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Capacative touch sensor for a VERY large object? - Page 2 — Parallax Forums

Capacative touch sensor for a VERY large object?

2

Comments

  • SRLMSRLM Posts: 5,045
    edited 2008-08-13 05:27
    For the laser, I'd use a comercial model (stanley makes one) that measures distance. You'll have to figure out how the signals that it sends to start measurement and send the results, but I think it would be much easier than building your own circuit since you have to worry about duplication and wire lengths and all that.

    If you haven't already, consult this forum:

    http://forums.parallax.com/forums/default.aspx?f=25&p=1&m=276820

    And a Q and A website:

    http://www.repairfaq.org/sam/laserlia.htm


    My suggestion for building the laser: buy the commercial model, take away everything execpt what you need to provide you with TOF or actual distance, mount it in an enclosure with a spining mirror that gives you position feedback.

    This part may be best done by the propeller since you'll want to know the position of the mirror at the instant you fire the laser. You might be able to get by with the stamp by assuming that after you get the position and when you fire the laser the mirror has turned an additional 1/2000 of a rotation (or however much).


    One more thing: make sure that everything you have out there is both difficult to detect (hidden for starters) and not easy to get around. The IR assembly mounted on a stake in your front yard sounds like an invitation to jump over. You could always do some decorative woodwork (4x4s maybe) and mount several at different heights. Just think of pretty much any spy movie, and you get the idea...
  • GICU812GICU812 Posts: 289
    edited 2008-08-13 05:45
    Sorry, what I meant by laser is just a perimiter trip beam, just shoot it from corner to corner, and back to a make\break reciever on the other side of the house.

    So what I need is to build an adjustable mirror assembly, the mirror only needs to be maybe 1"x1", fit inside a 2 1/4" ID pipe.

    I'll need 2 of those. Anyone have anything premade?



    Post Edited (GICU812) : 8/13/2008 5:50:38 AM GMT
  • SRLMSRLM Posts: 5,045
    edited 2008-08-13 07:44
    Awww. You take away all the fun. Still, the comment about making sure the intruder can't jump over the beam still stands. Make sure you get a good mirror that a) resists getting dirty and b) doesn't disperse the beam too much. You'll have to look at the specs on your laser, but somewhere it tells you how much the beam diverges. Oh, it's probably best to get an IR laser: More dangerous to the eye and more difficult to troubleshoot, but the intruder doesn't know it's there. Plus, if it's the same wavelength as the IR recievers are designed for then you could use it just like a big IR beam. (Thats a thought: It might be easier to use four lasers on each side of the property than lots of IR LEDs.)

    You could get a mirror that technicians use when diagnosing equipment. They are on the ends of little extendable rods, and some are round. Other sources for small mirrors are craft stores. Keep in mind that these may not be "clean" enough.
  • GICU812GICU812 Posts: 289
    edited 2008-08-13 21:29
    Yea, Ive got a mirror like that, Looks like a good option, I can bolt the base where the extending arm goes right to the pipe. Im just a little worried about it moving over time.

    Any other ideas for mirrors? Ive been searching around, Id really like something where you can adjust screws to move the mirror, would be easier to fine tune.

    I cant find it anymore, but there was a laser mirror assembly with motors that would work for what you are talking about, it was $10, if you're interested.
  • SRLMSRLM Posts: 5,045
    edited 2008-08-13 22:47
    Naw. Thanks, but I have one of my own sitting in the ole' junk box, just waiting to be figured out.

    As for the mirror mounting, it would probably be easiest and cheapest to make such an assembly yourself. You'll want two: one for each dimension. The assembly could be made from a few parts: a large strap hinge used to hang fence gates, a bolt with a locknut, washer and regular nut, and a sprint. Drill a hole near the end of the strap bigger than the bolt by a couple sizes. Drill on the opposite side to fit the bolt. Solder/ weld the regular nut on the small hole side. Put the bolt through the big hole, put the locknut almost all the way up the shaft, then thread into the soldered nut. Now when you turn the screw it changes the angle of the bracket. Put two of them together, and you get an adjustable mirror assembly.
  • VIRANDVIRAND Posts: 656
    edited 2008-08-13 23:10
    A good thing to use as a laser beam break alarm mirror is either a bike reflector or
    road line paint or road sign paint because they have tiny cube prisms in them.
    These things send most of the light that hits them right back where it came from
    so you can hit it with the laser easily, and just put the sensor near the laser.
  • SRLMSRLM Posts: 5,045
    edited 2008-08-14 00:17
    Consider tilting the mirror/reflector to form a triangle shape. You'll have to move the reciever away from the laser vertically, but you'll get more coverage.
  • GICU812GICU812 Posts: 289
    edited 2008-08-15 02:34
    I dont follow you on the triangle, but heres my design based on your previous suggestion.

    13577_.jpg
    [noparse][[/noparse]IMG]http://myfiero.com/uploads/13578_.jpg[noparse][[/noparse]/IMG]
    [noparse][[/noparse]IMG]http://myfiero.com/uploads/13579_.jpg[noparse][[/noparse]/IMG]
    [noparse][[/noparse]IMG]http://myfiero.com/uploads/13580_.jpg[noparse][[/noparse]/IMG]
    [noparse][[/noparse]IMG]http://myfiero.com/uploads/13581_.jpg[noparse][[/noparse]/IMG]
  • GICU812GICU812 Posts: 289
    edited 2008-08-15 02:36
    13578_.jpg
    13579_.jpg
    13580_.jpg
    13581_.jpg
  • GICU812GICU812 Posts: 289
    edited 2008-08-15 02:39
    Its just two hinges welded together (sloppily, even on its lowest setting my MIG was too powerful, but itll hold)

    Then I drilled a hole through the middle of each hinge, welded a nylon locknut on the back (with lots of quick welds and water) and put a machine screw in each.

    Then used tapered head screws and put a nut on the back to make mounting studs.

    Then wrapped womens hair ties (all I had on hand, lol ) for the return spring movement

    Then super glued a mirror to the top hinge.

    I have adjustment on X and Y axis, about -5* to 45*
  • SRLMSRLM Posts: 5,045
    edited 2008-08-15 06:11
    Your adjustment hinges look good. The triangle idea:



    · Laser Beam
    ········ |
    ········ |
    ······· \/
    |· |········ |X| <-- Receiver
    |· |······· /|· |
    |· |······ / |· |
    |· |···· /·· |· |
    |· |·· /···· |· |
    |· | /······ |· |
    |· |/······· |· |
    |O|
    |~|·· <-- Laser
    |· |········ |· |
    |· |········ |· |
    |_|_____|_|___· <--Ground



    What I would give for some graphic software... Anyway, the idea was to get a bit more bang for your buck. It covers more area and would be just as easy to adjust. More mounting required though.·······························
  • GICU812GICU812 Posts: 289
    edited 2008-08-15 16:46
    MsPaint [noparse];)[/noparse]

    Sorry if I didnt convey this before, im using 2 mirrors and bouncing the laser around above the fence. Here is a pic, red dots are laser diodes, blue are IR diodes, and green are recievers.
    13582_.jpg
  • GICU812GICU812 Posts: 289
    edited 2008-08-15 16:47
    Oh, the big green things are trees [noparse]:)[/noparse]

    And no, thats not to scale, haha
  • SRLMSRLM Posts: 5,045
    edited 2008-08-15 22:02
    Ah. Okay. I forgot that you were using the lasers above the fence. A tree in the front yard. Hmmm. Sounds like a good spot to put a camera activated by a broken beam. So are you going to have a deactivation system for when you are about to arrive home? Or will it be on a timed type system: push the code in at the back door, exit, and three minutes later the system is activated? Anyway, you could use the PINK module to monitor the house on long trips and prepare settings for when you get back. (Not just security, either: temperature, lights, door locks [noparse][[/noparse]for friend admission], and so on...)

    What is the black line in the back yard. It looks like a fence. If so, the laser is on a slanted plane?

    about paint: I don't like it since the zoom levels leave something to be desired. Plus it's almost more fun to use text. I'm waiting until I get student discount so I can buy Macromedia software.
  • GICU812GICU812 Posts: 289
    edited 2008-08-16 02:16
    Black line is the fence, to save materials and trouble, I'm not following the fence exactly.

    The perimiter alarm is going to be more of a passive alarm, I think. More like, if it goes off at 3am, so I can go check it, rather than when i'm away or anything, since there are still modes of false alarms. Though I will program out the driveway sensor during time windows when I know we will be coming and going. The house allready has an installed alarm system I'm going to tap into and use that for the actuall alarming, a few door sensors, some PIR sensors etc.

    I was thinking about getting a PINK module, but they are rather expensive, it might be easier to use the BS2 to interface with a PC, and write a program to send SMS alerts.

    I was thinking about integrating the thermostat, wouldnt be hard, just need a couple of relays, and actually, with an IR transmitter, I could tie my remote gas fireplace in as well, I have electric central heat, with a 20kw unit in the furnace, so its a little pricey, the fireplace is a nice supplement, I could use the stamp to balance the two.

    I also have an RFID reader, and I would like to mount it on the front door and get an electronic deadbolt, so I can swipe a RFID card to unlock the door.

    Ive also toyed in the past with getting the stamp to control the ceiling lights (I use CFL, so its a little more tricky than a SSR), and I think it would be awesome to integrate a voice recognition module into the system. If I do that, a voice output module is a must!

    If this actually gets off the ground, I'll have to make a new post, havent seen a whole lot of home automation to this degree on here.
  • SRLMSRLM Posts: 5,045
    edited 2008-08-16 03:13
    If you are going to integrate a BS2 to the home security system that you have already, be sure that it doesn't void a contract or anything. I don't know, but the home sercurity company (Brinks, ADT?) may decide that the system can no longer be covered.
  • GICU812GICU812 Posts: 289
    edited 2008-08-16 04:14
    I guess it used to be an ADT system from the stickers, but its not monitored and I dont know how old it is. Im not worried about voiding anything.

    I could either just remove the ADT controller and wire the sensors to the Stamp, or I could decode the ADT serial signal to its keypad, and monitor the ADT controller from there
  • GICU812GICU812 Posts: 289
    edited 2008-08-16 05:46
    Now I need to come up with a mount for the laser to hold it inside the fence. I was going to use gun sight lasers, because they are adjustable, but I dont think it would fit inside the fence post. Im hoping by mounting the laser inside the fence post, and using a small reticule, I can hide most of the "splash" light that comes off the front. So you would have to be looking almost in line with the laser to see it.

    What I have right now is a laser pointer, I was going to remove the case so I just have the module like this
    200698164242.jpg

    Though you can see where the tip screws on the one in the picture, so its actually shorter, and has a threaded tip.
  • SRLMSRLM Posts: 5,045
    edited 2008-08-16 06:15
    Nice. You have 3/4 of the work all done for you. Probably the best long term solution would be to hijack all the sensors and throw away the rest.
  • GICU812GICU812 Posts: 289
    edited 2008-08-16 06:27
    I do have a BS2P40
  • SRLMSRLM Posts: 5,045
    edited 2008-08-16 06:30
    Probably don't want any potential infiltrator to see the laser: too easy to hide from then... I think I mentioned this before, but I'll go again. If you use and infrared laser then you won't have this problem. Just be sure to hide it anyway since it can damage eyes without knowing. A source of laser modules:

    http://www.roithner-laser.at/All_Datasheets/Pricelists/roithner-pricelist-c-080813.pdf

    Some of them are probably cheaper then a laser pointer. Anyway, if you do have a look then be sure to use something in the 950nm wavelength. Then you could use the IR reciever. What are you planning on using with the red?
  • jazzedjazzed Posts: 11,803
    edited 2008-08-16 07:19
    I had the same question on detecting red laser light earlier today, so I did some experiments. Cadmium-Sulfide photocells responded very nicely with resistance change (they are relatively slow to respond on the order of milli-seconds). The part tested is from Radio Shack and is similar to the one Parallax sells.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
  • SRLMSRLM Posts: 5,045
    edited 2008-08-16 14:45
    The light to frequency chip that parallax sells might work too. Also, you can "focus" your receptor to respond to only red light by using a red lens. This might make it easier for the BS2 to distinguish between the laser and environmental light.
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2008-08-16 22:21
    Hi GICU812

    I have made laser perimeter detectors ... not to put a damper on your laser enthusiam, but an earlier poster mentioned things like animals and weather. As you're still in the R&D phase, here's what you will encounter.

    1. Rain drops keep falling through your beams
    2. Rain sensors on, laser false alarms off - theives are wet or dry...
    3. Dirt on mirrors and laser transmitters, not to mention insects that like to nest in small opennings in fence posts.
    4. Thief speed - faster than a speeding patrol car (which normally responds 1/2 hour after your distress call).

    Your mirror gadget is cool, but you will be better off using * front silvered * mirrors, available from places like Edmund.

    For really cheap lasers, get small laser pointers and just tap wires into the battery holder instead of the battery. Force the on switch on with tape or glue. You can pulse these. I got 20 of them on sale once at ACE hardware for $1 each. Toasted 3 before settling on a design. Parameter is about 100' x 100'. It is used as a ~last!~ resort.

    The psychological counter measures a poster mentioned earlier are actually VERY effective - unless your thieves are crackheads, then all bets on defenses are off!

    Get a new ADT or similar sign. And you might be surprised at what a few good flood lights can do. "Warning Bad Dog!" or "Warning Bad Owner With Shotgun!" [noparse]:)[/noparse]

    cheers
    Howard

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Buzz Whirr Click Repeat
  • GICU812GICU812 Posts: 289
    edited 2008-08-17 03:09
    That rothner place doesnt sell any IR lasers less than $150, or so thats what they told me when they finally responded, half the parts on thier datasheet, and apparently all the IR pointers they have on thier website, are not available. Why they dont remove them ,at least from the website, boggles me. As of right now, I can find no source for IR laser modules.

    I did preliminary testing with CDS cells that showed very positive results.

    If I can work this right, the laser and reciever will be set back inside the fence post with a relatively small apeture, so it should be nearly impossible to see the laser unless you are looking down the line at the laser or reciever. It will be visible when they breach it, if they even notice, it will be too late then.

    As for animals, the laser will be at about 4' level. We dont have a whole lot of animals that size around here. It will be close enough to the fence for an animal going over it to trip allong the back fence, but I'll deal with that as it comes.

    As for dirt, the mirrors, laser, and reciever will be housed inside the fenceposts, which are covered on top, with small enough openings, there shouldnt be any way for water or dirt to get in there more than dust.

    As for rain, I plan on filtering the detector in software, so depending on the actual disturbance time caused by the rain, I might be able to filter it out, or just disable the system during rain.

    As I said, this is primarially for use as an at-home alerter. So when someone trips the sensor by the cars at 3AM, I can go introduce myself. The only thing an auduible, or even police linked alarm does is make the theives a little speedier in their looting. This will be completely silent outside the house.

    I guess if I used the frequency sensor, I wouldnt have to worry so much about shielding the reciever from natrual light, but since Im trying to be covert, it needs to be hidden from sight, which should eliminate most of the ambient light as well. The reciever will proably be mounted at the end of a ~4" black tube about 3/16" in diameter.
  • SRLMSRLM Posts: 5,045
    edited 2008-08-17 04:04
    When you introduce yourself, make sure that you fulfill the "Owner with shotgun" sign. To test for rain, you could just use a sprinkler and see what happens. My guess is that most of the light is refracted. I suppose that if any potential theif were scoping out your house that night, they might see that laser light. However, anyone with that foresight is probably good enough so that your homebrew solutions don't matter. Anyway, you could take a trip to your local police station and ask them a couple of questions, namely: How many break ins occur in rainy weather as compared to dry? My guess is that theifs like to keep the stolen goods dry...

    I think you mentioned somewhere that you live in the NE, so you may want to find out what snow does...
  • GICU812GICU812 Posts: 289
    edited 2008-08-17 04:23
    I figure anyone intent enough to case the house, is doesnt matter what you have, they're going to be able to evade it, professional or homebrew, not to mention they will be well enough organized to be in and out before anyone responds to an alarm anyway.

    I know I can easily bypass magnetic door sensors by holding a neod magnet to the door then openeing the door and sliding the magnet to the sensor. I can bypass the PIR sensors with just a sheet or piece of glass, etc, not talking about my house, but any house in general, and im not even a thief. There are some sensors in my house it is impossible to bypass, but you just have to go around them.

    At anyrate, I've done certain things to slow them down as much as possible. Without going into too much detail, lets just say it would be easier to go through the wall than break in the front or back doors. Then again, you could keybump any of them in less than a minute. The only real people you're going to be able to stop are the petty thieves, kids and vandals, which is what this is designed for.

    Best you can do for professional thieves is deter them, or slow them down and make thier stay uncomfortable.
  • SRLMSRLM Posts: 5,045
    edited 2008-08-17 08:07
    You could bathe your house in extreme infrared light when you are not home. That way, they'll go blind before they know it and will be stuck bumbling around until you get home, at your leisure. Make sure you have a good lawyer friend though...
  • GICU812GICU812 Posts: 289
    edited 2008-08-17 17:49
    Its infrared.... Who would know? Remove the emitter before anyone arrives to investigate.... I dunno... Maybe he had a stroke or something...

    If I could, I would just line the fence with pungee pits, or more realistically, just boards with nails sticking up burried just below he surace.
  • SRLMSRLM Posts: 5,045
    edited 2008-08-17 19:22
    Make sure you get your tetanus shot before you build that fence... Maybe you could build a security guard robot that tosses out caltrops at intruders.
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