Shop OBEX P1 Docs P2 Docs Learn Events
pir sensor output voltage!!! — Parallax Forums

pir sensor output voltage!!!

chingfongkeechingfongkee Posts: 2
edited 2011-03-07 08:04 in Accessories
hi , everyone
i want ask about the question about PIR sensor..
when the pir sensor is sense movement, the output voltage is 3.3V
the output voltage will drops to zero when there is no movement after 3 seconds..
although the jumper position setting already is connect at H position..
anyone can solve this problem to delay the time before when it drops to zero?

Comments

  • kwinnkwinn Posts: 8,697
    edited 2011-03-06 10:47
    The only way to get a longer output time would be to add some external circuit. I would suggest a 555 timer or a latch depending on how long you want the signal to remain high.
  • chingfongkeechingfongkee Posts: 2
    edited 2011-03-06 19:24
    can i really use the timer that is built in microcontroller?
    i'm using this PIR for automatic lighting inside a classroom..
    but if im using the timer to set the time period, after the time period when there is still no movement in classroom, the light will automatic off.
  • Mike GreenMike Green Posts: 23,101
    edited 2011-03-06 19:36
    As kwinn mentioned, you would have to add some kind of external timer to get the kind of behavior you want. I don't remember whether the PIR sensor has a microcontroller on it. Even if it does, there's no way to access the internals of it.
  • kwinnkwinn Posts: 8,697
    edited 2011-03-07 08:04
    chingfongkee, for this type of application a very small microcontroller is normally used. A possible alternative is a cmos version of the 555 timer that can be set up for a long time delay.
Sign In or Register to comment.