Fun with Hex Schmitt Triggers

Recently I've been playing around with some of the oscillator projects outlined in Nicolas Collins' excellent "Handmade Electronic Music", a must-read for anyone interested in home-grown audio. This finished project is constructed around a single Hex Schmitt Trigger integrated circuit that is wired to oscillate at three different rates, resulting in a nice droning cacophony. Two of the oscillators are controlled by photoresistors, and the third is regulated by a 50k potentiometer. A second 10k potentiometer is wired to the positive line from the battery (creating a variable power starve), and also to the output line of one of the photoresistors - dunno why, but it seems to add that extra little something something.

Here's what the final breadboarded circuit looks like:


Sounds good - now it's just a matter of transferring it from the breadboard to a regular circuit board, and finding a box to house it.

Interior of completed Drone Box. The battery is held in place with velcro.

The two small holes at the center are for the photoresistors, which are held in place by plastic soda straws.

Then I put together a second Hex Schmitt Trigger oscillator, the output of which is connected to a single LED. The LED blinks at a variable rate controlled by two potentiometers.

Next I inserted an LED into one of the photoresistor holes in the Drone Box. The LED was then attached to the second oscillator output with clip leads and held in place with electrical tape.




So, what does it sound like? The first video below shows the Drone Box with the pitch of the photoresistors manipulated by a flashlight. The second video shows the box with the oscillation regulated by the blinking LED.