Computing stuff tied to the physical world

New PIR motion sensor

In Hardware on Aug 30, 2010 at 00:01

From now on, the Room Board is going to be shipped with a new PIR (passive infrared) motion sensor:

Dsc 1866

The reason I went looking for a replacement is that the ELV unit was out of stock for a long time, especially in quantity. It seems to be back now, but I had already found a good alternative.

The unit shown above is nice for a couple of reasons:

  • it’s equally low-power, drawing 40..50 µA
  • this unit is specifically for 3 .. 3.3V, whereas the ELV unit was running slightly out of spec
    • (it officially requires 5..24V, but the regulator brings that to 3V)
  • it’s slightly lower on the sensor side (and higher on the component side)
  • the sensor seems to be sensitive over a somewhat wider angle
  • it’s no longer a kit, no need to solder-in that sensitive PIR chip anymore

I’ve yet to do some serious testing w.r.t. range, but it appears to be ok.

Here are the two sensors side-by-side:

Dsc 1867

One unfortunate detail is that the pinout is different. Yes, even 3 pins can lead to incompatible variations!

The old sensor has: VCC GND OUT – the new one uses: VCC OUT GND. Besides, I want to connect it to +3V now, i.s.o. PWR.

I solved this by using the other side of the room board, and reconnecting GND slightly differently – i.e. cutting the pin off and rewiring it as follows:

Dsc 1868

It’s a hack, but it works. The two remaining pins are still enough to keep the sensor board firmly in place.


  1. Do you have the datasheet or model number available for the new PIR? Thanks!

  2. JCW,

    can you share with us where you bought this PIR? I still need to get some PIR’s, since the ELV units were out of stock when I wanted to order :)


  3. Is OUT still true/false or is it a “serial”

  4. @Greg – All I have is some simple specs. I’ll add it to the docs page.

    @WWolkers – It’s from a China wholesaler, their minimum order quantity is 100…

    @Mathias – Yes, logic-level. There’s a jumper to set single shot or repetitive pulse.

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