Microwave Occupancy Sensor

Hi,

I've got a client who wants an occupancy sensor that will work on heat rather than movement so as soon as his children leave their bedrooms it will realise this and turn the lights off.

http://www.cpelectronics.co.uk/ener...sors/ceiling-mounted-microwave-detectors/mws6

Would this work in conjunction with the Cbus L5504AUX 4 Channel Auxiliary Input Unit?

Thanks
Mike

 

I assume you are after a sensor that knows if a person is in a room but not moving. Neither a PIR nor Microwave sensor will do this. Both detect movement. I am not aware of any sensor that will do what you want. Apart from that, if your client really wants a sensor that works on heat a microwave sensor doesn't really fit the specs does it?

 

Yes it will work fine.

I would use the MWS6-PRM-VFC-LV - Ceiling mounted Microwave pres/abs detector + volt free contact 12-24V AC/DC.

"This unit provides an isolated voltage free contact output."

Using the change over contact wired directly into a channel of the Aux input will work fine. As to how well the unit works - I will not comment on as I have never used one.

As with anything that is not tested directly against each system, you run the risk of small issues that are not obvious on paper/manuals and testing is required to gain a degree of confidence. Things like contact closure time on the unit. Is that a long press, short press or bell function. You need to evaluate how C-Bus will deal with the units commands and timing.

I think it will be a bell press.

 

Totally agree, the amount of times I have had this discussion with people...

You can do it with a microwave mass sensor or a ultrasonic/IR laser scanner. But again for this purpose it wont work, because the 'background' always has to be stable, for example a kid brings their backpack in to the room and dumps it on the floor, the sensor wont know the difference.

You can get sensors that get pretty accurate using multiple methods, but you will still get many false trips. The only way I have seen it done 'almost' properly is camera and some pretty sophisticated software that recognizes changes and ect.

 

Actually to be pedantic, nothing emits heat. Heat can be conducted or convected but never emitted. Infrared radiation is emited from bodies and that is what the sensor is sensitive to.

Not withstanding that though, the end result is that you can't easily (or even hardly!) detect a motionless body.

 

MxAnalytics

Hi,

I agree with most people above: Most means of detecting non-moving occupancy will most likely be impractical and/or error-prone in a home environment.

One interesting possibility using IP cameras is discussed below. This approach does not rely on any image analysis being performed anywhere other than within the camera. However this approach would also not be ideal for the above application.

Down-looking ceiling mounted Mobotix IP cameras with recent firmware (MX-V4.3.4.83 or higher) now have a within-camera capability to perform directionally sensitive detection and counting of moving objects entering/leaving software definable corridors, and to trigger responses that can be integrated with C-Bus home automation (for lighting control, for example).

However, this works best when there is good continuous illumination, and so is better suited to commercial environments rather than a home in which you are trying to turn lights off/on automatically. Even in good illumination, people walking in very close physical proximity to each other may be incorrectly counted, and again this analysis feature is better suited to producing fairly accurate total counts rather than reliably detecting every single person coming and going.

I mention it here anyway, because the feature may be of interest to some forum members. More information on the capabilities and limitations of this in-camera MxAnalytics feature may be found on the below page, on which there is also a link to download a more detailed compact guide pdf:
https://www.mobotix.com/eng_US/Comp...w-Available-In-All-MOBOTIX-Single-Lens-Models

 

I love the idea of using image processing for applications such as occupancy sensing and I think it may also be good for things like machinery guards.
Maybe gates and doors too.

Years ago someone who was developing imaging software told me it would be too expensive for such a mundane task when other sensors already work.

Cheap camera hardware and processing power should make it close to being feasible now days.

Clever software could take it to a much higher level than any beam, IR or microwave sensors.

Seven Elevens could block hoodies and balaclavas at the door, guests could enter premises by numberplate recognition and facial recognition could set off alarms at the daughter's bedroom door

 

smartphone appendage

If your kids are like mine you could use a Bluetooth presence sensor, like Airfy was going to release. Detect if they are in the room (attached to their Bluetooth 4 enabled phone)

 

I was demonstrated a Motorola brand android OS camera running facial recognition on board app, a couple of weeks ago. Quite impressive and responsive with a dozen sample faces to scan.

 

If you're talking about the Motorola Focus cameras then they need a connection to a remote server to actually work properly. There are also significant security flaws with the design of the camera firmware so I'd steer clear of them.