframe, so you can poke in a power "umbilical" of 24AWG solid wire from a pair of alkaline cells that stay on the ground near the pad. That would also charge the supercap.

Or for a few bucks more i can have a tiny 8G 3D accelerometer detect launch, and also log its data during the flight. That has some other benefits too, since it can act as user input device to program it.
That also might be handy to detect burn-out for use in staging. In that case you'd probably be limited to BT-3 size to hold a big enough supercap to do the job, with the lowest current igniters such as Q2G2.

I'd probably sell it as a kit with a couple of different size supecaps & battery clips that you can change depending on what you're doing.

How does that sound?

Hmm... it 'd be interesting to be able to do some a micro-scale models like a Delta III or Delta IV-heavy, with working drop-off boosters, eh?
Now i have to get some MMX igniters and run some tests....

#### bobkrech

##### Well-Known Member
Robert deHate's 13 mm carbon fiber 2-stager using his PiocoAlt electronics.

The entire rocket with electronics and recovery systems weighs 28.1 grams (0.99 ounces) without the (2) A10 engines.

The staging electronics bay weighs 8.8 grams.

The sustainer altimeter bay weighs 3.5 grams.

https://www.geocities.com/rdh82000/13mmTwoStage/Construction.htm

Bob K.

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#### FROB

##### Well-Known Member
Yeah, that's an amazing project.
Robert if you're in here, what supercap & batteries did you use?
Out of curiosity, how high has it gone?

#### rdh8

##### Well-Known Member
Yeah, that's an amazing project.
Robert if you're in here, what supercap & batteries did you use?
Out of curiosity, how high has it gone?
The model Bob posted uses a 1F super cap for the staging timer and a 1.2V NiCD battery for the altimeter.

Super cap:
https://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=283-2776-ND

Robert

PS: I have not flown the two stage, I am too chicken....I mean I am still developing the composite motors for it.....

#### FROB

##### Well-Known Member
Yeah thats the same one i was looking at. What kind of testing have you done using the supercap to fire ematches/igniters? which igniters did you use? how reliable is it?

...I mean I am still developing the composite motors for it.....
You mean like these? : https://www.gmarocketry.com/13mm_Research_Hardware.html
That might give you a head start there....

#### DexterLB

##### Well-Known Member
I selected 18mm.
Actually, at the moment I am constructing a timer which will fit in an 18mm rocket.

#### Threemorewishes

##### Well-Known Member
I voted for 24mm. I would want an LCD readout on a two pyro event (dual deployment) 24mm able device. Recording the flight data would be nice but altitude is the main concern at the moment.

#### kramer714

##### Well-Known Member
29mm is my choice, but...

Using the altimeter for dual deploy, my problem is the wires and connections sometimes add significantly to the size of a bay I need. If the altimeter had a plug on it that I could make a wire harness that plugged in, it would save weight, and eliminate the chance that screw terminals would come loose or break.

It would also make swapping electronics simpler from rocket to rocket.

#### FROB

##### Well-Known Member
Thanks for all the replies so far- keep 'em coming!

Ok so so far, the sizes picked are pretty even across the board.
I wasn't expecting that at all!
Especially on the low end of the scale, it's interesting to see there looks to be real interest in the very tiny 13mm and below sizes.

SO what does this all mean?

Not sure, but it has helped me tremendously to decide on the form factors I'd try to target no matter what gadget i decide to make:

1- Micro-scale- i don't know it its the economy, but there seems to be an explosion in interest in micro-maxx and midget sizes from BT-2 to BT-20.
Thats cool- and so a line of very low cost and tiny "flea-size" devices might be worth doing.
I think there's a lot of functions that can be crammed into really tiny boards that might fit in a BT-2.5 .
- or a "typical" full-featured device that fits in a BT-3 (8-1/2mm) or BT-4 (10-1/2mm).
I'll look into that.

2- For real advanced stuff like telemetry, GPS, video etc., I'm thinking that 29mm should be the optimum size to target, from your votes, and because there are clearly motors available that can take a min-dia rocket this size to over 10,000 feet, with a few people doing occasional record attempts at this size.
I can pretty much make anything fit in 29mm, without too many compromises in terms of connectors and features.
I was on the fence about trying to target 24mm, but even with the new AT 24/60 'F' motor i just don't imagine there's be many people wanting to do a min-dia. screamer that size (with telemetry etc.), and i can use the extra space so that the 29mm version would be shorter in length and significantly easier to make & use.
Of course, i reserve the right to change my mind. (especially if there is a significant amount of prodding to do so)
Another thing i'm thinking about doing is a square form factor that will fit on a 75mm bulk plate- and then constrain all the circuitry and parts in a 54mm circle (user can trim the board to that line).
That should appeal to anyone doing high-performance minimum dia. stuff at those two sizes or larger.
It might even be possible to do something like that at 38mm but with some features removed. Any opinions on that folks?

3-In much larger sizes, it seems there would be less need for telemetry/ GPS etc- even an 'M' motor in a 12" airframe for example will only get to a few thousand feet, and be easily visible the whole time.
And there's plenty of altimeters and such on the market already that are suitable for larger airframes.

#### FROB

##### Well-Known Member
Ok here's a little teaser for the MMX crowd:

i just got the last of the component samples that i was waiting on, for the smallest device i want to do.
I couldn't resist lining up all the key parts on top of a quarter with a ruler to take a picture and show you just how small this can go.
The first picture i tried to include my thumb for scale but hard to hold the camera with one hand and push the trigger so its a little fuzzy.

To the left of the quarter is typical "miniature" pressure sensor
and on the right is a precision digital gyroscope chip i will use later.

On the quarter from left to right is my barometric sensor, the CPU, the 3-axis accelerometer (g-switch), and finally the dual 8-Amp mosfet for pyro outputs.
of course, there's a few other little parts needed, but those will mostly be R's & C's only 1/2mm wide.
The largest part, the pressure sensor, is 5x5mm. the whole board can therefore be as little as 6mm wide and if so, it will need to be about an inch long. I have decided on using 2 tiny watch batteries for that in a unusual mounting arrangement that will allow the whole thing to still fit in a 1/4" tube, adding only another 1/2" in length.
That will still fire low-current ematches if you add a small supercap, which would add another 1" in length and increase the diameter to a whopping 8mm.
Without the supercap it should weight on the order of 1 gram

Cool, eh?

Now i can't wait to get the board design finished and assembled.

#### abw

##### Well-Known Member
Does anyone know what the maximum functioning altitude is for the PicoAlt altimeters? I was discussing putting an altimeter on some high-altitude balloons in another thread, that reach maximum altitudes of about 130,000 ft...