How a POV propeller display works

In part 1 on How to make a POV display we talked about the hardware and schematic. In this part 2 we will dive in how the code works and why the POV (Persistence Of Vision) display is so cool and fun to play with.

Build a wireless energy POV display propeller clock with Android app

A POV display aka propeller display/clock is a display that uses the Persistence Of Vision (POV). By turning just a few LEDs on and off at a specific position around a circle, a full display that would normally require hundreds of LEDs can be created. This illusion of a still image is due to the eye's slow refresh rate. Without this perk we would see moving pictures instead of videos and obnoxious LED lights caused by PWM in daily life.

If you think about it is is an interesting and fun project to experiment with. This will be more obvious in part 2 where we will discuss the code and the basic principles. It can be used as a clock or display text from internet in real-time or for image display.

Here is a video with the POV display controlled by an Android app. Needless to say it looks better in person. The display can be styled by different LED colors.

How to make a double sided ultraviolet exposure box for making PCB

I had a broken Samsung MM-N6 audio system and so I've decided to build myself a double sided UV exposure box using it's front panel since it already had an LCD display, buttons and a sliding motorized panel. The sliding panel can be replaced with a door.

Here is an overview video with the version 1 of the box. This article presents an improved version of this box.

Setting preferred units in Eagle CAD to metric or imperial

If you want to set Eagle CAD to display units in either metric or imperial, there is a simple command to do this.

SET Interface.PreferredUnit n

where n can be:
0 - the default value. Eagle decides if will display metric or imperial
1 - imperial
2 - metric

To change current units in Eagle CAD, simply paste the command in the command line, replace the n with your preferred value and press enter. To confirm that it worked, open the DRC window.

Imperial units in Eagle CAD DRC window

Metric units in Eagle CAD DRC window

How to build a zener and LED diode tester using a 555 timer DIY

If you have a bunch of salvaged Zener diodes you need a quick way to sort them. In this article I describe how to build a simple test equipment that can be used to measure the breakdown voltage of a Zener diode. It can also be used to test LEDs and their color, since sometime a color LED can look white when not lit. This Zener tester is powered from a 9V battery so it doesn't involve dangerous mains voltage and can measure diodes up to 90V with the help of a 555 timer boost converter. 

I also use it for checking for burned LEDs in a mains light bulb.