8 Pad Electronic Drum Kit

The next step on from sequencers is to build a simple electronic drum kit. The set up includes eight drum pads for a kick, snare, two toms, a floor tom, symbal and a hi-hat (open and closed). Looking around the internet I collected some ideas on building basic pads using layers of foam, aluminium (sensor) and on top a rubber pad for hitting so I assembled the pads in two rows of four with a slight arch to help with reach. The sensor I used is a common piezoelectric device placed between the foam and aluminium and wired out to the Raspberry Pi using screened cable. To connect the sensor to the Raspberry Pi I designed a simple HAT with eight comparators to provide clean input switching to the GPIO and bringing out the potentiometers used to set the trigger levels allows for the trigger sensitivity to be adjusted by the user.

My first attempt at the software for the Pi included a single kit, each sound sample could be selected on any of the eight pads. This means that you can place the drum sounds in roughly the same order as a real kit - with the exception of the kick drum (which should be on the floor) or you can mix it up a bit. As there are far more samples than just eight you are free to select any combination you want, in fact, I then went on to produce the software that lets you select between any sound from twelve drum kits on any pad. Additional features include setting pads to externally trigger a sequencer or some other device, Group A - GPIO 16 & Group B - GPIO 26, a Reset to clear all changes and Save / Load options so you don't have to remember your kit selections.

The audio out by default is via the hdmi port which can be easily changed to the A/V jack but to get the best quality sound I used the Justboom DAC HAT which is a plug and play, high resolution, digital-to-analog converter outputting a stereo line out on RCA (phono) connectors. The HAT's stack on the Raspberry Pi with the Comparator HAT placed on first then the Justboom HAT.

The zip file below contains the program, the circuit diagram, screen shots, board layout and the Gerber files for board manufacture, which if bought from JLCPCB currently only costs 1.55 for 5 plus postage. (2018/19)

RPi Drummer screen.

RPi Drummer Script and HAT details.

A short video of the Drum Machine..