Instructables
Picture of Intruder Sentinel
Tired of always being snuck up upon? Doing any stealth surveillance or reconnaissance? Or maybe you just need to set-up a fail-safe alarm for your stuff so your little brother doesn't go into your room.

Well this little ingenuity will allow you to not only trip someone but also have it set off an alarm when tripped. Its a fairly easy circuit to build and is incredibly straightforward. You shouldn't have any problems with this circuit at all, but if you do we're here to help.

For more similar projects, kits for this and other gadgets, and much more just go to Ocalon Electronics. If your having any problems with getting the circuit to work, or just general Q&A questions feel free to leave them here.
 
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Step 1: Parts List

Picture of Parts List
Parts List
1. A single .01uF Capacitor
2. A 10K Resistor
3. LM555 Timer IC Chip
4. A SPDT Touch Switch
5. 9V Battery and Clip
6. Piezo Buzzer
7. Perf Board
8. About 8" of wire

Preferably: (Optional)
9. 2 Position Terminal Block
10. An On/Off Switch
11. And a Project Case
rahulhari4 years ago
 will ne555 timer do
LM555 and NE555 are nearly the same.
hackman884 years ago
Its Better to use Laser Than Switch use LDR Or InFrared For Receiver of the Laser
Colonel884 years ago
i tried making it and this doesnt work. I made a better circuit, a double oscillating blinkie light so when one is on the other is off, like those yellow traffic things.
"blinkie light" lol that's awesome
jernax5 years ago
this is a sensor...why need to use SPDT switch?...are you saying that we have to trigger the switch so that it can detect?...maybe its nice to use laser or photo transistor rather than a switch.
jernax5 years ago
this is a sensor...why need to use SPDT switch?...are you saying that we have to trigger the switch so that it can detect?...maybe its nice to use laser or photo transistor rather than a switch.
that is well ot complacated for mi.
lemonie5 years ago
Did you actually build this?
The screen-shot step 3 is particularly lazy (PocketSized's comment noted also.

L
weezoh (author)  lemonie5 years ago
Yeah, that's just a screenshot of the steps. I haven't gotten around to posting the step-by-step instructions yet. I'll try and get on that.
lemonie weezoh5 years ago
It would be good to see them - something you've yet to build? or is it just putting the instructions together? L
PocketSized5 years ago
The schematics for this project are scanned straight from the pages of
101 Spy Gadgets for the Evil Genius (With slight modification). Yet you didn't feel it worth giving the guy credit?
No link, not even a brief mention?

While part of the Instructables community thrives on the well documented reproduction of projects. It does not appreciate other peoples ideas/projects being stolen soo blatantly without even a mention of the original creator...

This is without taking into account the copyright implications of scanning in the original owners schematic.
While it could be argued that the circuit is soo simple anyone could have coincidentally come up with it, this doesn't account for the identical schematic.
Which shows there is no coincidence, coupled with the fact you didn't even feel the author of the circuit deserved a quick mention.

I have added a photo of the original circuit graphic, just as proof.
However because I value the original authors' work I will remove it shortly.
Schematic.jpg
weezoh (author)  PocketSized5 years ago
You're absolutely correct! I did have an image caption about how this project is a variation of the one built by Brad Graham. I'm not sure what happened to it. But I have updated the image so the caption is included in it. Thanks for the reminder =)
KillerPanda5 years ago
Could I build it? I know the bare minimum about electronics, but I could probably follow the instructions depending on if it is suitable for novices.
weezoh (author)  KillerPanda5 years ago
Yeah, this is a pretty basic circuit so you shouldn't have any problems, but if you do just let us know or post it to our forum and we can help you out.
looks simple enough for a novice, if u can solder. just dont allow the components to get too hot while soldering ;) (allow time to cool between soldering pins and legs ;) ) if soldering tutorials are needed there are plenty here on instructabubbles.
Chips, like a 555, contain semiconductors very sensitive to static electricity and to heat. It might be safer to spend a very little extra and get a socket for the 555. After it is soldered, insert the chip. A socket could make life easier, especially for a novice.
weezoh (author)  Phil B5 years ago
Sockets are definitely a great idea because you can take the chip in and out whenever you need to. That way you can switch out a broken chip for a new one or use that same chip later on if you decide to scrap the circuit.
yea what he said :) its best not to chance it with chips.
KillerPanda5 years ago
Also, how much do the parts cost in all?
weezoh (author)  KillerPanda5 years ago
The most expensive parts of the circuit include the buzzer and the project box, other than that everything can be purchased relatively cheap like zaketus said. We just put up project kits and a starter kit in case you need the parts for this specific projects or just need some general equipment and materials for general hobby projects. That should help take the hassle out of trying to find the right parts especially finding a buzzer that works with the circuit. Plus the kit is cheaper than just buying all the parts individually at Radio Shack.
I'm not sure about difference on price of electronics between European and American stores, but those won't cost much. I'd say you could get those components for 2$ and lets say 2$ for perfboard (+shipping, if ordered...) , that is big enough for other circuits.