Pet Project: Turn A Fan Into A Clock

For those of you with electronics hobbies, here is an interesting pet project that is not very difficult or expensive. In fact, you can find most of the parts lying around your house. The idea is to make an analog display clock. The finished product will have a rotating circuit board that flashes LEDs at the correct time in order to make a floating image of an analog clock.

Here is a list of basic materials that you will need:

• White box fan
• Perforated board
• PIC (or any microcontroller)
• Darlington Chip
• 2 5 V voltage divider (power microcontroller)
• LEDs with resistors
• Emitter/receiver diodes
• Toggle switch (for power)
• Battery Pack
• 12 V power supply (old phone charger)
• Clay (for inertial balancing)

Here is a list of tools that you will need:

• Solder Iron
• Solder
• High gauge wire
• Knife (cut fan up)

General Process:

1. Wire Perf Board: wire LEDs in a parallel line starting at the center of perf board and going to the edge of the darlington chip. Wire the darlington to the switched power rail and wire inputs to the PIC. Wire the power out of the battery box to the voltage divider and then through the switch. Mount the battery box in the middle of the perf board for inertial purposes. Wire the receiver diode at the end of the color LED line facing towards the fan body.
2. Remove fan blades and keep the center plastic part for mounting the perf board. Cut grooves in the hub to fit the perf board securly and use duct tape if needed to mount securely.
3. Mount the emitter onto the fan body so that the receiver passes directly in front of it. Use either a breadboard or solder parts of the voltage divider from the 12 V to the emitter. This will be your control aspect of the system.
4. As far as programming goes, I approached it so that the fan speed was relatively constant and so there were programmed delays between each LED strobe to display numbers. I treated each number as an LED number display that would flash sequentially as the fan was moving in order to show the "floating" number. Then the receiver was a callback that reset the sequence.

If everything is done right you can get something like this!

Please be careful if you try this project. Use your judgement with use of PPE and managing voltage lines.