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spudgun range, are we falling short?

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Unread postAuthor: dewey-1 » Sun Apr 22, 2012 3:06 pm

Here is the conformal coating I have used in the past on circuit board assemblies for production use. Dow Corning 1-2577.

http://www.dowcorning.com/applications/ ... DCCSF=21EN

See if you can get an "Engineering Sample" through your chemical suppliers.
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 22, 2012 3:12 pm

Isn't a hard epoxy a better idea to make it resilient to shock? My idea would be to encase the board in epoxy, then have this epoxy capsule surrounded by a softer material (rubber, foam etc.)
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Unread postAuthor: Labtecpower » Sun Apr 22, 2012 3:23 pm

for shock dampening I'd suggest using tempur foam, it's amazing what this stuff can do.
egg dropped from 2 meters will survive if it lands on a 3 cm thick piece
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 22, 2012 3:29 pm

Labtecpower wrote:for shock dampening I'd suggest using tempur foam, it's amazing what this stuff can do.


I still have something like this design in mind, that stuff might be a good filler :)

edit: went ahead and ordered some memory foam insoles I can punch disks out of :)

MrC, do you think the projectile would have trouble getting through customs, obviously projectile shaped and with circuitry in the middle?
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Unread postAuthor: MrCrowley » Sun Apr 22, 2012 3:42 pm

I would be quite surprised if there was an issue with customs. I don't think one of the officers would be able to see the projectile and think that it was anything but a toy. Anyway, unless you're trying to sneak fruit or drugs in, they probably don't care :P
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 22, 2012 3:51 pm

Cool :) your assignment then, should you chose to accept it, is to find a suitable 30-40mm smoothbore barrel in the meantime.

Dewey, what's the best strategy - antenna in a synthetic body, or metal body hooked up to the antenna?
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Unread postAuthor: dewey-1 » Sun Apr 22, 2012 3:57 pm

jackssmirkingrevenge wrote:Isn't a hard epoxy a better idea to make it resilient to shock?


If you want it to be permanently contained forever!

The Silicone based coatings will also help with G-forces but can be removed if needed.

I guess there are two ways to look at the shock involved whether it is brittle (hard coating) or a rubbery (softer coating).

We can analyze this once we see the size and difficulty with the board layout. Potential problems like batteries, switches and whatever during the encapsulation or coating process.
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 22, 2012 4:06 pm

dewey-1 wrote:If you want it to be permanently contained forever!


No problem with that :)

We can analyze this once we see the size and difficulty with the board layout. Potential problems like batteries, switches and whatever during the encapsulation or coating process.


Indeed, just speculation until I receive the stuff.
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Unread postAuthor: MrCrowley » Sun Apr 22, 2012 4:06 pm

jackssmirkingrevenge wrote:Cool :) your assignment then, should you chose to accept it, is to find a suitable 30-40mm smoothbore barrel in the meantime.
Had a quick check on an auction site, nothing in my price range yet. Found some perfect tube (42mm O.D. x 2.7mm) but they wanted $40NZD a meter.

There's also this but I assume it has a seam as it's scaffolding tube. The I.D. comes in at a touch over 41mm as well.
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 22, 2012 4:20 pm

No rush, you have at least a month before I receive the stuff and then put something together.

As to tracking, I wonder if there are part-DIY options that would also be effective.

There are plenty of cheap spy gadget detectors: http://www.ebay.com/itm/Wireless-RF-Sig ... 19d008dccd

I wonder if it would be cheaper to buy one of these and make your own tags.

This mini-tracker probably already linked to in this thread uses an FM radio as a detector, going to see if I can get a kit.

edit: ordered one of these as well :)

Image

The supplier informed me that the coil should not be potted, in that case some alternative form of support is required because it would definitely be crushed by sudden acceleration or deceleration.
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Unread postAuthor: dewey-1 » Tue Apr 24, 2012 3:42 pm

The FM mini tracker will not have much range.
This type of design has been around for almost "ever"! I know it is close to 50 years. :)
Look closely at the coil. Notice how the air gap is slighly different!
That is how the frequency is fine tuned.

The Guardian Angel 807G you ordered will be much better and less fragile.
It is also a more current technology.
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Unread postAuthor: jackssmirkingrevenge » Tue Apr 24, 2012 11:57 pm

dewey-1 wrote:The FM mini tracker will not have much range.
This type of design has been around for almost "ever"! I know it is close to 50 years. :)
Look closely at the coil. Notice how the air gap is slighly different!
That is how the frequency is fine tuned.


I figured as much, I'm looking on it as "backup"

The Guardian Angel 807G you ordered will be much better and less fragile.
It is also a more current technology.


I'm really curious to see what it looks like inside the tags, it should arrive before the end of the week hopefully :)
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Unread postAuthor: MrCrowley » Tue Apr 24, 2012 11:59 pm

Was just browsing the internet for some small GPS devices. Seems like the small, reasonably priced ones are all data loggers and not real-time trackers. Wish I knew someone in the Department of Conservation so I could "borrow" an animal tracker.
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Unread postAuthor: jackssmirkingrevenge » Wed Apr 25, 2012 12:52 am

MrCrowley wrote:Was just browsing the internet for some small GPS devices. Seems like the small, reasonably priced ones are all data loggers and not real-time trackers. Wish I knew someone in the Department of Conservation so I could "borrow" an animal tracker.


The cheapest one on eBay, the "TK102" type, will send you its location by sms or if you call it, take a look at the "manuel" :D

It has an alarm button, you could configure it in such a way that an impact activated switch would transmit its position as soon as it lands.

The price is quite fair, what I don't like is the size. It uses a cellphone type flat battery but this can be substituted with something more streamlined, the issue is the circuit board:

Image

I guess it could be used as one of the fins :D

Dewey, how would you feel about pouring epoxy on a board like that? aside from the simcard holder of course.

From where I'm standing though, the RF tracker seems like a better idea. It's cheaper than GPS unit and simcard, and you get two tags so can track two projectiles. I also imagine that the tag electronics are much more compact and simple.
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Last edited by jackssmirkingrevenge on Wed Apr 25, 2012 1:01 am, edited 1 time in total.
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Unread postAuthor: MrCrowley » Wed Apr 25, 2012 1:00 am

jackssmirkingrevenge wrote:I guess it could be used as one of the fins :D
The MiniBoy V2? :wink:

A small data logger GPS I found even gave specs like:
Max velocity: 550m/s
Max acceleration: 4Gs

So I wonder if an epoxy coating will even be enough to protect it.
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