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Fidget Spinner

The fidget spinner circuit causes the LEDs to switch on and off rapidly. How fast, well too fast to see while the spinner is still, but if you spin it then you'll see the pattern as the lights switch on and off.

The circuit is constructed on a small printed circuit board that fits inside a clear plastic case. In the centre is a ball bearing and two plastic cups that fit into the bearing. The circuit is layed out in such a way to be balanced when it rotates about the central axis.

Fidget Spinner

Circuit Diagram

Technically this is called an astable multivibrator. The fidget spinner circuit alternates between two states. Each state corresponds to one pair of LEDs being switched on and the other off. There's a really good simulator showing this type of circuit at falstad.com that shows the way the current and voltage changes.

Fidget Spinner circuit

Assembling the kit

These are photos showing the Fidget Spinner circuit board being assembled and in operation.

The circuit board is silk screened with the outline and value of each component.

The components are:

Item Function / Description
Transistor 9013 x 3, 8550
Resistor 1k x 5, 10k x 3, 1M x 3
Capacitor 0.1uF x 3
LED Blue, green, orange, red
Battery CR927 x 2
Switch press button

When assembling the circuit take note of the space between the circuit board and the case. The LEDs need to be fitted flush to the circuit board, and the capacitors and transistors need to be bent over flat onto the board before soldering into place. A 1mm dot of blue tac can be used to hold the switch while it's soldered in place.

It doesn't matter too much which position each coloured LED goes in. The longer lead on the LED goes in the hole marked with a +

The original kit was obtained from AliExpress.