unseen wombat
Newbie level 4
this is what I want to do. it’s been a long time since I worked with electronics, so I’m kinda clueless. I have several questions and I’ll ask them as I explain my purpose.
I’m sick of people sneaking up behind me at my cubicle at work (dammit! It just happened again while I was typing this)! and catching me surfing the internet, posting to forums, etc. and I need some kind of advance warning when they’re coming. I’ve thought of tons of different things (I’ve added them at the end of this post if you care to look), but the two which keep popping up as the most practicable are the following:
1. rig up a pen laser under my cubicle wall to shoot along the floor, reflect off a mirror placed strategically across the hall (under a cabinet as to be inconspicuous) and shoot back under my cubicle wall to a phototransistor which, when someone steps on the beam, will trip a circuit to an led sitting on my desk.
2. do practically the same thing, but with a matched infrared emitter and phototransistor detector. the emitter will be set up across the hall (underneath the cabinet), and the receiver will be set up under my cubicle wall. it will then trip the circuit to the led when someone obstructs the ir beam.
my questions are as follows:
for option 1:
a. I’d like to rig the laser up so that it doesn’t have to use batteries, because it’ll be running for several hours at a time. and while I absolutely love throwing money away, I’d rather not be troubled with changing batteries every other day. I have a power strip beneath my desk, could I get an ac to dc converter that I could attach to the contacts of the laser pen and run it that way? will I need some fancy honking resistors and diodes and stuff?
b. the trouble with the laser pen is if someone sees a big red dot on their foot, they’re gonna wonder what the hell is going on, trace the beam back to its source under my desk and then I’m f***ed. so what I need is to rig the circuit up such that when the laser beam is tripped the laser shuts off, while at the same time turning on the led so I know someone is approaching. it would be good if the led only flashes momentarily, so anyone coming to visit me doesn’t see a bright green or red light sitting on my desk. how would one do that? I think the item I would need is called a “flip flop”? but I don’t know how to use it. and some transistors or something? I’m clueless, I know.
for option 2:
a. the cabinet is about 15 feet away from my cubicle, and that’s about the closest inconspicuous place I can set this up. I’m thinking of using these: https://www.radioshack.com/product...._name=CTLG_011_002_017_000&product_id=276-142 is it even possible for that particular transmitter to send a signal 15 feet? I would think so. but can anyone verify that for me?
b. provided that the transmitter can reach 15 feet, if someone steps in between it and the phototransistor, will the connection be sufficiently broken to trip the circuit? I know with my infrared tv remote at home, someone can be standing between me and the tv and it’ll still work. if that’s the case, it looks like option 2 will be out.
thanks anyone who can help me.
addendum: stuff I’ve already thought of, but won’t work. skip this if you don't care.
1: get a pir motion detector:
the problem with this is I don’t trust these things. we have one set up on our garage to turn the lights on when someone walks by. sometimes it works immediately, other times, I can jump up and down, wave my arms frantically, run back and forth and still the damn thing doesn’t work. not good for such a sensitive application as this.
also, I certainly don’t want anything as obvious as a chime going off when someone walks by, and most of the motion detectors I find have a 95 dB chime or a barking dog noise or some such obnoxious thing. I suppose I could take it apart, remove the noisemaker and rig up an led. but that’s probably beyond my skills.
finally, every one I’ve seen is way too big to use inconspicuously given the layout of my cubicle.
2: use a webcam and some motion detection software (i.e. “digi-watcher”).
the problem with this idea, which is great otherwise, is that my cheap-ass boss has windows nt 4.0 running on these OLD ass computers. we were supposed to get upgrades to xp like 2 years ago, but that didn’t pan out. I asked him about it about a month ago and he said, “we have some cash-flow issues we have to sort out first.”
yeah. right. sure we do.
and as you may or may not know, windows nt 4.0 doesn’t include usb support and just about every webcam in the universe is now usb only and there are no adapters to convert usb to serial. only the other frigg’n way around. I’ve seen serial port webcams on ebay, but I don’t think they work with the software.
I know there’s a usb driver by dell for nt 4.0, but I tried it and it didn’t work with a webcam. (one of the few things, of course, that it doesn’t work with).
3: just do my job and be a good little boy, always industriously working on work-related items:
hahahahaha :lol:
I’m sick of people sneaking up behind me at my cubicle at work (dammit! It just happened again while I was typing this)! and catching me surfing the internet, posting to forums, etc. and I need some kind of advance warning when they’re coming. I’ve thought of tons of different things (I’ve added them at the end of this post if you care to look), but the two which keep popping up as the most practicable are the following:
1. rig up a pen laser under my cubicle wall to shoot along the floor, reflect off a mirror placed strategically across the hall (under a cabinet as to be inconspicuous) and shoot back under my cubicle wall to a phototransistor which, when someone steps on the beam, will trip a circuit to an led sitting on my desk.
2. do practically the same thing, but with a matched infrared emitter and phototransistor detector. the emitter will be set up across the hall (underneath the cabinet), and the receiver will be set up under my cubicle wall. it will then trip the circuit to the led when someone obstructs the ir beam.
my questions are as follows:
for option 1:
a. I’d like to rig the laser up so that it doesn’t have to use batteries, because it’ll be running for several hours at a time. and while I absolutely love throwing money away, I’d rather not be troubled with changing batteries every other day. I have a power strip beneath my desk, could I get an ac to dc converter that I could attach to the contacts of the laser pen and run it that way? will I need some fancy honking resistors and diodes and stuff?
b. the trouble with the laser pen is if someone sees a big red dot on their foot, they’re gonna wonder what the hell is going on, trace the beam back to its source under my desk and then I’m f***ed. so what I need is to rig the circuit up such that when the laser beam is tripped the laser shuts off, while at the same time turning on the led so I know someone is approaching. it would be good if the led only flashes momentarily, so anyone coming to visit me doesn’t see a bright green or red light sitting on my desk. how would one do that? I think the item I would need is called a “flip flop”? but I don’t know how to use it. and some transistors or something? I’m clueless, I know.
for option 2:
a. the cabinet is about 15 feet away from my cubicle, and that’s about the closest inconspicuous place I can set this up. I’m thinking of using these: https://www.radioshack.com/product...._name=CTLG_011_002_017_000&product_id=276-142 is it even possible for that particular transmitter to send a signal 15 feet? I would think so. but can anyone verify that for me?
b. provided that the transmitter can reach 15 feet, if someone steps in between it and the phototransistor, will the connection be sufficiently broken to trip the circuit? I know with my infrared tv remote at home, someone can be standing between me and the tv and it’ll still work. if that’s the case, it looks like option 2 will be out.
thanks anyone who can help me.
addendum: stuff I’ve already thought of, but won’t work. skip this if you don't care.
1: get a pir motion detector:
the problem with this is I don’t trust these things. we have one set up on our garage to turn the lights on when someone walks by. sometimes it works immediately, other times, I can jump up and down, wave my arms frantically, run back and forth and still the damn thing doesn’t work. not good for such a sensitive application as this.
also, I certainly don’t want anything as obvious as a chime going off when someone walks by, and most of the motion detectors I find have a 95 dB chime or a barking dog noise or some such obnoxious thing. I suppose I could take it apart, remove the noisemaker and rig up an led. but that’s probably beyond my skills.
finally, every one I’ve seen is way too big to use inconspicuously given the layout of my cubicle.
2: use a webcam and some motion detection software (i.e. “digi-watcher”).
the problem with this idea, which is great otherwise, is that my cheap-ass boss has windows nt 4.0 running on these OLD ass computers. we were supposed to get upgrades to xp like 2 years ago, but that didn’t pan out. I asked him about it about a month ago and he said, “we have some cash-flow issues we have to sort out first.”
yeah. right. sure we do.
and as you may or may not know, windows nt 4.0 doesn’t include usb support and just about every webcam in the universe is now usb only and there are no adapters to convert usb to serial. only the other frigg’n way around. I’ve seen serial port webcams on ebay, but I don’t think they work with the software.
I know there’s a usb driver by dell for nt 4.0, but I tried it and it didn’t work with a webcam. (one of the few things, of course, that it doesn’t work with).
3: just do my job and be a good little boy, always industriously working on work-related items:
hahahahaha :lol:
I ca n look around at some surplus stores maybe. that’s an excellent idea though, thanks for the suggestion.
