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README.md
chirp.pd
conehead.fzz

README.md

#409 conehead

The Conehead is the fourth in a series of beautiful electronic bug boards from the Boldport Club, Project #24 April 2018.

Here's a quick demo..

clip

Build

▶️ return to the LEAP Catalog

Notes

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

clip

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

The Kit

conehead_kit

Qty Item
1x 1W 8Ω 13mm speaker, Multicomp MCKP1330SP1-4723
1x Phototransistor, Everlight PT333-3C
1x Hex Schmitt trigger inverter, ON Semi MC74HC14ADR2G
1x 47µF electrolytic capacitor, Multicomp MCUMR6V3476M4X5
1x 1µF ceramic capacitor, Suntan TS170R1H105MSBFA0R
2 0.1µF ceramic capacitor, Multicomp MC0805B104K500A2.54MM
1x 0.01µF ceramic capacitor, Suntan TS170R2A103KSBBA0R
12 x 4.7KΩ resistor, Multicomp MCF 0.25W 4K7
1x 220Ω resistor, Multicomp MCRE000029
1x 2032 battery holder, Linx BAT-HLD-001
1x Small signal diode, Diotech 1N4148
1x SPST switch, Apem IKD0103101
16cm 20AWG wire

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.

conehead_kit_parts

Chirp Circuit

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

Schematic

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:

falstad_simulation

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:

clip

Here are some settings that simulate the Conehead chirp:

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

pd_chirp_model

The Build

conehead_build_left

conehead_build_right

conehead_build_detail

Build

Credits and References