@Tex: I live in Africa, we have a lot of great things here but secure locations is not one of them. This is a great opportunity to come up with innovative security solutions that the professionals have not considered. Hobby level: tell that to the Wright brothers or any of the plethora of hobbyists who come up with great solutions. "Security Experts" in my opinion are people who tend to be ignorant and unwilling to learn, they call themselves experts because they know everything about their limited knowledge, Henry Ford had many bad things to say about experts in his autobiography. Hobbyists, in my opinion, are much more willing to learn and innovate, which is why you and I love this forum.
Thanks all for your great ideas. Please keep them coming.
You need one of these.
I will in the garage tinkering....
I too had not seen these microwave modules before, and now I've seen them I can see a solution to a specific problem I have.
The low cost of these surprised me. I didn't think even the Chinese could build a waveguide and whatnot for something like radar gun for less than $1, and they don't !. The device works by measuring the disturbance of a GHz continuous radio wave, and as such detects movement, not distance or static objects.
The GHz oscillator uses PCB tracks to make the necessary inductors and capacitors, so it's frequency is neither precise or stable, but that doesn't matter. The original purpose for these modules is controllers for room lighting, so there are lots of them, and they are cheap.
A really cool attribute is that they can be mounted inside a plastic box, with no lens or window needed. Great for hidden detectors.
Here is a write up :
and if you want a different shape :
I've just ordered some !.
Sorry to hear about your problems. I have an acquaintance who is a missionary and also tells me about the exceeding beauty of the African country side and the warmth of its people.....but that theft is rampant.
Anyways, the microwave modules hold a lot of promise. And at that low price, you can utilize many redundant locations.
My concern would be, how do you discriminate against wildlife? I ignore what type of animals roam in the vicinity, but some of them may be large enough to trigger a signal, perhaps?
"Will design analog circuitry for Beer."
I've had one of these doppler modules working for around 6 months now, activating the CCTV camera recording system. They are far less susceptible to false triggering, and have reduced the number of false triggers I get to zero; the CCTV HDR only records real movement, whereas when I had a PIR trigger it would sense gusts of wind. They do need a larger object to trigger them, though, or at least mine does. I have it mounted inside a small IP66 plastic box, and it will trigger at around 5m with a human target, maybe 10m with a vehicle, but never triggers with small animals, like a cat. The PIR used to be triggered by cats all the time.
One down side is that these sensors are omnidirectional, the curious antenna/mixer design seems to produce as strong a field behind the unit as in front. This can be a nuisance, I found, as at first cars driving down the lane behind the sensor would always set it off. The fix was to mount the plastic box on an aluminium plate, to screen the rear of the sensor. This doesn't seem to affect the performance at all, other than to restrict the field of view to a bit greater than a hemisphere.
There are a number of different types around, and the one I'm using has a power mosfet switch. I'm directly switching the power to an 08M2, connected to an HC-12 transceiver, so that when power is applied an alarm signal is transmitted, then the unit waits until an acknowledgement is received (as a handshake confirmation) from the CCTV HDR controller (another 08M2 and HC-12, that switches the record line on the HDR). If no acknowledgement is received the unit continues to transmit alarm signals until the microwave module times out and turns the power off (around 30 secs).
I did some rudimentary testing, they are supposed to be omnidirectional but mine is not, could be because I have it just siting flat on a table in a breadboard. I measured about 1.5 meters on one side and about 3 meters on the other. This is indoors, I suspect outdoors it will be better. I'm having a busy day and will test the current draw later. I suspect it will draw a goodly amount of current since it's meant to be powered from the mains for turning lights off and on. I suspect you can have some screening and aiming in order to only detect taller object so as to discriminate between animals and people.Any idea on the range that these modules work at on humans? At that price I can string them up with lots of redundancy.
Thanks for the great ideas. I have bought 4 of these, waiting for delivery:
LFS-DC04 2.7GHz Microwave Radar Module DC 5V 360 Degree High Level Signal Output