#409 Conehead

The Conehead is the fourth in a series of beautiful electronic bug boards from the Boldport Club, Project #24 April 2018. This one chirps in response to light.

Here’s a quick demo..

Notes

Conocephalus is a genus of bush-crickets, known as coneheads:

Now I have one beautifully rendered in 3D by Boldport. And unlike the live video above, it chirps in response to light.

The Kit

I really appreciate the care and attention that obviously goes into selecting parts. In this kit, the speaker is particularly impressive - it even has an adhesive outer ring for securing to the PCB.

Chirp Circuit

Full details are available Boldport Conehead page, but I redrew the circuit to get a better understanding of how it works …

We basically have three oscillators comprising an RC circuit and Schmitt trigger inverter. These contribute three components to the “chirp”:

• low-frequency on/off gate
• audible frequency carrier
• modulation frequency to add “texture”

This is not pure FM synthesis, as the carrier and modulation circuits do interact. Boldport made this simulation of the circuit:

Pure Data Chirp Model

Boldport projects never fail to inspire some new learning. In the case it introduced me to Pure Data - a pretty amazing open source visual programming language for multimedia.

I reproduced the chirp.pd model and added a few more controls to make it easier to play around with. Here’s a quick example of the sounds produced with different settings:

Here are some settings that simulate the Conehead chirp:

• 428 gate frequency
• 8000 carrier frequency
• 110 modulation frequency
• 714 modulation amount

The Build

Credits and References

• Conocephalus (wikipedia) - a genus of bush-crickets, known as coneheads
• Conehead - Boldport product information
• Conehead - in the Boldport shop
• Conehead - OSH files on GitHub
• 74HC14 Datasheet
• Pure Data - used for simulating the sound synthesis
• ..as mentioned on my blog