Press the Button, Watch the Battery Spin

Here is a circuit that lies to you. It looks exactly like a normal "press the button, spin the fan" gadget: a fan up top, wires looping around the sides, a chunky button on the front. Hand it to someone, tell them to press the button, and their brain says the fan will spin. It doesn't. Instead, the battery spins.

This summer I decided I wanted to make unique electronics projects, and I wanted to start small to knock the rust off before tackling anything big. But I didn't want to build another boring little fan circuit, so I gave it a twist. I'd seen a video online of a contraption wired up like a totally standard button battery fan setup, except pressing the button spun the battery instead of the fan. I thought it was clever, and I had to build my own.

So that's what this is: a battery powered prank. The fan is fake, the wires are fake, and the only thing that moves when you press the button is a battery riding on a hidden motor underneath. It was a great way to get comfortable with soldering, basic wiring, and a whole pile of little 3D printing tricks for making something look real. The electronics are beginner friendly (it is one switch and one motor), and most of the challenge lives in the fit and finish details, which I'll walk you through, failures and all.

Let's build it.

Skill Level: Beginner. If you can solder three wires and run a 3D printer, you can build this. The tricky parts are patience with tolerances, not electronics.

Time Required: Roughly 4 to 6 hours of active work, plus print time and 24 hours of glue cure time.

Materials (I pulled most of mine out of an old landline phone and other dead electronics; an Elegoo starter kit works just as well):

1. Small DC hobby motor ×1
2. Momentary push button ×1
3. AAA battery ×2-3 for the visible "spinning" battery (mine's a Duracell) and the actual batteries used (I used 2 but you can use 1)
4. Hookup wire, red and black
5. A paper clip (started as the fake fan axle)
6. Scrap filament offcuts (used to build a support cage for the button)

Tools:

1. Soldering iron and solder
2. Hot glue gun/super glue
3. Needle nose pliers
4. Wire cutters and strippers
5. X Acto knife
6. Sandpaper

Software (the modeling tools I used):

1. SolidWorks, for the main case
2. Autodesk Tinkercad, for the fan and the spinning battery holder
3. PrusaSlicer, for slicing and for modeling the simple fake button cap

3D printing:

1. FDM 3D printer, printed in black PLA (I used Sunlu)

When completed the overall size is 3.4" x 2.8" x 2.15"

Before any building, here is the trick, because the whole project is built around selling it.

What people expect: a normal version of this gadget would be wired battery to button to fan, and pressing the button spins the fan.

What actually happens: mine is wired battery to button to motor, and the motor is hidden under the battery case. Press the button and the motor spins the battery.

Everything else is a decoy. The "fan" on top is glued in place and never moves. The red wires looping around the outside aren't connected to anything; they're there to make it look like a real hand wired circuit. The real, working battery is hidden in a slide out tray on the bottom.

The actual electronics couldn't be simpler. It's a single series loop of battery to button to motor. Press the button, the circuit closes, the motor spins.

The process:

1. I did a quick, rough wiring job, not soldered yet, just twisted together, to confirm everything worked before committing.
2. I confirmed the motor spins when the button is pressed.

One thing worth knowing: I did not care which direction the motor spun, so I completely ignored polarity. For a gag like this it makes no difference, which makes wiring even more relaxed.

Note: Always test with a rough, temporary wiring job first. It is a lot less painful to fix a twisted wire than a soldered one.

Here is my first real snag.

What went wrong: when I first wired the button in, pressing it did absolutely nothing. The button was basically dead in the circuit.

The fix: after staring at it for a bit, I realized I'd wired into the wrong terminal of the button. I moved that wire to the other side, and suddenly pressing the button started the motor exactly like it should.

Why this happens: a push button only connects across specific pairs of pins. Wire into the wrong pair and pressing the button never actually closes the circuit. If your button seems to do nothing, this is almost certainly why.

Once the rough circuit proved out, I soldered everything for good. Order didn't really matter, but I started at the motor: motor to one side of the button, the other motor lead to the battery, then the last wire from the battery over to the correct button terminal I'd just figured out.

Tip: Give every joint a gentle tug after it cools. A joint that looks fine but is only lightly tacked will fail later, usually after the case is closed and hard to open.

With the guts working, I moved to making it look like a finished product. I wanted a clean, minimal, 3D printed box specifically so it would read as a real device instead of the cardboard contraptions I'd seen.

I built the main box in SolidWorks.

The process:

1. I measured the glued together battery and motor unit.
2. I created a pocket in the box to hold it, leaving plenty of extra room around it so the wires wouldn't get pinched or bent.
3. I made the bottom of the box not fully solid, leaving a window and channel so the wires had somewhere to route through.

The size for the battery and motor is 2.5" x 1.25" x 1". The size of the wiring and button area is 2.5" x 1.65: x 1". I also made the walls 0.15" in order to provide proper support to the box by reducing the amount of used filament.

Next I added the openings on the top face: a hole for the button, and a small hole for the paper clip that would act as the fake fan's axle.

For the button placement, I set it 1.2 inches from the battery. I picked that by physically spinning a battery around on the motor to see how much clearance it needed.

Honest hindsight: I measured against the bare battery, not the bulkier fake battery holder I designed later, so things ended up tighter than I wanted. If I did it again, I'd push the button noticeably farther from the spinning battery.

Then I designed the bottom of the case. I didn't want components falling out the back, so I added a slide in tray. This is also where the real, hidden power battery lives. The tray got its own slide opening so it clears the motor and doesn't fight with the box cover.

The process:

1. I modeled a tray that slides into the bottom of the box on a rail.
2. I cut a slide opening in the tray so it clears the motor as it goes in.
3. I matched the tray and cover to the box footprint so everything closes up flush.

The fix (later, once I printed it): when the parts actually came off the printer, the cover was too tight to slide on. I sanded it down in both the X and Z directions so it was a touch thinner and narrower. After that it slid on with a satisfying, snug fit.

Once the box was designed I started printing.

What went wrong: my printer's tolerances meant every hole came out too tight for the parts to fit. The button, the motor, and the paper clip just wouldn't go through.

The fix: I widened the holes two ways. For some, I twisted a pair of needle nose pliers through to ream them out. For the trickier ones, I grabbed my soldering iron with a fine tip and melted the openings open to exactly the size I needed. Once everything slid through cleanly, I was back in business.

Tip: A fine tip soldering iron is a surprisingly good "drill" for opening up undersized holes in a print.

Safety note: Melting plastic with a soldering iron gives off fumes. Do it in a ventilated spot with a fan pointing away from you, and wipe the tip afterward.

The next step is to insert the button. Because of how big the box was relative to the button, the button had nothing solid behind it. So when you pressed it, the whole button just sank into the box instead of clicking.

The fix: I built a little support out of scrap filament offcuts, basically a tiny cage inside the box that the button could rest against. That held it at the right height. It still wobbled a bit, so I added a small ring of hot glue around the button to lock it in place. After that it pressed properly every time.

The button I salvaged had a long plunger, which was perfect, because I could cap it with a little silver look box on top to make it read as a proper device button.

The process:

1. I modeled the cap quickly in PrusaSlicer by importing a simple box and subtracting a cylinder from it (a negative volume) to make the socket that sits over the plunger.
2. After printing, I opened the socket up a touch with the soldering iron.
3. I sized that socket with the real batteries installed and powered.

Why this matters: if the cap sat too low, just resting it on would press the plunger and start the motor, exactly what I did not want. So I tuned the depth until the cap sat fully seated without triggering the button, then locked it with a tiny bit of melted plastic so it couldn't wander while still leaving the button free to press.

Now the decoy. I modeled the fan in Tinkercad.

The process:

1. I started with a cylinder for the hub, then sketched a diamond shape for a single blade and gave it some thickness to match the hub.
2. I lined one blade up against the hub, grouped it, then hit Ctrl+D to duplicate and rotated the copy.
3. I'd planned on three blades at 120 degrees apart, but three looked too sparse, so I grouped all three and rotated the whole set by 60 degrees, which gave me six evenly spaced blades.

I didn't sweat the exact sizing in Tinkercad since I could scale it in PrusaSlicer until it looked right, and I skipped modeling an axle hole, figuring I'd just poke one with the soldering iron later.

What went wrong: when I went to fit the fan, it sat too close to the spinning battery. The root cause traces back to Step 7, where I'd planned spacing around the length of the battery rather than the fake battery holder, so several parts ended up crowding the spinning element.

The fix: rather than reprint, I took the easy route and hot glued the fan a bit farther back. Since the fan was always decorative, it no longer needs the paper clip axle at all. It's just glued in place looking pretty.

This is the star of the show, the holder that rides on the motor shaft and makes the battery spin.

The process:

1. I measured the battery and modeled a simple cradle in Tinkercad.
2. To sell the "real metal" look, I added silver accents. which are just thin squares I printed in silver
3. A couple of negative space cubes squared off the top, since the outer edges were still rounded.

What went wrong: the first version had a base that was too short, so the motor shaft didn't seat fully into the holder. It spun off center and wobbly.

The fix: I redesigned it with a taller base so the shaft sits deep inside. Now it spins cleanly and centered.

This is the detail that really sells the lie. I had both red and black wire, and I went with red so the wiring would pop against the black case and look like a deliberately hand wired gadget.

The process:

1. I stripped the wire ends, folded the exposed copper over, and melted a small bulb of solder on the tip so it looks like it was genuinely soldered to a terminal.
2. I used the soldering iron to carve shallow grooves into the box, pressed the wire into them, and shaped the runs by hand.
3. The wires kept popping out, so I ran a bead of hot glue into the grooves and pressed them in for good.
4. I routed the fake loop button to battery to fan to button, making sure the wire never blocks the battery holder from spinning freely.

At the fan, instead of a solder bulb I made the wire look like it disappears through the box (the motor's on the underside, so that reads as plausible). I also let a little red wire hang loose over the edge, because it just looks more real that way.

Note: Keep every fake wire well clear of the spinning battery holder. One stray loop in the way and the illusion literally jams.

With everything placed, I went around with an X Acto knife and trimmed off all the squeezed out hot glue. That one step made a huge difference. It took the whole thing from "hot mess" to clean and intentional.

The moment of truth. Load the hidden battery in the tray, hand it to someone, and tell them to press the button to turn on the fan. They expect the fan to spin, and instead the battery does a little pirouette while the fan sits there smugly.

1. Lower the motor in the holder so the fake battery doesn't sit up so tall. It would look sleeker and more believable.
2. Make the whole thing bigger. The fan ended up small and the spinning battery crowds everything around it. A larger footprint would give every part room to breathe and would erase the spacing problem from Step 7.
3. Measure against final parts, not bare components, so the button clearance is right the first time.

For a warm up project, this taught me a ton: basic series wiring and how much the choice of button terminal matters, soldering clean joints, designing around my printer's real tolerances, and a pile of little tricks (soldering iron hole reaming, scrap filament supports, fake solder bulbs) that I'll absolutely reuse.

What surprised me most was how much of the work was selling the illusion rather than building the circuit. The circuit took an afternoon. The fake wires, the fake fan, the silver button cap, and the spinning holder took far longer, and they're the entire reason the joke lands.

The result: it works exactly as intended. It makes people press a button expecting one thing and get another, every single time.

There are plenty of ways to take it further. You could swap in any small motor and button you've got lying around, spin something other than a battery, add a second fake button that does nothing, or shrink the whole thing into a keychain.