Category Archives: Wiring Guide

Wiring of panel-mounted switches to the LCD Shield


The front panel of my Valve EchoTapper with rotary encoder (on stripboard) and four push-button switches. The Up and Down buttons could actually be left out.

The Adafruit LCD Shield kit which is used in my automation project  is supplied with pcb mounting tactile switches but they are too short to protrude through the front panel with the lcd mounted in the enclosure. Switches with extra-long actuators can be purchased to replace them but I have concerns about the long-term reliability of these little tactile switches so I opted to replace them with off-board panel mounted switches when I built my Valve EchoTapper.

A couple of builders have asked for the details of how to wire them to the LCD Shield so I’ve prepared a document to show how I’ve done it.

Click here to download the instructions as a pdf file.


How to Wire up a Rotary Encoder

I’ve personally found that adding a simple rotary encoder to the EchoTapper makes selecting and editing patches a whole lot faster and more user friendly. The Automation firmware has supported the use of such an encoder for some time but I have been remiss in not documenting how it is connected.

Before I delve into the details let me explain what the rotary control does in the EchoTapper with Automation. It basically replaces the up, down and select buttons so you can simplify your control panel to just a knob for the rotary encoder (which acts as Up, Down and, by pressing the knob, Select) and two buttons, Mem and Edit.

I recommend labelling the encoder knob Patch/Adjust and Select (Push) as in this photo.Rotary+ControlsYou’ll notice that I have retained the Up and Down buttons (and these still work but you can omit them) and turning the Patch/Adjust knob clockwise and anticlockwise will act as ‘up’ and ‘down’ respectively. Pushing the knob acts as the ‘Select’ button.

This more recent build omits the redundant Up and Down buttons:Front panel controls


Patch/Adjust Knob Functions

  • Turn to flick through presets and User patches.
  • In Basic Editor mode, turn to adjust the ‘Prog’, ‘Wet/Dry’ and ‘Feedback’ values of the patch.
  • In Manual mode, turn to change the echo model.
  • In Advanced Editor mode, turn to change the echo model then Press to select it for the patch you are editing.
  • When editing the patch name (Advanced Editor) turn to change the current letter and press to advance to the next character position.

Wiring it to your Arduino

So how do you wire it up then? I’ve covered this in detail in a document which you can download here.

The recommended parts are:

Rotary Encoder: sparkfun Part #: COM-10982
Breakout board: sparkfun Part #: BOB-11722

Automation Wiring Diagram

This pdf contains a wiring diagram to show how to interconnect the eTap2hw motherboard, Piet’s Universal Interface shield and the pots and input and output jack sockets to complete the basic wiring of an automated echoTapper unit using Piet’s original FET-based preamp design. The wiring of the valve preamp unit will be covered at a later date.

Automation Wiring Diagram (pdf)

It is assumed that you will connect the Arduino Uno, the Universal shield and the Adafruit LCD shield by stacking them one on top of the other (in that order) using ‘stackable’ headers, with the whole ‘stack’ mounted on the front panel via suitable M2.5 bolts and nuts. This earlier post shows what I mean.

The Universal Shield mounted on top of the Arduino Uno. Note the use of stackable headers to allow the LCD to be mounted on top.

The Universal Shield mounted on top of the Arduino Uno. Note the use of stackable headers to allow the LCD to be mounted on top.

It is also possible to mount the LCD separately on the front panel and connect it via four wires to the Universal shield’s I2C connector (top left in the photo above). The Uno and Universal shield would then be mounted perhaps in the base of your unit.

This would be absolutely necessary if you are mounting the unit in a 1U 19″ rack mount as the Adafruit LCD will not fit as it’s too deep. Piet should soon have available a special LCD/Buttons kit that is specifically designed to fit a 1U rack panel which will also connect via the I2C connector.

Piet's rack-mountable LCD/Buttons pcb

Piet’s rack-mountable LCD/Buttons pcb

Wiring – Stage 1

Connecting the EchoTapper Universal Interface shield (designed by Piet Verbruggen) to the Eccamatic Valve eTap2hw pcb (designed by Eric Thacker aka ‘ecca’).

The blue (Pot0), violet (Pot1) and grey (Pot 2) wires send the control voltages from the Arduino to the SKRM module (not yet mounted) on ecca’s board. The brown (+3.3V), red (SW0) , orange (SW1) and yellow (SW2) wires send the echo model select signals to the SKRM, replicating the action of the original BCD switch in the manual eTap2hw.

The rotary encoder, the push switches and the input jack socket are also wired on the front panel. The next stage is to wire up the front panel pots and the ‘peak’ LED.ImageImage