Well, it all started when I accidentally bypassed the voltage regulator on my
Arduino (thus reducing an amazing bit of technology to a USB powered fire hazard).   I needed something to fill time while a new one shipped to me.  Then it hit me--the Nerf dart, I mean--and I realized what I wanted to build.  So, without further ado, I will show you how to build a laser tripwire sentry nerf bomb with a few parts form Radio-Shack and Jameco, and a pet-toy laser pointer. It's also worth pointing out that the tape on the canister you see in the picture has no apparent use. It did in a previus prototype, but you need not add it.. To briefly describe the end result, we will be building an elastic-loaded canister which can fire 4-5 Nerf darts at a person when that person walks through the laser beam. i call it the sentry bomb and it's great for Nerf games and startling you're freinds. Not to mention that with minor modifications you could turn it into a security device, minor modifications like replacing the launcher with an alarm. If you're new to electronics, then the circuit might be tricky for you, but once you understand it, its really quite simple. Have fun building!

To the parts list!

Step 1: parts list

The primary problem with building things is that you need the correct parts to do so. Ah well, the best I can do is tell you were to buy them I guess.

LM393AN voltage comparotor or similar ----------- Jameco part # 212177 1.90$ for 10
cadmuim sulfide photoresistor ----------Jameco part 202411 1$ each
approximately 2.3 K ohm pot
0.3 K ohm resistor and 0.68 K ohm resistor  (actuly I used two to make the 0.68 K ohm one)
one LED
a solonoid ---------- Jameco part # 1919191 10$ each
a 2-pole 2-thingy switch. aka one with two separate switches in one and three posts per switch
a cat laser. I got mine at wallgreens for 5$
a soldering board----------Radio Shack, but I don't remember the price
pnp amplification transistor. It doesn't really matter which one I think. i just found one lying around.
solderless breadbord for prototyping----------Radio Shack, butI I don't remember the price
hot glue, solder, elastic, a rubber band, batteries, Nerf darts or similar, 2 small nails, two peices of K'nex or a dowel or somthing, cardboard and wire.

I think that's it.  Boy, it didn't seem like that many things when I was rooting though my box-o-junk for parts. Also this parts list is for one sentry bomb, and as we all know, the more the merrier! In case you don't know about Jameco, it's a really good online electronic supply store which can be found here.
nice. the video was great.<br>
Almost 80 people have read this sombody tweeted about it and sombody else has a link to it on facebookk and yet nobody has commented or rated it. If anybody likes this instructable, now is you're exclusive one time only chance to influence my next project, which will be posted on instructables. I would like to build an electronic device that is either ussfull or a nerf compatible wepon of some sort and any suggestions would be apreiciated. Also if anyone builds this tell me so I can brag to my freinds &gt;=)
Give it a little while. It's been up for three days. No need to go promoting yourself everywhere just yet. Although that is pretty cool.
No kidding, he was complaining about how this wasn't featured on a different instructable.
Yeah I saw that
yeah thats how i found this thing actually
Ditto, and it isn't very good either.I already have 5 methods that would work better, excluding a couple i had a while ago.
I dident put the twitter about it up, sombody else did, no idea who. As for the facebook reference, that was actuly my mom so that dosent say much for the size of my audiance. anyway you guys may have missed you're exclusive chance to influance my next project becaus im brainstorming on cat toy/ dog toy/ alarmclock that would wait a while and than go ziping around very fast untill somone cought it. it would have an onboard treat for dogs and an onboard buzzer for an alarm, as for cats they don't need any more motivation than movment to go berserk and attack somthing. my cat hides under the couch and amushes peoples feet. im thinking that wouldent be to hard...speed would be an issue but i've done obsticle detection. now i just need another arduino and a few gearheads. I can't wait!
the main perpose of saying that was so you would find this. I wasn't actually upset and I hope I didn't seem so. I do find it funny that a fart joke got featured but I didn't expect this instructable to be featured either so that's just fine =). I am quite glad I did so, as it seems to have attracted a lot of visitors, and I'm guessing anyone who found me though a tech instructable is interested in tech instructables so the people who I get that way might actuly build this. also can anyone explain the order of comments? they arent showing up in chronological order... it is most confusing. anyway i need to get back to work on my next project so goodnight! isent it cool how the things we build for ourselves can be veiwd by people all over the world? I've gotten a lot of ideas from othe instructables to. even better than wikipeidia
This is a very good build. Great idea, well executed. At a guess, I'd say your barrier to being featured would be either that it hasn't been seen by an editor yet, or they are concerned about your text. I just gave this a cursory glance, and I spotted a number of typos, run-on sentences, and other errors that make your steps tricky to read. I know Instructables isn't English class, but it pays to take the time to go back through and check for errors, add some paragraph breaks, and generally make it more readable. Your best bet, by the way, is to do this with a friend. You'd be amazed at what a second set of eyes picks up. Oh, and in my experience (not vast, to be sure) I don't generally see my first rating until I've passed 200 views, and usually I'll get a few ratings before my first comment. Unless I got something wrong. Then the comments hit fast! :-)
thanks! its nice to have some real feedback for once. as for the writing though, i am actuly terrible at grammer spelling and the like, although im fairly good at delivering content. my mom on the other hand is a profesional writer, and she is the one who looked over this and corrected all the mistakes. next time though i will write the whole thing in microsoft office word before i put it on instructables. I'll certainly look over it again though, as i said i would hate for someone to go un-shot becaus of bad writing on my part! =) as for hit count i was expecting an initial surge while it was on the recent list and than a rapid slowdown after as few days. you are obviusly right though, thats not how it works at all.
LOl you guess don't actuly read the whole comment when i leave a long one do you? well I am new to building things of this sort, my speciality is actuly java, I just got tired of having my creations stuck on the screen. If you have methodes which would work better I would very much like to hear them since its hard to learn everything from books. since you know about this stuff btw how could i make a semi-outomatic gun for an arduino project? i was thinking i would have a pnumatic resevuar which would lead to a long tube with the projectile in it through a solonoid operated valve. help is alway apreciated! =)

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Bio: Howdy! How ya doin'? I'm Michael, and I LOVE to build. My workshop is a mess, my room has scattered devices across the floor ... More »
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