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..
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.
|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|
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.
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