Halloween Eyes - Trimble

Over the years I’ve worked on various designs of my “eyes” to put out in the bushes on Halloween night. I started with a microcontroller and lots of wired pairs of 3mm LED’s inserted into plastic carriers, and eventually worked up to a board design that not only acted as the carrier, but also used 10mm LED’s to make them more easily visible.

My first cut at this design was based on a simple 555 timer circuit (mostly because I discovered we’d inherited a reel of SMD 555’s, so…why not). This design is great for the novice, since there’s no programming required…and no programming means no special software and no special programmer. Downside is less control, but it works well for the basic “two eyes blinking” that I was going for.

Multiple power options were included, since I wasn’t sure if I wanted to use USB or a 9V Battery. If you want to use a battery, the USB connector and parts don’t need to be installed. And if you prefer USB, you don’t need the regulator and associated parts. The units are designed to be chained in series with the first set of eyes providing power to the rest, so any additional boards don’t require either power components.

The following describes the board in better detail.
Halloween Eyes Assembly Doc

Board Files (Gerbers, Schematic and Layout):
Halloween Eyes Gerbers
Halloween Eyes Schematic

Limitations / Modifications:
– Power: This design is “always on”. A FET/photoresistor circuit was added with limited success due to the unexpected brightness of a neighbor’s porchlights (details to come)
– LED Brightness: The 10mm LED’s were purchased from eBay and no specifications were provided. The 470Ohm current limiters were a ballpark guess and had to be changed to 1kOhm to keep the “eyes” from blinding passing children.
– Eye Blink: To make certain eyes blink differently, it was necessary to replace the 200kOhm pots with 100kOhm.

Future Additions:
– Sensor Lines: This will allow for the addition of sound and motion devices when a line is tripped (laser, IR, etc.).
– Photosensor: A better, adjustable photosensor to compensate for light-polluting neighbors.
– Control Lines: To allow for the eyes to “wink” instead of just blink. Not sure if this would be worth anything, but just a thought.