For all of you Harry Potter and Quidditch fans out there, haven't you really wanted to have a working golden snitch in your hand? Well, make this "prop" that seems to come alive with a few simple components. This is a great project for kids to learn about basic electronic circuits. Depending how you hold it, the tilt sensor switch will complete the circuit to power up the motors. You can also practice your soldering skills or learn how to solder if needed.
CAUTION: Small objects can be choking hazards. Do not take internally.
Step 1: Little Bits...
You will need:
a ping pong ball or other similar hollow sphere
some cellophane or clear tape to cover the wings
metallic gold paint, spray paint meant for all surfaces is probably ideal but use whatever you have
for the electronics:
coin cell battery (3 volt CR2032 Lithium, also used for LED throwies)
coin cell battery holder
two small vibration motors, the tiny ones that are used in cellphones or paging devices (they are regular motors with small weights attached to the shafts. Since the weight is offset a little, it causes the motor to spin out of balance. When it spins real fast, you get that vibration effect.) Regular motors would do but I used these because they are so small.
tilt sensor switch, this is an electronic component that is essentially a tube holding a small metal bead. At one end are the two contacts that are exposed inside. If the tube is oriented in the correct position, the metal bead will rest on the two leads completing the circuit. It has been called the "poor man's accelerometer." A rather ingenious device used to detect motion or orientation.
You will also need to do a small amount of soldering to put the simple circuit together.
Learn how to solder, it is fun but do it safe.
Step 2: Build the Little Bugger...
Take your ping pong ball and cut out an access panel or hatch for our circuitry.
You can use tape to create a hinge for the piece you cut away.
I have made a quick circuit schematic with Fritzing (open source, free software fritzing.org) Play around with connecting the parts on your virtual breadboard.
On top of the ball, figure out where you want to place the motors where the wings stick out. Cut an X with your utility knife at those spots. You can then press in with your needlenose pliers or the tip of a pen/marker to enlarge the hole.
Since it is easier to feed the wires through first and then solder the components, cut pieces of wire for your wiring harness. I used some ribbon cable since it is pretty flexible.
This is a basic circuit of the battery connected to a switch and then to the motor. Since we are using two motors, they will be hooked up in parallel.
The trick to wiring small components is to pre-tin the wire ends. On the main wires I made a small loop to hold a tiny blob of solder. That way, I could just heat that up and embed the end of the wire from the pager motor.
I used masking tape to insulate any exposed wire from shorting out when it is stuffed back into the ball. The tape also acts as a strain relief for the fragile soldered joints.
Put the battery in to check that everything works. Get a feel for how that tilt sensor switch works and which way it should be oriented.
Step 3: Earn a Set of Wings...
Since these tiny pager motors do not have a lot of torque(force to spin), we will just be using tape to make the wings.
I had experimented earlier with trying to make the wings out of some very thin gold jewelry wire and tape but it was too heavy for the motor to spin. Also on a test circuit, in trying to solder the wire to the weight on the shaft, the heat might have damaged the motor or the additional weight of the solder was just too much.
Build up pieces of tape. Start by securing a piece of tape tightly wrapped around the motor weight. Add more tape to make a stiffer rib. You can then use a sharp pair of scissors to cut the feathers and shape the wing.
Test as you go along to see that the tape does not interfere with the rotation of the motor shaft or if it is too heavy.
These pager motors had a rubber sheath around the motor. It helped with the friction fit of the motors in the mounting holes but I wanted it to be permanent so I removed them and hot glued the motors in place.
Step 4: All That Glitters Is Gold...
Use a gelled fabric paint to make your 3 dimensional designs on the ball. The bottle has a needle applicatior so all you do is paint on your design and let it dry. Customize the golden snitch to your liking. Go Team Adafruit.
Since the ball was smooth plastic, I actually gave it a quick coat all over with mod-podge to act as paint primer.
Paint the ball with a metallic gold color. I used acrylic paint.
When dry, you can pack the innards.
Put the battery in the holder and orient the tilt sensor switch in the golden snitch.
The cover for the opening should fit back in the ball. You can tape that in place if needed.
For a real fancy golden snitch, you can add an on-off switch so you don't have to hassle with taking the battery out if you leave it around for a long time or don't want it to operate when you pack it somewhere.
There is plenty of room left in the ball for LEDs. Look up any "LED calculator" to figure out what resistor to use so the LED does not burn out.
Make a motorized golden snitch and have fun.
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