Sens is a eurorack module allowing you to control your synth through a wide variety of sensors.
What is Sens?
Sens is a plug-and-play eurorack module interfacing a wide variety of passive sensors with your synth.
Sens provides 2 channels, allowing you to connect up to 2 sensors to your synth.
Get away from the knobs
Connect with your sound
Make a more visual performance
How do I use Sens?
- Choose the sensor you need, and connect it to the module through a stereo audio cable.
- Connect Sens to the parameter you want to control.
- Hold the calibrate button while showing the maximum and minimum values you will use. When you release the button, the module will save the range of values that you will use.
You’re all set! You can now touch your sound!
What sensors can I use with Sens?
You can use any passive sensor, analog (pressure, light, …), or logical (buttons, tilts…).
For demo purposes, the module comes with 3 plug-and-play sensors.
A pressure sensor, outputting more voltage the more you press it
A light sensor, outputting more voltage the more light it gets
A tilt sensor, which sends triggers when shaken
How to build my own sens?
In this last part, I will explain how you can build your own sens module.
- The wiring
- The code
- The module itself
- 3 sensor blocks
1] The wiring
Every part you will need
To make 1 sens module and the first 3 sensor blocks, you will need :
- 1 Arduino Nano
- 2 DACs (MCP4725)
- 2 buttons
- 1 Voltage regulator (LM2586)
- 1 pressure sensor
- 1 light sensor
- 1 torsion sensor
- 5 10kΩ resistors
- 1 piece of stripboard
- 5 Stereo 3.5mm audio jack female sockets
- 2 Mono 3.5mm audio jack female sockets
- Stereo 3.5 jack cables
- cables, solder, a soldering iron…
The module is based on an Arduino Nano. For each channel, the Arduino is plugged to:
- 1 sensor through a stereo audio cable
- 1 button to calibrate the values
- 1 Digital to Analog Converter to output CV
The sensor through a stereo audio cable
This is how you would usually plug any analog sensor to an Arduino:
In the case of Sens, we don’t want to have the sensors stuck in our case. The electrical signal of the sensor goes through a stereo audio cable (because we need 3 pins) directly to the Arduino. The sensor and the resistance are located in the sensor block.
This is how you plug an analog sensor to an Arduino through a stereo audio cable:
The first stereo jack is plugged to the Analog 1 pin and the second is plugged to the Analog 2 pin of the Arduino Nano.
Even if I experimented with the kind of stereo audio jacks on the scheme, I swapped them with audio jacks with a screw for the final product. You can find the exact one I used on GoTronic .
The Button to calibrate the values
The button is used to calibrate the module to the sensor that you plugged in. It’s just a simple momentary button, here is how to plug it.
The first channel’s button uses the digital pin 2 and the second one uses the digital pin 3.
The DAC to output CV
To output Control Voltage, we use a Digital to Analog Converter (DAC). The Output signal of the DAC goes directly to the mono audio jack to control synth parameters.
I used the MCP4725 DAC made by SparkFun. (There also is an Adafruit version of this DAC but you may have to plug it a little bit differently.) The DAC uses the I2C bus of the Arduino. It allows us to plug 2 DACs on the same pins and to access each of them by a specific address in the code. In the case of the SparkFun version of the MCP4725, you can choose between 2 different addresses for your DAC just by changing the small solder point on the component. For more information on how the SparkFun MCP4725 works, you can go to this article on “Henry’s bench” blog.
If you want to have a real module at the end, you will have to supply power to the Arduino. Since the voltage in synth cases is up to 12v and the Arduino Nano works best with 7v we need to lower its voltage. There are a million ways to do it but I choose the simplest one. I just added a voltage regulator which is called LM2586.
Here is how to plug the tension regulator to the Arduino Nano. Don’t forget to adjust the tension regulator to 7v before plugin the Arduino.
Don’t forget that you will have to connect 2 stereo jacks, 2 buttons, and 2 DAC with mono jacks to be able to plug 2 sensors and to output 2 Control Voltages.
Now that we have everything connected, we should have something like this :
2] The Code
The code is pretty simple. It’s just a map() of the values of the sensor.
The module outputs voltages through the DAC depending on the value received from the sensor. A simple button allows you to calibrate the input.
The code is commented on in the file itself so I will not explain it here. You can download the Arduino code here:
3] The module
If you want the full package, you can make the actual module. We may not have the same tools but I will show you how I did mine.
I decided to make mine in a see-through plastic plate because I find it cool but here is the design I originally made for the panel of the module. You can print it on a sticker that you stick on to the face of the module.
My version of the module is 4hp because of the size of the power supply but you may be able to go thinner. I used a strip bender to bend the plate so the whole module is only in 1 plate.
Here is the illustrator file of the laser cut if you want to do yours exactly like mine.
Now you have got everything to make the module. We will now look at the sensors blocks
4] The sensors blocks
The module is in fact only one part of Sens. The interface wouldn’t work without the sensors that are housed in the sensors blocks. The sensor blocks are designed to be easy to handle and use.
I made 3 3D printed sensor blocks: a pressure sensor, and a light sensor, and a tilt sensor.
You can download the 3D models here (unfortunately I can’t seem to find the pressure sensor housing but I’m sure you’ll figure it out 😉 )