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Thread: IR sensors for local presence / distance sensing ...

  1. #11
    Automated Home Legend chris_j_hunter's Avatar
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    well done - that's very encouraging for us, too ...

    BTW - did you have anything particular in mind, Arduino-wise, in terms of extending your HA capability ? 'would be interested to know, because we too have an Arduino starter kit with breadboard etc sitting here in a drawer waiting for us to get back to it when we've done with our final push on our selfbuild (which is currently keeping us just a bit too busy) !
    Last edited by chris_j_hunter; 22nd June 2015 at 10:14 PM.

  2. #12
    Automated Home Legend Paul_B's Avatar
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    Thanks as usual goes to Karam. Not sure if it is possible to get closer to 80cm for detection by changing some of the components?

    As for the Arduino I bought it on a whim after seeing some in action at a local Code Club for Kids that I help out at. I'd like to learn more about electronics and it seemed like a nice package to learn about electronics and play with an inexpensive micro-computer. Although as of now I have not found time to start on this adventure.

    Paul

  3. #13
    Automated Home Legend Karam's Avatar
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    Problem is that the output voltage from the sensor at longer distances is dropping below what is needed (~0.7V) to turn on the transistor. A simple option might be to use a germanium transistor which has a lower base voltage requirement but you'd be hard pressed to find one these days :-). The next two options in my mind are: op amp - to keep it as dc and for good control of characteristics, or second is to treat it as an ac signal (since you are only after a change when someone passes by anyway) and try and create a suitable ac amplifier with the transistor. This would mean coupling the signal between the IR sensor and the 4k7 resistor using a capacitor (say 47uF with + at resistor side) and biasing the transistor into slight conduction perhaps by adding a very high value resistor between the base and the collector e.g talking about 1-6Megaohms. You will probably have to experiment to get suitable value. My feeling though is this might make the set up a bit more prone to false triggering. No harm trying I guess.

  4. #14
    Automated Home Legend Paul_B's Avatar
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    Thanks Karam. I think it might just be easier, at least for me, to use the 20-150cm version of the Sharp IR sensor which according to the datasheet will keep above 0.7V to about 1m. - https://www.coolcomponents.co.uk/ir-...0cm-150cm.html Appreciate the advice and it has been a useful exercise.

    Paul

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