I have a driveway that is over 300 feet long and it is nice to have some advance notice that someone is driving or walking in. Previously, I have used a very expensive IR beam-break detector. It gave a lot of false alarms and eventually failed due to a lightning strike. It also required that I run a very long cable that could survive outdoors, which added more expense. It’s time to switch to a wireless sensor.
I found this inexpensive one at Harbor Freight ($17 with coupon.) It is a simple, stand-alone alarm with a receiver that just flashes some LEDs and emits a tone. It claims to work up to 400 feet and I verified that it works to at least 350 feet, which is good enough for my application. I created the circuit described below to interface this to my Raspberry Pi based home alarm system.
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Make a robot friend with Adafruit’s CRICKIT – A Creative Robotics & Interactive Construction Kit. It’s an add-on to our popular Circuit Playground Express, FEATHER and other platforms to make and program robots with CircuitPython, MakeCode, and Arduino. Start controlling motors, servos, solenoids. You also get signal pins, capacitive touch sensors, a NeoPixel driver and amplified speaker output. It complements & extends your boards so you can still use all the goodies on the microcontroller, now you have a robotics playground as well.