Easier Useless Box TowerPro SG90 by blarbles

Last crawled date: 3 years, 1 month ago

I wanted an easier to make Useless Box design that worked without a micro controller. I wanted less parts, construction, and screws. Easier to print parts than existing designs. I used the two remixed sources as a base to redesign the whole thing. I also wanted a paw to push the switch back and "NOPE" in the case top.
What you need

1x Printed Box with battery holder OR no battery holder. If you choose the box without then you will need to use another battery/power solution. My design gets by, but you might prefer to use something else. You can get AAA dual battery holders for cheap in packs of 5, 10+

1x Printed Top-Main with text OR not depending on your preferred appearance
1x Printed Top-Secondary
1x Printed Arm
1x Printed Arm-Paw
(Optional) 1x Printed Nope-Text to insert into text cutout in Top-Main-With-Text
1x Tower Pro SG90 9G Micro Servo (cheap on eBay and Amazon)
1x 6pin On-On Micro Toggle Switch
1x Micro Roller Lever Arm Open Close Limit Switch (KW12-3 PCB Microswitch is what I bought)
2x AAA batteries
Wire
Super Glue
6x M2.5x10 screws
2x M1.6x10 screws (approximate size, this is for the microswitch which has very small screw holes. You could also just superglue the switch)
Solder and soldering gun
Instructions
Modify your Tower Pro SG90 9G Micro Servo
There are lots of complicated instructions out there about soldering resistors and cutting the gear piece that stops it from turning 360. Skip that.
Open the back of the servo
Desolder the wires to the motor and the long wires from the circuit board.
Toss the circuit board
Solder the long wires you reclaimed directly to the motor (see picture)
Screw the back of the servo on
Why don't I need to make the servo go 360? Because the arm is designed to operate within the servo's restricted radius.
WARNING: If you send power to the servo after this mod and the servo has hit its radius limit the servo will heat up and eventually die.
Modify your On-On Micro Toggle Switch (Optional)
Some On-On switches are really stiff. You really have no idea ordering them as far as I can tell. If the servo doesn't have enough torque to push the switch you will need to modify it by bending the the outer casing up and cutting the switch pin down by 2-4 mm. If you get a cheap plastic one then be happy it's not that hard. I got a fancy metal spring one which was a pain to cut.
Connect wiring and Align the Servo with the Arm
Once everything is wired test and the following should happen:
When the On-On switch is back (away from the servo) the servo should spin counter clockwise.
The servo should STOP spinning counter clockwise when the micro lever roller arm is depressed.
When the On-On switch is forward (towards the servo) the servo should spin clockwise.
You will need to get the servo either all the way counter clockwise or very close then pull power. You will use this as your base point for attaching the arm.
The arm should be pressing the micro lever roller arm while turned all the way counter clockwise.
Glue stuff
Glue the paw to the arm.
CAREFULLY put a small amount of superglue in the arm hole that connects to the servo gear. If you put too much you will glue the arm to the motor case or worse. Tighten the screw that comes with the servo. Make sure you have the servo rotated all the way counter clockwise AND the micro lever roller arm is depressed when you finalize the arm position.
(Optional) Glue letters if you used the top with text.