Help help help !!!

Discussion in 'The Projects Forum' started by mirfurq, Jul 2, 2010.

  1. mirfurq

    Thread Starter New Member

    Jul 2, 2010
    hi guys... i am working on a project which basically contians a PIR sensor. Since PIR sensor detects the motion of human in its range it glows a LED and after some time if a human is still inthe range the LED turns off. i want to take signal from this LED. basically i want top make a circuit that a human can manually turn on the TV this ciruit should be connected witha TV. when human wants to watch the TV it will manually turn on but after turning on when PIR detects the absence of human motion i want a delay of 1 minute which is basically be done be using counter i dun want to use 555 timer so after 1 minute delay it will give signal to relay and the relay will turn off my TV.

    please guys i need yur help witht this ciruit i dun know wot to do...
    thank you for that
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    It looks like you need help thinking of titles for you threads.

    What have you done so far? What PIR are you using and are you using a CMOS or standard 555?

    If you are using IR for the action, Do you have the remote control codes for the TV you are working with? You will need to know the IR codes if to turn the TV off.

    Or are you using a relay ov some sort to cut power to the TV?
  3. JoeBro391


    May 15, 2010
    next time you type up something, take your time and maybe proof-read once or twice.

    Anyway, the first part of your circuit is easy. You'd want to have a relay attached between the power ON switch of the tv. This is easier to do with older televisions, but certainly doable with newer ones, if you have decent soldering skills. I'm not too familiar with PIR sensors, but from what I hear, they're not too unlike CDS cells. What you'd want to do is hook one lead of the PIR sensor to Vcc and the other end to the base-lead of a NPN transistor (T1). When the PIR sensor detects IR light, it allows the positive voltage (connected to the transistor's collector) to flow through the transistor, switching it on. Then the collector-emitter current should flow through the coil of a relay, switching the relay on and turning the TV on.

    that's the simple version. But you want it to turn off when everybody leaves the room? There's a problem with that. From what I can tell, the PIR sensor doesn't actually sense Infrared light; instead, it detects the change of infrared light (motion). That means that if you walk into a room and the sensor picks you up, the TV will turn on but if you sit down to watch the TV, it'll turn off after the minute because it's not detecting motion.

    If you still want to do the timer-thingy, then i'd say that the transistor's (T1) emitter to ground and the collector to Pin 2 of a 555 timer this is in monostable mode and wired so that the output goes HIGH for 1 minutes. The output of the 555 timer (Pin 3) is connected to the relay's coil, switching the TV on, every time the PIR sensor detects a change in motion. The only problem with THIS idea is that, the 1 minute won't re-start every time the PIR sensor detects motion; instead the 555 timer will go HIGH for 1 minute, go LOW, AND THEN, once the PIR sensor detects motion again, will the 555 timer go HIGH again and switch the tv on.