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Weekly Recap - PIR SensorsJuly 3, 2015

A couple of weeks ago we were talking about Infrared projects with Arduino. Today we bring you some IR related hacks, this time with PIR Motion Sensors: a couple of security applications and an energy-saving project.

Motion Sensing Water Gun

Now this is not the usual home security system. Ashish made a motion detector that sprays water on the intruder, and after that, to embarrass him/her a little bit more it takes a picture and uploads it to twitter.

First thing he needed was a motorized water gun. He opened it and soldered two long pieces of wire. It has a motorized pump and he's using a MOSFET to drive it. A Lightblue Bean, an Arduino-compatible microcontroller board that is wirelessly programmed over Bluetooth Low Energy, controls the water gun and reads the signal from a PIR motion sensor.

BLE_water_gun

When the PIR sensor detects an intruder it sends a signal to the Bean, then the Bean switches on the MOSFET to turn on the water gun. The Bean is connected via Bluetooth with a computer, then with Node-RED it monitors the Bean serial and, if the PIR sends the signal, a Python script takes a picture and a second script uploads the photo to the twitter account.

Don't forget to check their Twitter account.

Posted on Instructables, via Hackaday.

Raspberry Pi Motion Sensitive Camera

RPi_Camera2

This is another security camera project, but this time is built around a Raspberry Pi. Bruce made this camera to keep track of what his cats are up to when he's not home. To do so, he used, apart from the Raspberry Pi, a Raspberry camera module, a PIR motion sensor and a USB WiFi adapter, and he made a wooden case himself with a laser cutter.

When the Raspberry Pi is switched on it runs a Python program that checks the PIR sensor signal to detect motion.

If the PIR detects something moving the camera takes a photo or records a short video, then it is uploaded to a DropBox account, so the user can see it in any device.

Another Python program monitors a shutdown switch on the camera and controls an LED that indicates when the camera is running.

Also, it blinks and stops the software when the switch is pressed and after that the LED turns off to indicate you can unplug the camera. The camera is mounted on a tripod and powered with a USB AC adapter.

Check the complete project on Instructables.

PIR Motion Sensor Lighting

After all this security projects, here's one that might be helpful to save energy. Steve used an Arduino and a PIR sensor to detect motion. The idea is that the lights turn on automatically when you walk into a room, and when you leave they turn off after a little while.

Apart from the PIR sensor, he used a solid state relay. This SSR is needed to control the power of the lighting appliance and isolate the AC load from the Arduino.

9212_pir_sensor

He also included a manual switch to override the PIR sensor. A SPTD switch is connected to 5V, and to the Arduino pins 11 and 12 so it can manually turn on and off the light.

The program is continuously reading the PIR sensor and, depending on the SPTD switch, it turns on or off the lights. This is a clever yet simple way to hack a home appliance that makes use of some common and cheap components.

Check the complete project on Instructables.

Visit Steve's blog: Arduinotronics.

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