I hope someone here will be able to get me started in the right direction. I'm a noob with Arduino and electronics in general, however I am an adult who is willing to learn on my own. I am hoping to do a couple projects for Halloween using an Arduino and I found several examples of such projects online, so I believe they are both possible and reasonably simple to do. At this point, I'm just looking for some general guidance, mostly concerning can/should I even try such a project, and if yes then what hardware would be most appropriate? I'm not asking for someone to design my project or write my code for me, I'm just looking for a little nudge in the right direction to figure out what I must research, learn, and buy.
Here's project idea #1. "Motion Tracking Skull" I would like to have some kind of light plastic skull or fake head of some kind, I would like to have this head automatically rotate left/right and "track" an unsuspecting trick or treater as they walk by. To do this, I know I need some kind of proximity sensor as well as a servo of some kind (right?). I am familiar with two kinds of proximity sensors for Arduino, the HC-SR04 Ultrasonics, and the HC-SR501 IR sensors. Would one be more appropriate for my needs than the other? Would there be something else to consider?
I have a very small SG90 servo now, and although it might work to move a very light skull, I think it would be too small. What is the next size up in servos from this one? I'd like it to be a quiet and smooth moving as possible.
With all my projects, I'd like to include spooky sound effects. This does not have to be premium sound, but I'd like more punch than a tiny clock radio speaker or similar. I have a couple pairs of old desktop computer speakers. What would be an easy way to get the Arduino able to output sound to these kids of speakers?
And I should have mentioned, I'd really like some cool LED lighting effects as well, I'm thinking a neopixel LED inside the skull, maybe?
Idea #2. I would like to do an automated Spooky Witch's Cauldron, I have a big black plastic cauldron now, I'd like to have some LED lights (neopixel?), sounds, etc. I'd like it to start out somewhat harmless and inviting, and then as the kids get closer to it I'd like it to "react" and get "angry" with corresponding lighting and sound effects. Some bubbly, smoky brew inside the cauldron would be amazing, but perhaps that can just be low tech dry ice (if I can find some) or a small fog machine.
Idea #3. I'd like to do a "Monster in a box", basically just a simple pallet wood crate, decorated with "Caution" and "Danger" etc, with maybe some rope and/or chain securing the box. It would sit idle until people got close enough, then the "Monster" in the box would "awaken", making all kinds of growing and snarling noises, and would actually shake the whole crate. I saw more than one example of how to make such a box shake, and I thought the easiest way would be to use a old 12v automobile windshield wiper motor and a custom made cog. This can be setup to make the box jump like crazy when the motor is running. I would just need a little help getting the Arduino to control the wiper motor, but I think that would be little more than a simple relay switch, 12v power to the motor, and some kind of proximity sensor, correct?
I know that's a lot of info, but if anyone has any thoughts or ideas on how I can best get going on this, I'd really appreciate it! Thank you for your help!