Bodega Bay - DIY

 

PCBs are available in a four-pack for $60 including shipping in the US.
Like Solar Jerks, these benefit from being tuned intuitively and spatialized.
Email me to order: mroztronium@gmail.com

Bodega Bay is a solar-powered bird simulation circuit based on Wilf Rigter's BEAM SOUND EFFECTS circuit. A bunch of oscillators gating and modulating one another create some pretty complex and interesting sound patterns. Of all the CD40106 solar-powered chirping circuits I've worked with, this one is the most flexible (and loudest) that I've come across. Rigter's innovation of using a spare Schmitt Trigger Inverter as a piezo driver yields a pretty assertive circuit even in low light conditions.

The suggested values are a great place to start if you're after the classic bird simulator, but all of the component values can be experimented with for widely different results. Here's an example of a dozen Bodega Bays tuned differently in moderate sun.

Some notes on the choose-your-own-adventure components:

Chirp capacitors - These affect the overall pitch and timbre of the circuit. They don't have to be the same value. They'll be loudest if tuned close to the resonant frequency of the piezo you choose, but feel free to experiment

CB - The so-called "Capacitor Bucket". Similarly to how this component works in Solar Jerks, this is the circuit's reservoir in between sunny moments. Omit it for more erratic behavior and direct sensitivity to sunlight. A large value electrolytic cap (like 1000uF) will keep things fairly stable even in low light conditions.

LDR - A "light-dependent resistor" or "photocell". Gives an additional layer of variability in response to light. It's not super important which type you use. You can use a photocell for other resistors too if you like. You don't have to use a photocell at all if you don't want to... just use a regular resistor instead.

LIMIT - This optional resistor limits the range of the photocell you use. Consider what happens when you put two resistors in parallel... you get a resistance less than the smaller of the two resistors or a halved resistance if they're the same value.

You can also try using a piezo oscillator instead of a conventional piezo disc for different behaviors. These ones from Tayda work well:
https://www.taydaelectronics.com/piezo-electronic-tone-buzzer-alarm-3-28v.html



Bill of Materials
(add in some random values for the choose-your-own-adventure parts)
(1) 5-9V Solar Panel
(1) Piezo disc or Piezo oscillator (aka "Tone Buzzer Alarm")
(1) CD40106 Hex Schmitt Trigger
(4) 1N914 or 1N4148 Diodes
(2) 1K Resistors
(2) 100K Resistors
(1) 470K Resistor
(2) 1M Resistor
(1) 1uF Electrolytic Capacitor (don't sub a non-polarized version!)
(2) 10uF Electrolytic Capacitors
(1) 47uF Electrolytic Capacitor