You can do so many different cool projects with an Arduino microcontroller, it’s hard to know where to start once you’ve mastered the basics.  To help with that, I’ve brought together some of my favorite projects. I’ve completed some of them, and other I have on my Arduino bucket list. Let’s start with a project that can make Halloween even more exciting for kids that walk up to your home trick or treating!

Arduino Halloween Props – Animated Halloween props are fun, but when you buy props at the dollar store, you come face to face with some serious limitations.  Because each prop is activated by its own sensor it’s difficult to get them to work together. “If the props are out of sync, the overall effect isn’t as scary.”  The second problem is that that the built-in “motion sensors” don’t work well. This project by Jason Smith lets you control all your animated Halloween props with an Arduino device, and lets you choreograph how and when each prop will turn on and off.  Link to the project: https://goo.gl/DqJQjg

Twitter World Mood Light – This mood light project searches Twitter for emotional content, and then collates the tweets for each emotion, does some math, and then fades the color of the LED to reflect the current World Mood. Red for anger, yellow for happy, pink for love, white for fear, green for envy, orange for a surprise, and blue for sadness. “If an unexpectedly high number of tweets of a particular emotion are found, then the LED will flash to alert us to the possibility of a world event that has caused this unusually strong emotional reaction. Link to the project: https://goo.gl/UsfdeH

Motion Sensor Alarm – When this project detects motion it sets off a light and sound an alarm for all to hear. “This Arduino alarm is handy for booby traps and practical jokes, and it’s just what you’ll need to detect a zombie invasion! Plus, it’s all built on a breadboard, so no soldering required!” Link to the project: https://goo.gl/rD9tqz

Reverse Geocache – Instead of finding a cache using a GPS, your Arduino box won’t open until it is taken to a specific location. “A reverse geocaching box works similar to other geocaching devices.  It will guide you to certain coordinates on earth and instead of finding a geocache located at those coordinates, you carry the box with you, and it opens for you at a predetermined destination.  This is also a great way to do a scavenger hunt (making someone go to multiple locations before the box opens).” Here is an interesting story about how reverse geocaches can be used: https://goo.gl/EFP6GM  Link to the project: https://goo.gl/T3C43G  

Geek Gardening with Arduino – Are you a plant killer like me? You can program your Arduino to automatically water your plants based on moisture content. “An Arduino microcontroller runs my indoor garden, watering the plants only when they’re thirsty, turning on supplemental lights based on how much natural sunlight is received, and alerting me if the temperature drops below a plant-healthy level.” Link to the project: https://goo.gl/V9F5fp  

Arduino Motion Detecting Squirt Gun – “Whether you just want to prank a friend today, or you’re looking for a real solution to keep the cats off the counters or regularly mist the plants, here is a hack that may work for you. An Arduino-powered squirt bottle uses a motion detector to fire rapidly every time there’s some motion in front of it. If you’re trying to keep the cats off the counters, for example, this is the perfect setup to keep in the corner behind the blender so the cats get a quick, harmless spray every time they jump up on it.” Link to the project: https://goo.gl/UjGi7f

Arduino RFID Door Lock – Uses and Arduino, Door lock with solenoid and an RFID reader. “Here we are with the classic RFID door lock. It’s classic in that whole, “We live in the future and take it for granted at this point” sense. In this tutorial, we will set up a door latch that can be opened with the swipe of an RFID Tag! We will program a list of acceptable ‘key’ cards that will unlatch the door for a specified amount of time. This is a really simple project, but it does require that you alter your door jamb, so be prepared to do some wood work if you the strike plate to fit securely and flush.” Links to two different project: https://goo.gl/dSxnrd -or- https://goo.gl/b8DKqg