Sentry Gun Project

[jackssmirkingrevenge]

Well, the first bit of hardware is finally here

For work to begin on the turret though the postman still needs to get me the following:

Serial-USB adapter <--- edit: arrived

Elevation and traverse servos

Battery box & associated wiring <--- edit: arrived

Webcam

As to the gun itself:

Trigger servo

1/8" ball valve

Webcam

1mm BBs

I'm not sure if my local hobby store stocks 1mm I/D tubing for the barrel, if not I have some nice 1mm diameter piano wire that will make for a good casting. Looking at that wire made me realise how small the calibre is and how pathetic power will probably be at more than a couple of metres distance. This isn't a problem though, the program is really only good for a fixed range as it sees in 2D and therefore cannot make appropriate adjustments for windage and projectile drop anyway.

[bradisfun]

looking good if this works out i might have to try and find a way to make it cheaper and give it ago

[jackssmirkingrevenge]

I don't think you can really make it any cheaper, there's a lot of components involved and even at the lowest prices they still add up if you're on a student budget.

[bradisfun]

yeah i would be on a student buget , i'll have to see when u finish

[rp181]

I think it could. On that board, it seems all there is is a RS232 interpreter (can be had for $2 or sampled) and a mux.

[bradisfun]

hmm i did just read the whole thread, again and i cant see anything about what computer - laptop u are going to be useing. i think that i will deffs be trying this and will probs use a "eee pc" as there not to expensive and i think will beable to run this, the olny problem i have come up with is an air source i think that i'll just go with a co2 bottle filled with air from a frigey then reged down to nlike 200 psi i duno, this would be awile away

[jimmy101]

Just about any old PC should be able to handle the sentry gun. Heck, a 15 year old win98 PC should be able to do it. Add a $20 web cam, couple $4 stepper motors, $10 worth of electronics parts for the drivers, a $5 power supply from an old AT class PC, some Legos or an old Erector Set for the framework ...

Use Win98's internet server software (ISS) and set the camera up as a web cam served locally that auto refreshes. C, C++, Perl etc. to capture the web image and do the number crunching. Control the steppers via the printer port.

Sounds like fun.

[iknowmy3tables]

I'd love to lend you my computer for deployment into harsh terain and resistance to returned fire, but I need it for school

[bradisfun]

yea im use my school computer tho as i have (and am useing now) an alienware gameing laptop so i could use that for school

[jackssmirkingrevenge]

I'd love to lend you my computer for deployment into harsh terain and resistance to returned fire, but I need it for school

Nice, though I don't really want mine to be portable (for which read "I'm not going to buy a laptop just for the sake of having a portable sentry gun").

No progress on the turret parts list, though I have received the 1/8" ball valve I intend to use on the BBMG, it doesn't need much effort to open so the trigger servo should cope with it nicely

[iknowmy3tables]

[quote=jacksmirkingrevenge]1mm BBs

I'm not sure if my local hobby store stocks 1mm I/D tubing for the barrel, if not I have some nice 1mm diameter piano wire that will make for a good casting.[/quote]

wait did you say you were going to use 1mm bbs I didn't exactly read the whole thread but I couldn't find the keyword "1mm" in any of the pages, where do you get 1mm bbs, that sounds like a sand blaster only but at 800psi, I suppose you need 800psi to propel projectiles out a 1mm barrel What made you choose this projectile? have you used it before?

[POLAND_SPUD]

he mentioned it here

It makes sense if you think about it... I really wouldn't like to have something that could cause injuries on a turret that is autonomous

[jackssmirkingrevenge]

that sounds like a sand blaster only but at 800psi, I suppose you need 800psi to propel projectiles out a 1mm barrel What made you choose this projectile? have you used it before?

POLAND_SPUD's link outlines my reasoning, looking at my 1/8" ball valve it actually has 5mm porting so would not have to turn much to allow 1mm BBs through, I think I'll have the ball valve between the chamber and the barrel for maximum efficiency. At 800 psi energy will be tiny but near-supersonic velocities combined with high rate of fire should make for some decent damage at close range.

I really wouldn't like to have something that could cause injuries on a turret that is autonomous

I'm pretty sure the potential for injury will be there (where would the fun be otherwise ) but definitely not as bad as 0.177" BBs, plus as I mentioned it can "safely" be fired in all directions as velocity will drop significantly with range, the same logic behind birdshot from a shotgun.

[jackssmirkingrevenge]

Update on the parts list, still waiting for those all important servos but otherwise most of the bits have arrived. Those 1mm BBs are *really* tiny, I'm curious to see how they will perform. I also found a better deal, 100 grams (that's over 20,000 BBs) for $10 posted.

Edit: turns out I did have some 1mm tubing after all, did some single shot testing with 2 feet of this made as a barrel insert for the V2 pengun at 800 psi. The little things will happily punch through both sides of a beer can a few inches away but only dent a second can, and will not penetrate the bottom of a can.

Not bad when you consider it has the same sort of muzzle energy as a 0.25 gram airsoft BB at 150 feet per second, and these are just single shots, with a BBMG firing 50 shots per second it will be a different story...

[POLAND_SPUD]

that's over 20,000

yeah and over 9,000 too

so far it looks good