Bill of materials: * The 3D printed PCB * 1x Resistor 220 ohm (1/4w), through-hole * 1x Resistor 2K2 (1/4w), through-hole * 1x NPN transitor (TO-92 package): BC635, BC637 or compatible * 1x 3mm Led through-hole * 1 x 3 pin male connector right angle Steps: * Print the PCB * Insert the components * Bend the components pin to fit in the lower channels. Trim the excess * Solder the pins between them (see the pictures) * Add a wire or something metalic for connecting the neg led pin to GND