Spur-of-the-Moment Prototype Hack

A project log for CPOV - a Crappy Persistence of Vision display

Quick and dirty spinning POV project

mike-szczysMike Szczys 05/12/2014 at 20:120 Comments

Like I said before, I've been wanting to do a grand POV display build for a long time--at least four or five years. On Saturday morning I realized I had a couple of hours free and I just started hacking together the parts I had on hand. I plan to improve each part of this design over time and incrementally build something awesome.

I started with this old cassette deck assembly. I didn't get a picture before removing the motor but it was screwed to the two black pillars to the left of the metal bracket.

This metal wheel attaches to the plastic gears driven by the motor. The trio of holes is perfect for tapping 4-40 threads

After tapping the holes I added stand-offs and cut the excess off using a Dremel and cutoff wheel

This piece of substrate is a circuit I over-etched. I'm using it as the base of the spinning display

One of my very first microcontroller projects (almost 10 years ago now) was an attiny2313 Larson scanner. I found that board in the bin and screwed it to the substrate.

The white CR2032 battery holder was salvaged from an old motherboard. I also added a 6-32 bolt and several nuts as a crude way to balance the board.

Here's a side-view of the working display. I drive it with an old atx psu (the motor is 12V). At this point the thing works. I googled for "attiny2313 pov" and found that Adafruit has firmware that works for this setup. I connected 8 LEDs to PORTB because that's the only full 8-bit I/O on the chip. Adafruit's firmware is designed for the same arrangement.

It took me two hours to get to this point and everything works except that I need to add a positional sensor to the display. I have some IR transmitter/detector pairs which will work but didn't have time to add them yet. Once I add these I'll write my own firmware that is extensible. I plan to add communications to this later on so that I can push data from a remote device.

The next day I spent about 30 minutes building a base for the display. Above is a piece of 1/4" plywood. I'm about to cut a dado in it so that i can mount the motor (It's too think otherwise).

Cleaning up the dado with a chisel

Assembly mounted on the plywood

Added wood on either side of the plywood and screwed that to a hunk of 2x4. This has to be clamped to my bench as the spinning part is still rather off-balance.

Here's a quick video of the thing. You can see that it doesn't have a positional sensor. I turn the PSU on and off to get the speed just right. It says "minipov!" if you look closely.