Do you live in an apartment, condominium, or dormitory? Do you want all your neighbors and friends to know how ridiculously geeky you are? Than this project is for you! Basically, this circuit waits for a knock at the door, then turns on an LED in the peephole that lights up the hallway outside. It uses a Parallax Sound Impact Sensor to detect the door knock and a simple analog circuit to hold the LED on for a few seconds after the signal is received from the sound impact sensor. Here’s the schematic:
“Port 4″ is replaced by the sound impact sensor, which can be wired up to it’s respective pins. I used a bright blue LED for mine, and it’s quite effective in getting attention. You will need a simple power converter of your choice to power this circuit, I would suggest a PowerTwig , but you can use just about anything. A resistor could probably suffice. One thing: If you plan to use this project, I strongly recommend powering it either from wall power (if there is an outlet close by) or a rechargable 9V battery. I’ve found that a standard 9V battery only lasts 3 days if continuously powered.
I hope you found this mini-project interesting, I’m working on some bigger things that I’ll post about soon.
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