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spudgun range, are we falling short?

A place to ask general spud cannon related questions.
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Unread postAuthor: MrCrowley » Wed Apr 25, 2012 5:06 pm

POLAND_SPUD wrote:but he's a fuc#### native speaker for god's sake
I would say I'm reasonably intelligent and my reading and writing skills have always been above average but I still screw it up sometimes :wink:

I think I've mentioned this before where I've said that Europeans who are fluent in English will probably know the rules and grammar better than a native speaker but will fall short on things like pronunciation and vocabulary. When trying to learn German, I probably learned more rules and grammar about German than I knew about English. We get taught what a verb, adjective and noun is but I don't remember once ever being tested on them. We focus on analysing poems in English classes, not the theory of English as if you were actually learning the language.

I remember an ex of mine, who was German, corrected me on something I just knew was right; turns out she was right. I was right in the sense that what I was saying is a far more common phrase in NZ even if it wasn't the grammatically correct way to say it.



Back on-topic:

If we did go with the RF route, can you glue the antenna to the fins of the projectile as a way of increasing the antenna length? Kind of like this:
Image


Edit:

Some interesting projects here:
http://www.ausrocketry.com/forum/viewforum.php?f=32
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Unread postAuthor: jackssmirkingrevenge » Wed Apr 25, 2012 8:01 pm

I picture POLAND_SPUD in a vest with a half full bottle of polish vodka shouting his posts in a thick accent as he types them, and it all makes perfect sense :D

Here is a little information on the reasons for a "softer" potting compound.
You can do what you want but there are reasons for why I stated what I did about "hard" epoxies.


I see what you mean, but at the same time this stuff seems more geared towards vibration and thermal shock, as opposed to the violent acceleration while being shout out of a cannon. Don't you think being subjected to tens of thousands of g would require something harder?

If we did go with the RF route, can you glue the antenna to the fins of the projectile as a way of increasing the antenna length?


Maybe Dewey can chime in, there's certainly many opportunities to coil a longer antenna. One of the specific tests I want to do with the kid tracker tags is bury it and see how that affects range.



oh yes :D
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Unread postAuthor: POLAND_SPUD » Wed Apr 25, 2012 10:31 pm

Look what I found -> http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA443252

They even mention g-hardening of electronics used in smart artillery rounds... it seems that softer compounds are the way to go >
There is a wide variety of
potting materials to choose from, ranging from room temperature vulcanizing rubber to
urethanes to lightweight structural foams.




That is OK, PS can not even edit the the quote without a spelling error!
lol

I picture POLAND_SPUD in a vest with a half full bottle of polish vodka shouting his posts in a thick accent as he types them, and it all makes perfect sense
I think my accent isn't that bad

Anyway... Must not get drunk and post stupid stuff
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Unread postAuthor: jackssmirkingrevenge » Wed Apr 25, 2012 11:58 pm

POLAND_SPUD wrote:Look what I found -> http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA443252


Interesting!

Dropped consumer electronic
devices can be subjected to accelerations from 400 g’s to 4,000 g’s


There you go MrC ;)

The report refers to the SADARM.

This wasn't what I was looking for *sigh* but mmm.... *ahem* anyway.

If they can fire this sophisticated bit of kit at several times the speed of sound, I think we can manage a RF tracker:

Image

I don't see why marine epoxy wouldn't do the trick - it will hold the components very rigidly, which is what is required. It might be more brittle than urethanes but this will be catered for by the foam packing. In any case, before I have the tag in hand I can't really decide which is the best way to go. According to the postal tracking the item has arrived in epoxyland so I should have it any day now :)

I think my accent isn't that bad


I'm sure it isn't, but I note you didn't object to any of my other assertions hehehe

Anyway... Must not get drunk and post stupid stuff


I'm not holding my breath :D
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Unread postAuthor: dewey-1 » Thu Apr 26, 2012 9:01 am

jackssmirkingrevenge wrote:Dewey, what's the best strategy - antenna in a synthetic body, or metal body hooked up to the antenna?


Probably the nonmetallic body due to the simplicity of using a coiled or straight lead antenna whether it is internal or external.

There are so many different possible ways to make an external antenna work on a metallic body but the problem is each would need a coax feed line and then tests to see if desired results are obtained. This is best done by those with experience in RF circuits. I looked at the spec sheet and saw that it is a 2.4GHz system. This limits the antenna modifications allowed.

We can discuss options later. Good closeup overhead pictures of the tag both assembled and completely disassembled.

Closeup overhead pictures of the tag PCB top and bottom will allow me to create a schematic.

Do some range testing with the existing antenna as a baseline test.

Then you can do range comparison between the modified tag and the "stock" tag.

Do not do any potting until after the range tests of the tag inside a projectile.
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Unread postAuthor: jackssmirkingrevenge » Thu Apr 26, 2012 10:05 am

Excellent, many tests to be done!

I will probably have this in hand on Monday, watch this space :)
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Unread postAuthor: jackssmirkingrevenge » Wed May 02, 2012 1:51 am

I has tags!!!

but booooo! I thought I was getting this but in fact I got this, which means shorter range and less precisely indicated search mode, and just one tag instead of two.

Still, it will do for experiments. Tried switching them on and one of them got really panicky until I put the other right next to it, awwww...

Image

I'll have a play when I get home, keep watching this space :)
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Unread postAuthor: dewey-1 » Wed May 02, 2012 8:03 am

Now remember, the blue one is the tag. :D

They sure are difficult to tell apart from each other.

Looks like the range is the same.

Here is an article for a 2.4GHz Yagi antenna.

http://www.ab9il.net/wlan-projects/wifi6.html

Premade antenna;
http://www.ebay.com/itm/2-4GHz-20dBi-Ya ... 5649ee8e06
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Unread postAuthor: POLAND_SPUD » Wed May 02, 2012 12:47 pm

here is something I found out (not sure if it's useful for this thread but I'll post it anyway ;-) )

so... I've been playing with 5308IRC-10 IR LED diode and TSOP1736 IR receiver and they've got amazing range... plus the IR receiver can sense IR signals reflected from objects even 3-4 meters away... I concluded that's way more than what you an get from real IR based range finders and I guess it could be used for:
A) sensing ground (though I realize one would need a fast acting release mechanism for paint or whatever you want to use)
B) sensor fuzed munition (like bofors 3P ) :wink:
C) proximity fuze
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Unread postAuthor: jackssmirkingrevenge » Wed May 02, 2012 12:51 pm

dewey-1 wrote:Now remember, the blue one is the tag. :D

They sure are difficult to tell apart from each other.


HAHAHAHAHHAHAHAHAHA!

It would be extremely "JSR"to fire off the receiver by mistake :D :D :D

Looks like the range is the same.



Interesting! going to have a play with the unit soon :)

POLAND, you're starting down a dangerous route ;)
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Unread postAuthor: POLAND_SPUD » Wed May 02, 2012 1:22 pm

POLAND, you're starting down a dangerous route
I don't really get what you mean ?

no I don't really mean explosives, though I have to admit they would be the best for this purpose

if you think of it you might as well put an ATtine IC on the projectile and program it before launch (for example to deploy a parachute after X seconds etc. )

technology is already here and it's quite cheap (3-4$ for an ATtiny chip)
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Unread postAuthor: jackssmirkingrevenge » Wed May 02, 2012 5:02 pm

POLAND_SPUD wrote:if you think of it you might as well put an ATtine IC on the projectile and program it before launch (for example to deploy a parachute after X seconds etc. )

technology is already here and it's quite cheap (3-4$ for an ATtiny chip)


Something that would burst into highly visible and non-penetrating fragments just before it hit the ground would certainly be useful.

As to the tags, been having a play and I'm quite disappointed so far. Either they're not so good, or I'm not using them correctly. And the cricket noises are driving me mental, I'm hearing them when the things are off too!

There certainly is some discrepancy with what the manual says, it claims a green LED on the base unit will light when it's pointed in the right direction, but it hasn't gone green once, even when the tag is in close proximity. There were occasions when I put the tag one end of the driveway and it did light up brighter and beep when it was pointed in the general direction of the thing, but it was doing that for other directions as well. Maybe an urban environment is too cluttered with wifi, who knows.

Something for the electronically minded, can I replace the button cells with an AA battery pack without blowing it up?

edit: d'oh manual link
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Unread postAuthor: dewey-1 » Wed May 02, 2012 5:33 pm

Yes you can.

The CR2032 is 3 volts, so use 2 AA alkaline cells in series.
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Unread postAuthor: Fnord » Wed May 02, 2012 5:49 pm

<strike>It won't blow up if you use the same voltage as the button cells put out.
If they're stacked up they're in series, so the voltage will add up linearly. Use AAs in series until you get the same voltage.</strike> ninja'd by dewey.

Anyway, if you want a 2.4ghz antenna, you can always make a cheap one out of a pringles can, (or "cantenna"; look it up).
If you want something not-so-directional, make a biquad or double biquad.
I've made a few of them and they're quite easy, have high gain and a wide-field horizontal radiation diagram. You'll need to use proper coax cable/connectors rather than just clipping some wire on, unfortunately. Gigahertz-range transmissions are very intolerant of interference.
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Unread postAuthor: jackssmirkingrevenge » Thu May 03, 2012 12:01 am

Cheers for the tips guys. Before making/purchasing a separate antenna though, I want to confirm these things work as they're meant to without modification.

Dewey suggested the units might be too close together, I did some longer range experiments and again, nothing conclusive. On several occasions the base unit did show considerable enthusiasm when pointed in the general direction of the tag, but did so in one or two other directions too, sometimes completely opposite :?

Feels like this:-/
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