A Fidget Spinner Electronics Project

Article By : T.K. Hareendran

Since the fidget spinner is certainly not the latest fad, somebody here might wonder what else it could be used for. Well, let me spill the beans!

A fidget spinner is a little toy built around a centered bearing and weight in three arms to help it spin fast and long. Since the fidget spinner is certainly not the latest fad, somebody here might wonder what else it could be used for. Well, let me spill the beans!

A while back, I chanced upon a cheap fidget spinner buried under the dusty pile of my old lab records. The dainty contours of the fidget spinner reminded me of the stator coil in a common brushless DC (BLDC) fan.

It was inspiring, so I started Googling and found many fidget spinner electronics projects there (surprisingly based on the same idea but with different titles). The underlying idea is nothing but accelerating the fidget spinner through the magic of electromagnetics. Since the proven idea hardly needs more brainstorming, I simply followed the same concept and built my own model of the funny fidget spinner with a couple of parts lying around. This article shows what I’ve made in hopes that you might love experimenting with your fidget spinners, too.

Now, the challenge starts! I hope you can follow the narration and transform these lines into a step-by-step guide for your reference while you’re going through the construction process.

First, I gathered a batch of small round neodymium magnets (rare earth magnets) and glued a pair of them on each of the three outer arms of the fidget spinner. During your construction, make sure that the same pole faces upward on each arm (in my case, the north pole).

This close-up clearly shows the setup.

Next, I carefully drilled a 3-mm hole in the exact center point of the fidget spinner’s hub so that the selected bolt fits nicely there — at the center bearing of the fidget spinner.

Additional nuts were used on the bolt to raise the spinner above the base (platform). You can use pine wood, plywood, or thick acrylic sheet to prepare the base of your construct.

Thereafter, a homemade electromagnet was bolted into the base, as shown in the below photo. Now, you can see a pre-wired infrared proximity detector board in the base. But you don’t have to include that one, as it’s of no use so far — just ignore that. I’ll explain about it later.

I built the electromagnet using the bobbin of a defunct, open-frame 12-V/200-Ω electromagnetic relay but replaced its old winding with new 33-SWG magnet wire. Finally, with a bobbin full of new magnet wire, it has a coil resistance close to 6 Ω. it is shown by the drawing in the below figure.

The electromagnet is one of the key parts of this project, as it makes the fidget spinner spin. This means that you’ll also have to do some guesswork to pick the perfect electromagnet with the right coil resistance. Note that if the resistance is too high, then the magnetic field will not be as powerful, but the coil will draw too much current in case of very low resistance.

Now to the trickiest part of the construction, i.e., the layout of the second key component — the reed switch. As you might have observed, the magnets on my fidget spinner are mounted so that all the magnets have their south pole facing downward. The electromagnet mounted underneath was wired in a way that the top of the electromagnet has a south pole when powered. As the neodymium magnet on one arm of the fidget spinner passes the electromagnet, the reed switch under the second arm is triggered by the neodymium magnet of that arm to fire the electromagnet. Because both the neodymium magnet and electromagnet then have the same magnetic poles, the first arm of the spinner will be pushed away from the electromagnet. When it moves far enough away, the reed switch will shut off the electromagnet. This obviously calls for a trial-and-error mechanical setup of the reed switch, under the second arm of the fidget spinner (you will need to do a little more to find the sweet spot).

This close-up clearly shows the reed switch, thanks to my USB endoscope.

Electronics circuitry is essential to drive the electromagnet. Here’s my design tailored for a minimum DC input voltage of 5 V. Note that core part is a P-channel power MOSFET — IRF9540N (T1) wires as a high-side driver. In the schematic below, one 1N4007 diode (D1) is wired across the coil (L1) of the electromagnet to prevent inductive kick from damaging the MOSFET.

Although it’s very easy to put the parts soldered together on a little flake of veroboard, I built it on a breadboard to test my build quickly. The total current demand of my entire setup was just under 110 mA at regulated 5-VDC input (~260 mA @ 12 VDC).

The P-channel MOSFET has an advantage over the N-channel MOSFET for certain applications due to the simplicity of the on/off control. The N-channel MOSFET switching +V requires an additional voltage rail for the gate — the P-channel does not. See this list of MOSFET selection rules.

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