The step sensor

This started as a prototype for a step sensor that turned out well, but not quite mass production ready.

An edge lit panel sandwich placed on top of the actual Velostat pressure sensor makes for a nice "dance floor" step tile.

I'll go into details on this build in another article, for now let's focus on hooking this bare sensor to my bass guitar pedal (Darkglass Microtubes X7).

The bass guitar pedal

I don't want to go too invasive into the main board of the pedal, it just feels like a bad idea and it would quite an expensive hindsight realisation why it was a bad idea. So I'm piggybacking on the current momentary switch used to turn the pedal on and off.

But I need to somehow expose a connection, the simplest way is to butcher a slot into the housing for a connector. I'm planning to use these nice pogo connectors:

How did the slotting go? Well, rather poorly, but I got it done. Check the youtube video to see the whole journey, but here's the result:

The other side

I now need something to connect to this exposed connector. The other side of the pogo connector can use some 3D printed housing. I used TPU in part to give some strain relief at the cable flex point.

The logic

For the brains I used my favourite Wemos D1 Mini (ESP8266) that takes care of reading the sensor, triggering a relay to close the connection to the pedal and also put on a bit of a light show using Neopixel type LED strips on the edges of the pressure pad.

I've used a potentiometer for the sensor voltage divider to be able to more easily find a good value for that resistor.

Although I started with a mess of wires, I later cleaned that up with a custom PCB that also makes for a much easier mount to the enclosure. I created a project so you can easily get a few done cheaply on PCBWay's project sharing platform. It's one of those places where I like to procrastinate looking at what other people are making. 

Oh well, when it comes to the software, there's not that much to it. Simply checking the value of the sensor (the resistance of the velostat compared to the resistance of the fellow voltage divider pot/trimmer), then triggering the relay (I used a 5V octocoupled module) and doing the light show.

Speaking of the light show, I heavily modified the Pacifica example from the FastLED arduino library, and that makes for the bulk of the code. Check the code repo, there's a link in the project.