555 IC - 2nd Oscillator
In this project we will use a 555 timer to create a second square wave LFO. By adding a second LFO we can create much richer textures and more complex sounds.
1 x 1.5kΩ Resistor
1 x 150Ω Resistor
1 x 555 Timer
1 x 10kΩ Potentiometer
1 x 10uF Capacitor
1 x .1uF Capacitor
Please download hi res images and Fritzing files for this project HERE.
For this mod we will be using a 555 timer. These integrated circuits (IC) are very popular and can be found at most electronics shops. When reading an IC we need to look for a dot on the top of the chip. This dot marks pin 1 in the top left of the IC. Reading an IC is in a U format with pins 1-4 top to bottom on the left hand side and pins 5-8 bottom to top on the right hand side.
We will be using the 555 in its astable mode. In astable mode, the 555 puts out a continuous stream of rectangular pulses (square waves) having a specified frequency determined by our 10kΩ potentiometer. For a detailed diagram of the 555 observe the figure below. A step-by-step tutorial is listed below as well.
555 timer pinout descriptions
Place 555 in Breadboard, make sure it is placed in the center so no pins are connected.
Run a jumper from the Werkstatt ground to pin 1 on the 555. Connect an electrolytic 10uF capacitor's negative terminal (marked by a white stripe) to pin 1 leaving the positive terminal unconnected
Connect one end of a 150Ω resistor to pin 3 leaving one end unconnected
Run a jumper from the GATE OUT pin header to pin 4 on the 555. We will be using the GATE OUT to provide 5V+ to the 555, one could provide 5V+ from the internal Werkstatt power rails as well.
Place one leg of the .1 uF capacitor on pin 5 with the other leg unconnected.
Place the 10kΩ potentiometer on your bread board and connect one of the outside terminals (A or B) to pin 6. Run another jumper from pin 7 to the center terminal, or the wiper, on the potentiometer.
Bridge pin 7 and pin 8 with a 1.5kΩ resistor
Run a ground jumper to the open leg of the .1uF capacitor. Run another jumper from the positive leg of the 10uF capacitor to the terminal on the potentiometer that runs to pin 6 (A or B).
The 555 LFO is now ready to be run to an input header. Pin 3 on the 555 provides the square wave so connect a jumper from the open leg on the 150Ω resistor to whichever module you would like to modulate. In the illustration above we have run the LFO into the VCF IN to modulate the filter. The 10kΩ potentiometer allows us to increase or decrease our 555 frequency.
We can place another potentiometer as a variable resistor off the open leg of our 150Ω resistor to act as an AMOUNT control. Experiment with values between 10kΩ and 1MΩ for varying degrees of control.
2 potentiometer configuration for the 555 LFO
Experiment with simple signal filters on the output to reshape your LFO waveshape. A schematic for this final 555 LFO circuit with a single rate potentiometer is provided below.