Let's just call this thing, "the device", OK?

This device controls up and down movement of tennis balls hung in a garage for parking cars in just the right spot. This allows the balls to be retracted out of the way when there is no car present in the garage/parking spot. It also keeps the little ones from practicing their tennis / baseball skills on it while there is no car. I decided to do this after having walked into said tennis ball while car was not present.

1. When powered on, the user will be prompted to press the [Set] button to start the homing operation for each ball, pulling them up until the limit switch is hit. Then, they lower a little to back off of the switch. NOTE: If you only have a single garage door or car position, you can stop the homing operation of the empty position by pressing the limit switch with your finger (until I get around to improving the software).
2. After the homing operation is performed, the device will check the EEPROM on the Arduino to determine if it has already been set (saved the duration that each motor should run). If there is no indication of a previous run in EEPROM the buttons will prompt the user to press the [Set] button.
3. The setting operation is as follows:
   3a. Press [Set]
   3b. Tap the button for the position that you want to set
   3c. The selected position will run through the homing operation to return it to its home point.
   3d. The user is prompted to hold the button until the ball reaches the desired height. Note: It is OK if the ball overshoots a little, as the code was written to account for a slight delay in human response time.
   3e. Once the desired height is achieved, and the user has released the button, they will be prompted to tap [Set] to complete the operation, or the opposite position's button to cancel the operation.
   3f. Once [Set] has been pressed, the user will be prompted to Tap the position they just set to start complete the operation, which will result in the ball returning to the home position.
4. Normal operation of the tennis balls is as prompted on the buttons: Tap for Up or Tap for Down

I DO PLAN TO PROVIDE AN EXPLODED VIEW SOON.

MATERIAL:

POWER - While the device will run off of a 9V battery, it is recommended that an AC power adapter be used to ensure a consistent power supply. A standard breadboard power supply is used to provide clean power to the device.

ARDUINO SKETCH - https://github.com/somerandomguy03/GarageParkingBallHoist

STAND OFFS - Nylon M2x10mm and associated nut/screw hardware.

SCREWS - Assorted variety of metal M2 and M3

MOUNT FOR BUTTONS - 2x8cm double-sided PCB

MOUNT FOR ARDUINO, L239D, POWER SUPPLY - 5x7cm double-sided PCB

BUTTONS - 6x6x5 mm push buttons (came with my arduino kit)

L239D (used what came with my Arduino kit)

MULTIPLEXER - Adafruit TCA9548A I2C

DISPLAYS - SSD1306 128 x 32 OLED (I used white display color)

LED - https://www.amazon.com/gp/product/B01NAHYUBD/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1. (Careful, mine came wired backwards)

MOTORS - 3V-6V TT Motor

LIMIT SWITCH - KW12-3 Roller Lever Arm Micro Limit Switch, Normally Open and Close Dimension: 20 x 10.5 x 6.5mm (L x W x H)

LINE - As you can see in the pictures, I used both a standard kite string and a monofilament fishing line (60LB/27.2kg, Dia:0.030in/0.76mm, Length: 235yd/214m, Color: Clear). They both work. Personally, I prefer using the monofilament fishing line because it does not unravel like the kite string and get caught on burrs left behind from printing the motor spools. The monofilament was a pain in the butt for clamping on the limit switch plunger, so I just ended up using hot glue, which as worked quite well.

THE BLUE MASKING TAPE YOU SEE IN THE PICTURES - This is simply to cover up the LEDs on the Arduino and power supply because I didn't like how it glowed through the face plate. This is totally optional and you could use whatever you want to block that light.

GORILLA GLUE - This is used to glue the display buttons and set button together.

PULLEYS (IDLERS) - 3mm Bore 6mm Width Timing Pulley Wheel Aluminum.. you need two.

Portions of this code, particularly for the SSD1306 displays and TCA9548A multiplexer were derived from the DroneBot Workshop: https://dronebotworkshop.com/multiple-i2c-bus/

Side note:
Could this have been done with stepper motors? (i.e., not timed) Yes! Howevever, we're
talking about parking a car in a garage, we don't need pinpoint accuracy (at least you shouldn't)! If you are really picky, you could get hooks with a longer threaded shaft that you can use to fine tune the ball's position when down. The professional developers are already rolling their eyes and sighing and we haven't even gotten to the actual code yet. To be fair, I thought about stepper motors after I had already made a bit of progress on this project. And while I'm aware of the sunken cost fallacy and blah blah blah, I am human and decided,I can do some mental gymnastics to justify my lesser design solution. So there!

Most of all, I hope you have fun with this project! I wouldn't publish it if it didn't work! Also,
as stated earlier, updates are planned.