sensor help

Discussion in 'General Electronics Chat' started by toolman911965, Nov 26, 2012.

  1. toolman911965

    Thread Starter New Member

    Apr 8, 2010
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    Hello folks, I am in need of some direction and am searching google and everywhere else, but thought you folks could possibly help. I am trying to find a sensor that will detect when someone walks into or out of a room and will sound a prerecorded message. there are commercial units that use motion sensors when you walk by. What I need is either 1: an optical sensor that would activate when the light is broken, so that it could be mounted in a hallway and would go off when anyone walks through the beam. or 2: a wearable alarm that would sound when someone walks into the room with the alarm on them. If anyone has any idea of suppliers of similar devices please let me know . I am also looking on thomas net but am getting all sorts of other sensors as well and am trying to weed it out. thanks in advance,

    Shawn
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Look for the pyroelectric detector for heat sensing (human motion detectors for security lamps often use these. Unfortunately, they will trigger each time there is a start and stop.

    The other option is an infrared LED (light source) and photo transistor.
    There are many circuits around the net for these beam break type sensors. The LED and photo transistor are available as a pair from radio shack stores for about 3 dollars. Otherwise, you can get the pyroelectric sensor ($1 and photo transistors ($0.20) and IR LEDs (~$0.10) at www.taydaelectronics.com plus a few dollars shipping (and a week or two of waiting).

    I would personally go with the photo transistor solution - especially if everyone is moving forward. You can even space two sets about 6" apart to make sure people are not just moving into the beam and back out - a smart circuit will only trigger when both are fired in the right sequence. The only problem will be if people are too close together and a gap in the beam does not occur.

    By the way, this is the same circuit that makes sure nothing is blocking a garage door on automatic garage door openers and may other household devices.
     
  3. toolman911965

    Thread Starter New Member

    Apr 8, 2010
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    Thank you. My electronics is quite rusty and I am basically looking for off the shelf if at all possible. I know they have motion sensing alarms that allow for prerecorded messages, I am hoping to find similar with photoelectric type sensor if possible. I will look at your links and see if any help comes from it.
     
  4. elec_mech

    Senior Member

    Nov 12, 2008
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    I'm not familar with an all-in-one solution, but you can use IR beam detectors with a pre-recorded message module.

    Option 1:

    http://www.smarthome.com/77587BK/SE...Curtain-IR-Motion-Sensor-2-Beams-Black/p.aspx

    used with

    http://www.radioshack.com/product/index.jsp?productId=2102855

    Note the sensor requires 12VDC and the sound module requires 9VDC. Normally open relay contact is connected to the switch on the sound module to simulate a button press when the beam is broken.

    Option 2:

    http://www.electronickits.com/kit/complete/elec/ck1620.htm

    with

    http://www.radioshack.com/product/index.jsp?productId=2102855

    Connected same as above. This would require you to solder the kit together, but both units require 9VDC, so you could use the same supply without any modification. Also a less expensive option.

    Another idea is to use a USB recordable module that allows you to load one or more mp3 or wav files to play. It can be set up to play a different sound/song/message everytime the sensor is tripped. http://store.bigdawgspromo.com/prod...12955&osCsid=cc2f08cd97937ffcfbe669fda0da1977

    Again, the input voltage is different from either beam detector, but they are battery-operated and probably won't require frequent changing.
     
  5. toolman911965

    Thread Starter New Member

    Apr 8, 2010
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    Actually, there are some good sources on there and thinking about what I need, I realize it may be better to have something similar to the devices you attach to your children and if they get a certain distance the alarm sounds, except i need it the other way, when the sensor gets close to the device an alarm sounds for a certain amount of time then resets until it moves away and then alarms again when in a certain range. I think this would be a better option, this way you carry the base on your keychain and then when you approach your door it reminds you to grab say your wallet, or to turn off the lights, or whatever you want it to say. Basically this would be more of a radio frequency system.

    best regards,

    Shawn
     
  6. elec_mech

    Senior Member

    Nov 12, 2008
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    It will be easier for us to help if you can define your requirements. You first mentioned using door beams or wearable alarms, now it seems you've changed how you want to do whatever you have in mind.

    So want a system to do the following?
    1. User carries/wears sensor.
    2. When sensor is in range of detector, detector sounds a noise/warning/etc. one time, regardless of time sensor remains in detector's range.
    3. Detector is reset when sensor leaves detector's range.
    Is this correct?
     
  7. toolman911965

    Thread Starter New Member

    Apr 8, 2010
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    I apologize, I was originally thinking of a door sensor, but then realized it would go off constantly if there are a lot of people in the room. What I need is for one or more people to wear a device which sounds an alarm say within a certain number of feet of a device, perhaps for example five feet of a table where the wallet is kept, or perhaps four feet from the fridge perhaps if a person is on a diet and when they go near the fridge an alarm sounds reminding them of their diet. the person would then proceed and the alarm wont sound again until they move away and then back near the item again. Not sure if that makes it easier. The original idea is still viable, but after I looked at what I need closer this is more practical. This way, say for example the whole family is trying to lose weight, they all could wear an alarm with the same frequency so when each gets near the fridge it would go off, or whatever other device you wish to use this for. I am not sure if the units that are used for children would be easily converted to alarm when they get close to each other rather than apart. any help here would be appreciated. it is not of great importance just something I thought would be a neat project.
     
  8. toolman911965

    Thread Starter New Member

    Apr 8, 2010
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    Sorry, my reply went after I corrected it elec-mech, Yes you are correct. On when comes near detector, sounds once, resets after moving away.
     
  9. elec_mech

    Senior Member

    Nov 12, 2008
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    Hmm, this would be challanging, at least to me.

    You're wanting something that contantly transmits a wireless signal so when it is within range of the receiver, the receiver goes off once. The problem here is you'll need to replace batteries on the transmitter almost constantly if left on all the time or find a receiver (which will presumably be plugged in) that constantly emits a signal and looks for the transmitter much like how toll booth devices work for the quick/EZ/etc. pass. Not sure you want to constantly be sending an RF signal or replacing batteries all the time.

    As a proof of concept, you could probably hack one of the wireless child alarms you mentioned earlier. In effect, you connect a switch or relay to siren and have it work in opposite to the siren, e.g., trip when the transmitter is close and remain open (off) when the transmitter is out of range.

    Another thought is make an application for a smart phone that accesses the GPS and have the phone play a message when someone is in the desired vicinity. Probably won't be extremely accurate or quite the close range you want, but it's a thought.
     
  10. gerty

    AAC Fanatic!

    Aug 30, 2007
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  11. toolman911965

    Thread Starter New Member

    Apr 8, 2010
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    Basically that is it elec mech, I need something the reverse of the child monitor. This is basically for something such that , though I cannot give explicit details due to patent and or other issues, say you have ten rooms in the house, all occupants would wear one part of the sensor, and then when you, say go into the kitchen a voice alarm on the wall in the kitchen would say 'wash your hands', or if you are in the bathroom the same thing, or if you go in the hall to leave a message would say to turn off the lights or turn down the heat. The wall mount alarms are great, and they have motion sensing alarms that are recordable, but the problem is that they would go off constantly, especially if you had a bunch of people moving around. These would basically need to turn on once, then reset after you are a certain distance away. so that if you move around the room it wont go off again until you leave the room. I am not sure how to reverse the child alarm sensors though.
     
  12. toolman911965

    Thread Starter New Member

    Apr 8, 2010
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    Actually folks, I came up with the concept of what I need, just have to find the circuitry. RFID systems such as used in stores and the person would wear the tag and when they go near the transmitter it would go off. Either it would have to reset or perhaps push a button to reset it. not sure yet how to go about this but I am sure i will find something.
     
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