Parallel port trigger tells me when I’m transcoding

I decided to finish up my Cylon Eye (Larson Scanner) project by adding it as a status indicator for my computer. I record over the air programming and transcode it to DVD quality. Since things can be a bit slower when FFmpeg is running, I set it up for the Eye to scan to let me know it’s processing a video file in the background. All the details after the break but here’s the gist of the system:

  • Python script started by the FFmpeg transcoding script
  • It controls the Parallel port, driving pin 1 high to turn on the cylon eye
  • the ‘pidof’ command is called every minute for FFmpeg. When it is not found, the cylon eye is turned off and the script exits

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Light bulb microcontroller salvaged with HVSP

The ATtiny13 microcontroller from that LED light bulb is now waiting for new firmware. I used High Voltage Serial Programming to erase the chip, which clears the lock bits. I then reset the high fuse back to 0xFF. It was 0xFA before which disables the reset pin (and enables brownout detection) making In System Programming impossible.

I finished mapping out the PCB and it does use the example circuit from the buck converter's datasheet. Looks like it was outputting 12V and using a 7V zener diode to step down to the 5V source the tiny13 needed. I'm going to depopulate the PSU and patch in a 12V feed for further testing. I'm thinking my first project will be a red/green flasher for a Christmas porch light.

LED lightbulb schematic

I had a bit of time to test out the PCB from that LED light bulb. I've just been using continuity tester and ohm-meter for this. Here's the LED logic. High-side transistors but I haven't quite figured out how the resistors are wired. I've also established the A/C side of the switching regulator but I'm having trouble figuring out the output. Similar to the example in the datasheet but not quite the same.

Garage door code button

Behold, I’ve finished building a combination lock for my garage door. I’ve told a few of my friends about it and I get the “you know you can buy those, right?” responses. But no, you can’t. This is a single button code lock for a garage door. I got the idea from Alan Parekh’s project (called Button Code) and decided to build by own based around an ATtiny13 microcontroller. Join me after the break for all the details and remember, if you’re lazy you can always buy a kit that will do this from Alan. Continue reading