Review: RCWL-0516 microwave radar sensor
I was made aware of this super cool radar movement detector a couple of months back from a guy that uses them as an alternative to light switches. With a light sensor and a simple delay, these sensors can control the switching of light when detecting movement. BUT that is not the most impressive feature of this sensor – because it is radar it can be placed behind all kinds of material like wood and ceiling boards and it will still work perfectly in detecting movement.
Just imagine, the unit is inside your roof and out of sight (the radar waves goes through the ceiling board without any problem). With a little bit of modification, you can hook it up to your alarm system as well. Now you not just have light control but also a super motion sensor for your alarm system that will detect intrusion in a room as well inside the ceiling of your roof!
These rcwl 0516 modules are really cheap, we have them available here.
I really like these units, you can connect them to a microcontroller digital pin or let them work all on their own. Yes, there are enough amps to drive an LED and/or a buzzer, adding a relay board (with a transistor to switch a relay) you can switch all kinds of equipment when movement is detected. Introducing a timer IC like a 555 will add delays to it.
Of cause, the jackpot will be a microcontroller like an Arduino (probably a bit of an overkill), even an Arduino Skeleton board might be an overkill but they are much smaller and cost less than half the price of an Uno.
It is a very easy unit to work with:
- It’s got 2 power pins that you can supply anything from5V DC to 20V DC.
- Then it got a TTL (signal pin) that is 0V if no changes are the environment is detected and 3.3V when changes are detected. If you are going to use a microcontroller you simply connect this pin to a digital input pin to monitor if the signal goes high and then programmatically do something if it does. The 3.3V signal is big enough to make an Arduino 5V pin go high as well. (You do not even need a microcontroller, there is enough power from the Sonar signal pin to drive a buzzer and LED)
- It got a dedicated 3.3V Out pin to drive some other boards
- A pdw pin. If you solder an LDR (light sensor) on the board you will get the output from the LDR on this pin. I have not tried it but you should be able to connect a resistor between the LDR pin TTL pin to keep the signal pin at 0V while there is daylight, making light control much easier.
The principle behind this sensor is simple, yet effective. It will send out RF signals in all directions and build up an electronic “picture” of the area from the signals that bounce back. This will continue happening until the “picture” changes that mean the signals bounce back differently. These changes happen because some object reflects it differently because it moved or entered the area. At this point, it will make the TTL line goes high and this new “picture” will now be stored. More movement and this new picture will be different and the same thing will happen.
Radar is used to detect metal and water. It will thus detect anything, like human bodies, that contain water. It will not detect movement of curtains for example, but don’t think it will not detect a human being that hides behind a curtain – it will.
This video below answers many questions on the tech itself:
|3V3||3.3V regulated output. Max 100mA (?)|
|OUT||Trigger: high (3.3V) if motion detected. 0V normally.|
|VIN||4 – 28V supply voltage|
|CDS||(light sensor related.. TODO)|
RCWL-0516 sensor Application
This unit has much application in the security industry.
- it works on true motion, not heat, in fact, heat lights and so on have no effect on the sensor
- In my opinion the most important future, it can be used behind doors, boxes and so on. It can be hidden in cupboards and many places where it can not be seen to tamper with, including in the ceiling of your house.
- it is omnidirectional so it gets the signals back in front and behind the sensor. It thus detects 5 meters in front and behind the sensor. Having this sensor on your ceiling will not just detect movement in the room but also the roof that is a favourite entry point for burglars.
Other applications coming to mind:
- With the use of a day-night sensor and a timing circuit to keep the lights on, say for 10 minutes, after no movement is detected you can kiss your light switches goodbye. It will switch your lights on when you enter the room and off when no one is in the room – no worries about forgetting to switch lights off anymore.
- Toys that do something cool when movement is detected.
- Advertising displays that do something striking when somebody is near them.
Well, you are limited only by your imagination if you want “something” to happen when a person or anything else is moving.
These RCWL-0516 microwave radar sensor modules are available here