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Microwave Doppler Radar Motion Sensor

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  • Microwave Doppler Radar Motion Sensor

    I put together a microwave motion sensor and am very happy with the results. It technology is Doppler effect of a moving things that reflect microwaves. Water (body) is a good reflector. Really good if one wants to detect motion in a room or hallway. I do not have pets so not able to assess what it does with smaller critters. It can be hidden behind glass or plastic without affecting sensitivity. It did not sense through my wood and gypsum walls so isolation to specific areas is convenient. It has a range adjustment between 1 and 10 meters and this worked well to zero-in on the specific area for motion of interest.

    It is omni-directional so if it is set at 2 meter, for example, it will sense motion in 3-D space with radius of 2 meters from where the sensor is placed. One could mount them on a ceiling or inside a plastic electrical box with a plastic face plate covering it up. Did not try, but suspect that a metal box may mess up with it's RF.

    I interfaced it with Sonoff Basic because that is what I had in-hand, but other easier methods can be used. I included pictures and text for the Sonoff Basic mods, data sheet, and product links in the last Section of mcsMQTT manual (http://mcsSprinklers.com/mcsMQTT.pdf).

    It has 4 push-down connectors. Two for power. Two for output switch contacts. It was designed to turn on/off lights based upon motion, but anything up to 7 Amps can be switched through it. In my case it was 3.3V/Gnd into a discrete input of ESP8266 in the Sonoff Basic.
    Attached Files

  • #2
    Thank you Michael.

    So the device can be powered from the Sonoff WiFi basic power of 3.3VDC?
    - Pete

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    • #3
      The manual describes the full integration. I used 12VDC wallwart and repurposed the input connector of Sonoff to be 12VDC and Ground. Ran the 12VDC to the input of the 3.3VDC regulator on the Sonoff. Another approach would be to provide mains voltage to both Sonoff and the 12VDC wallwart rather than wallwart only. My junk box did not contain something like an old lamp cord with 120VAC power connector. I have only bigger 3-prong cables that were not practical in this case. The wallwart I used was only rated at 0.2 watt while the radar sensor was rated at 0.5 watt. With both the Sonoff and sensor the wallwart unloaded voltage went from 19VDC to 14VDC so I do not think the sensor is really drawing what is stated in the data sheet.

      I also obtained a few of the microwave motion sensor circuit cards RCWL-0516 which are $1 or less. These run at 4VDC, but not 3.3VDC. There is much about these on the internet. One of the things I picked up about them is there are sensitive to long term power supply fluctuations. The solution is to put a large capacitor on the input power as close as possible to the board.

      RCWL-0516 does not have the pots of the one I implemented for adjusting range. One would need to solder SMT devices to change the characteristics. Too much effort for me just to experiment.

      Attached is info that includes requirements of 1 CM between it and whatever is used to interface it. It shows 3 milliamp operating current so if using something like a pair of AAA or 123 cells the lifetime would be 14 days (1000 mAh/3 mA/24 hr) so not suited for a battery operation.

      If I was interfacing these last year my go-to solution would be a door-window sensor as all that is needed is something that detects a switch closure. Door-window sensors are typically battery powered so in this solution one would need both wired and battery power which is not very attractive in my opinion. Using a 5 VDC pick-off of the Sonoff like I did for the water-flow-sensor will be my first approach when I interface the RCWL-0516.
      Attached Files
      Last edited by Michael McSharry; October 5th, 2018, 01:20 PM.

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      • #4
        Thank you Michael.
        - Pete

        Auto mator
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        • #5
          I wired up the RCWL-0516 and it works fine in initial testing. No cuts to the Sonoff, only solder wires to existing points. Will need to put it somewhere to see how it behaves in a real environment.
          Attached Files

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          • #6
            Thank you Michael. Looking maybe to utilize this device to suppliement or replace the current wired door / doorbell PIRs.
            - Pete

            Auto mator
            Homeseer 3 Pro - 3.0.0.534 (Linux) - Ubuntu 18.04/W7e 64 bit Intel CPU - Mono 5.20
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            • #7
              The original one that was using 12VDC stopped working through the interface. I can see the LED on the sensor report motion triggered, but it is not getting reported via GPIO14 input change. Will need to investigate. The Sonoff is working normally otherwise. The smaller one using 5VDC is working well and actually may be preferred for ease of interface as well as a shorter retrigger period for motion. The 12VDC one has a minimum of 10 second retrigger period.

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              • #8
                Turns out a simple issue. One of the screw terminals was not fully closed down and the wire wiggled out. Secured it and back in business.

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                • #9
                  Thank you Michael.

                  Have pockets around door frame of space that I might install this device ....outside it is brick...

                  Inside door trim ==> wood frame with pockets(door frame spacers) ===> outside brick
                  - Pete

                  Auto mator
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