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Microwave sensors

  1. Jul 5, 2009 #1
    I have four dual technology (alarm type microwave & pir) sensors, which I would like to wire up as motion sensors that operate a light or buzzer only during the period of detection. The sensors are Rokonet brand, model RK815DT, which display three frontal leds: m/wave, pir, alarm trigger. They operate on 9 to 16V regulated, 19mA at 12V.

    I gather that the normally closed output connections are meant to latch and trigger an alarm system when both microwave and pir are at a certain state, but I have no idea how to - even if - the output connection can be changed around or the indicator lights be utilised to light up, say, at the rear of the units or power an external led or buzzer.
  2. jcsd
  3. Jul 5, 2009 #2


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    How are you supposed to reset the latched state to clear the alarm?
  4. Jul 5, 2009 #3
    http://www.alertelectrical.com/Burglar-Intruder-Alarm-Systems/Burglar-Alarm-PIRs-And-Detectors/Rokonet-Burglar-Alarm-PIR-Detectors/Rokonet-RK815DT-IWISE-15m-Technology-PIR-RK815DTD3.asp [Broken]

    It looks to me the contacts are normally closed for good reason. It prevents anyone from deactivating it by cutting the wires. The above link suggests that the PIR and uW sensors are Anded to prevent false alarms. Once triggered the output opens for a period of 2.2 seconds min.

    If you want to detect only when both detectors are activated and shut off as soon as the object moves out of range, you probably need to find and and tap into the input of the timer.
    Last edited by a moderator: May 4, 2017
  5. Jul 5, 2009 #4
    negitron, thanks for the response. I have only a very basic knowledge of electronics.

    The sensors are not intended to be incorporated as a proper alarm, but merely to detect and alert to movement in a defined area by momentarily lighting a lamp or sounding a buzzer, and then to go quiet when movement ceases. The pir need not even be operational; the microwave would be sufficient.

    The question comes about from my wish to detect human and animal activity outside the house without using (or needing) a full-on alarm sysytem. The sensors I have are spare and I would like to use them. I have a very old Philips gunn diode device which makes a relay click on and off, which ticked away one night on the back verandah when a carpet python was crawling over it.
  6. Jul 5, 2009 #5
    skeptic2, thank you for your response. I looked at the alertelectrical site you offered, which seems to deal with these sensors as they would be used in a proper intruder alarm system. The Rokonet sensors I have display three lateral leds of different colours. When powered up the sensor will detect m/wave on the left, pir on the right, and centre when both sensors are detecting together. Take away the motion and source of ir and they both switch off, ready for the next movement or ir change. This is what I want the thing to do, but with a more visible light and/or a mild audible alert.
  7. Jul 5, 2009 #6


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    In that case, I'd just crack the thing open and wire the LEDs to the gates of some FETs and have those drive whatever sort of alarm indications you need.
  8. Jul 6, 2009 #7
    Thanks, negitron, at least I now know what a FET is, having looked it up. It also looks like I'll have to find a friend who knows how to crack things open and wire things up. Thanks.
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