Knock something over with a waving machine
Build a simple waving machine from a small motor, battery, craft sticks, and an arm to gently knock over a cup or domino.
Step-by-step guide to build a waving machine to knock over a cup or domino
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Step 1
Gather all materials and set them on a clean table so everything is easy to reach.
Step 2
Bend the paper clip into an "L" shape with a short arm about 1 cm long to make a little crank.
Step 3
Wrap the long end of the bent paper clip around the motor shaft and tape it tightly so the clip turns with the shaft.
Step 4
Tape one end of a craft stick to the short arm of the paper clip so the stick becomes the waving arm.
Step 5
Make a flat base by taping three craft sticks side by side into a straight panel.
Step 6
Tape the motor to the base with the waving arm pointing off the edge so it has room to move.
Step 7
Tape the battery holder to the base and leave the AA battery out for now.
Step 8
Connect the two battery holder wires to the two motor terminals by twisting or taping the wires securely to the terminals.
Step 9
Put the AA battery into the battery holder and watch the arm spin and wave.
Step 10
Place the paper cup or a domino near the arm and gently move it until the arm knocks it over on a soft tap.
Step 11
Remove the battery before making any adjustments to the arm length or paper clip position to avoid surprises.
Step 12
Share your finished waving machine and a picture or video of it knocking over the cup or domino on DIY.org.
Final steps
You're almost there! Complete all the steps, bring your creation to life, post it, and conquer the challenge!
Help!?
What can I use if I can't find a paper clip, motor, or battery holder?
If you don't have a paper clip, use a short stiff wire from a twist-tie or a small nail for the crank, and if you can't find the specific motor or battery holder in the instructions, substitute a small 3V hobby motor plus a coin-cell motor holder or a USB mini-motor and secure it and its power source to the base exactly as the steps describe.
My waving arm only jitters or won't turn — what should I check to fix it?
Check that the paper clip crank is taped tightly to the motor shaft, that the two battery holder wires are securely connected to the motor terminals, the AA battery is inserted with the correct polarity, and the waving arm has room off the edge of the base to move as directed in the steps.
How can I adapt this activity for different age groups?
For younger kids have an adult pre-bend the paper clip, tape the motor and battery holder to the base for them, and use a large paper cup as the target, while older kids can bend the clip themselves, experiment with shorter or longer craft-stick arms from the instructions, or add a switch between the battery holder wires and motor.
How can we enhance or personalize the waving machine to make it stronger or more fun?
Make the arm stronger by taping a paper or cardboard paddle to the craft stick from the waving-arm step, lengthen the lever with extra craft sticks taped together on the base, and decorate the base before sharing a picture or video of the improved machine knocking over the cup or domino on DIY.org.
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Facts about basic electronics for kids
🔋 A single AA battery can power a small hobby motor for minutes to hours depending on load — perfect for short knock-over challenges.
🪵 Popsicle and craft sticks are usually made of birch — a light, strong wood that's great for building arms and levers.
🤖 Rube Goldberg drew silly, complicated machines to do simple tasks — he even won the Pulitzer Prize for cartooning in 1948.
🧲 Tiny hobby motors can spin over 10,000 RPM — that high speed helps even a small motor make a strong waving motion when paired with an off-center weight.
🎯 Using a longer arm (lever) multiplies a motor's push, so a weak motor can still topple a cup or domino.
How do I build a simple waving machine that gently knocks over a cup or domino?
What materials do I need to build a waving machine with a small motor and craft sticks?
What ages is this waving machine activity suitable for?
What safety precautions should I take when kids build and use a waving machine?
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