Bedtime Buddy

A little robotic buddy that helps you get to bed on time by looking sadder and sadder the longer you're awake.

Supplies

Parts

• 1/4-inch thick Lauan Plywood
• Any material will work
• The material is actually 3/16-inch thick
• Need a 6x8 inch piece
• Assorted M2 screws, nuts, and washers
• 2x 16mm screws
• 6x 8mm screws
• 8x M2 washers
• 6x M2 nuts
• 2x SG90 9g Micro Servos
• 1x Arduino Uno
• Other Arduinos also work
• 2x Momentary Button Switches (one is only needed for testing)
• 14x Jumper Wires

Tools

• 3D Printer and filament (this version used PLA)
• Bandsaw or scrollsaw (for cutting the faceplate out of wood)
• Drill (or drill press if you have one)
• 1-1/2-inch hole saw (for drilling out the eyes)
• 1/2-inch drill bit
• 5/64-inch drill bit

Step 1: Cut the Face Out

The dimensions in the drawing are given in millimeters.

1. Use a bandsaw to cut the shape out
2. Use the 1-1/2-inch hole saw to drill out the eyes
3. You can also use a scroll saw for this step (example video: https://youtu.be/iP1kR4ThXuU)
4. Use the 1/2-inch drill bit to drill the two holes for the mouth
5. Use the 5/64-inch drill bit to drill the two small holes between the eyes
6. These are precise. Make sure the holes are not too close together or drilled at an angle. Otherwise, the eyelids will not move smoothly.

Step 2: Make the Mouth

Printing

Print "Mouth.3mf" and print two of "Mouth Holder.3mf".

Do not use support material, it will make the mouth part weaker. Use 30%-99% infill.

I used PLA for all parts, but "Mouth.3mf" may last longer if printed with TPU.

Assembly

1. Stick the posts of the mouth part through the mouth holes.
2. On the back side, for both ends of the mouth, slide a mouth holder down onto the post.
3. There's a screw hole that goes through the holder and the post. Slide an M2x8mm screw through it. (Do not tighten the nut on this screw very hard or you will break the holder part.)

Step 3: Install the Eyelids

Printing

Print "Right Eyelid.3mf", "Left Eyelid.3mf", and "Motor Gear.3mf".

Use supports for the eyelids. The gears attached to the eyelid have an empty space in the middle which prints better with support.

Installing

Now install the screws that the eyelids will pivot on. There is a lot of hardware on these screws, so be careful to keep everything in the right order.

1. Add a washer to an M2x16mm screw
2. Insert the 16mm screw into one of the small holes between the eyes
3. Put a washer and then a nut on the other side and tighten the nut all the way down so the washers are sandwiching the wood. (This will keep the screw rigid without having to tighten the rotating parts too much.)
4. Add another washer to the screw
5. Take one of the eyelid prints and slide it onto the screw through the hole in the gear
6. Make sure the side of the gear with the depression in the center is facing the wood
7. The round edge of the eyelid should be at the top. If it's not, use the other eyelid.
8. You may need to use the 5/64-inch drill bit in the gear hole to make the screw fit
9. Add another washer to the screw
10. Add a nut and tighten it loosely (not enough to clamp the eyelid in place)
11. Add another nut and tighten it down while holding the previous nut in place (this will keep the nuts in place without clamping onto the rotating eyelid too much)
12. Repeat for the other eyelid

The final order of everything on the screw, starting at the screw head is:

washer, wood, washer, nut, washer, eyelid, washer, nut, nut

The eyelid files are named for the side they're on when looking at the front side of the face, so the names may seem backward while you're attaching them.

Step 4: Attach the Mouth Motor

Printing

Print "Mouth Motor Mount.3mf"

Lay the surface with the rectangular hole in it flat in your slicer.

This part does not need support material.

Attaching

Ensure that the mouth moves smoothly before you attach the motor.

Insert one of the 9g servo motors into the rectangular hole of the motor mount.

Put an 8mm screw through both of the motor's mounting holes and use a nut to secure them both.

Check that the servo works, by plugging it into your Arduino. Make sure the motor is at the 0 position before proceeding.

Put the single horn attachment onto the motor shaft.

We're going to glue the hub of the servo horn to the top surface of the right mouth holder (right, when looking at the back side of the face).

Use sandpaper to roughen the bottom surface of the servo horn, and the top surface of the right mouth holder. Super glue will not adhere well if you don't roughen both surfaces.

Roughen the bottom surface of the motor mount too. This will be glued to the back surface of the face.

Make sure that the mouth is in the smiling position and the motor position is set to 14 (you can run "motor_set14.ino" to do this, wiring instructions are in the sketch).

Carefully apply a very small dab of super glue to the top of the right mouth holder. Do not get super glue on the top surface of the mouth post or you will not be able to take the mouth part out.

Apply super glue to the bottom surface of the motor mount.

Align the center of the servo motor hub with the center of the smile holder and press the motor mount down.

Hold it there for at least 20 seconds.

The servo horn should now be glued to the mouth holder.

Step 5: Attach Eyelid Motor Gear

Next, we need to create the gear that will power the eyelids.

Printing

Print "Motor Gear.3mf". You should not need support material.

Assembly

The servos come with horns that have a hub with little teeth that grab onto the output shaft of the motor. Most 3D printers can't print fine enough details to replicate those little teeth, so we will cannibalize the hub of one of the horns to make the motor gear.

1. Take one of the servo horns (doesn't matter which)
2. Use snips or wire cutters to cut off the horn, just leaving the hub
3. Sand off any protrusions so the hub is round enough to fit in the depression in the center of the gear you printed
4. Roughen the outer surface of the hub and the inside surface of the gear depression with sand paper
5. Use a small amount of superglue to seat the gear hub in the center of the gear