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Project Notes

#247 pedalShieldUno

Build and test a genuine pedalSHIELD UNO.



In the AudioDSP project, I built an Arduino pedal/DSP unit based on the Electrosmash pedalSHIELD design. It worked well enough that I wanted to build the “real thing”, not only to give myself a good baseline on expected performance, but also to payback Electrosmash in a small way. Good OSH deserves support!

Unboxing and Parts Check

Reference Qty Value Check
C2, C5, C7, C8, C9 5 6.8nF
C3, C6, C10 3 4.7µF
C1, C11 2 100nF
C4 1 270pF
R12, R13, R10, R9, R6, R4, R3 7 4.7kΩ
R5, R7, R8 3 100kΩ
R1, R2 2 1MΩ
R11 1 1.2MΩ
RV1 1 500kΩ trimmer
D1 1 LED 3mm blue
U1 1 TL972 DIP8
socket 1 DIP8 socket
SW1 1 3DPT footswitch
SW2 1 Toggle switch
SW3, SW4 2 Pushbutton
Conn1,2,3,4 1 40 pin header
J1, J2 2 1/4” Audio Jack
  1 PCB
  1 Acrylic faceplate




About 60 minutes of soldering, continuity test and inspection.

Then an electrical test, powered independantly from 5V (i.e. no in the shield). All the test points check out OK, and current draw is ~2mA. Good to go .. and it works!



The examples folder contains the collection of samples provided on the How to start programming pedalSHIELD UNO forum page. These are currently unmodified, and all work as expected.


It is surprisingly good, although it does tail off at the higher frequencies.

Quick test of the standard examples ..


This effect boosts the signal into overdrive (level determined by the pushbuttons).



A simple volume boost (level determined by the pushbuttons).



As you would expect: signal in, signal out. With a bit of high frequency noise..


Effectively downsamples the input (level determined by the pushbuttons).

Trick effect. Solo not so nice - takes too much character out of the sound.



Mixes a delayed signal with the input (delay depth determined by the pushbuttons).

Not so much delay, more like a bit of reverb?



Performs an asymmetrical clipping (top-side) to a level determined by the pushbuttons. Bluesy warm distortion..



Performs a symmetrical clipping and boost to a level determined by the pushbuttons - signals above the threshold are thrown to the upper/lower rail.

Nice fuzz, full-on distortion. It does have a harsh cut-off at lower volumes, so palm muting doesn’t work so well. Good for djenting!



Generates a metronome tone, at a frequency determined by the pushbuttons.


Performs a clean transform of the guitar signal, and logs the settings to the serial port.

Since the serial logging is performed within the interrupt routine, the signal transform is severely disrupted.


Generates a tone described in a provided dataset.


Modulates the signal volume at a speed governed by the pushbutton setting.

Great effect. The scope trace doesn’t tell the story though .. it swells the volume.





Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.