RCWL-0516 (timed) false triggers

I am using a RCWL-0516 microwave sensor connected to wemos d1 mini (pin D6) and experiencing so really strange false triggers.

See the list below for last nights trail

2019-06-23 05:44:57
2019-06-23 04:44:48
2019-06-23 04:36:14
2019-06-23 04:06:51
2019-06-23 03:36:51
2019-06-23 03:28:20
2019-06-23 03:06:51
2019-06-23 02:36:51
2019-06-23 02:06:50
2019-06-23 01:43:00
2019-06-23 01:36:50
2019-06-23 01:06:50
2019-06-23 00:41:25
2019-06-23 00:41:03
2019-06-23 00:36:50
2019-06-23 00:06:50
2019-06-22 23:40:48
2019-06-22 23:36:50

It seems that (for the occasional false trigger) it triggered exactly every 30 minutes at 06 & 36 past the hour??!! but only for a certain period (between 00:06 and 04:36).

I have separated the sensor from the wemos (about 1.5m/5ft) and have no other strong RF devices nearby.

Can anyone think of a cause??

Post your complete circuit.

Do you have any power supply decoupling - preferably a pi filter - for the RCWL's power supply?

Would be good if you could post your code as well.

The code is nothing spectacular, just looking for a High / Low of the D6 Pin.

No there is no filter, just a condensator at the 5v/gnd at the sensor side. The power supply is a (standard) 1A USB power supply. Nothing else connected to it except the wemos/rwcl-0519

I doubt if it would be a decoupling issue, as the triggers happend exactly (on the second!) at a 30min interval (except for one or two irregular ones).

Schematic is Attached

These cheap sensors are crazy sensitive, that I learned from playing with them and reading about it.

Random triggers: maybe a bird flew by. It'll see this. Or the neighbour's cat. Can be anything, it may be a real trigger of something you didn't see.

The :06 and :36 - go have a very good survey of the space within about 12m radius (in all three dimensions!) on what happens there twice an hour. A cuckcoo clock maybe? Equipment switching power on or off? Just about anything that moves and reflects 6 MHz or so radio waves (e.g. the weights of that clock), forgot the actual frequency but it's thereabouts, can trigger this sensor. The exact timing does point towards something like a clock, after all "it's like clockwork".

You write there are no strong RF sources in your neighborhood. I found this: " I found a carrier at 3.181GHz on my unit using a HackRF One SDR radio".

DO you have remotely read power meter, water meter, natural gas meter? They all consolidate communications to a central device using this sort of frequency, and would all be working on a timed schedule.


Ah yes the GHz range that thing is working at. GitHub - jdesbonnet/RCWL-0516: Information about RCWL-0516 microwave proximity switch module (ICStation.com SKU 10630)

Birds, pets etc are not applicable. There is none of these around :wink: Live in an apartment on 7th floor, with 30cm of concrete walls between myself and the neighbours, so that is also not the issue.

I changed the cable to a shielded one, and moved the sensor to another location. The timed occurrences are gone, but I still get about 1 false trigger every hour or 2. The sensor is still about 1 - 1.5m away from the wemos module...

Not really sure what to do with it.. it's not reliable this way

Birds, pets etc are not applicable. There is none of these around :wink: Live in an apartment on 7th floor, with 30cm of concrete walls between myself and the neighbours, so that is also not the issue.

Don't jump to conclusions that quickly. Unless there's sufficient steel in those walls, this type of sensor may sense right though it.

There is plenty of steel in these buildings.

Nevertheless I am giving up, just had another trail while away from home, and is was constantly triggering.
This sensor does not work for me for whatever reason.

Thanks all for the input

It probably just works too well :slight_smile: Too much activity in your building. Neighbours above and below, people walking through the corridor, birds flying by - all this can cause the sensor to trigger.

One other thing you can do is limit the range, add a resistor to the R-GN pads.