Electronics Technology Lab Report Number 9

I have completed the distortion portion of my project. By setting the values of the potentiometers in my last circuit to fixed values and putting a voltage divider with a 3.3k resistor and a photoresistor bridging the input and the output with the output of the distortion circuit, the circuit now presents a clean signal when a large amount of light hits the photocell and a distorted sound when the light into the photocell is low. The way this works is, there is a fixed resistance set on the distorted side of the signal. On the clean side, the photoresistor, when at a low resistance,  acts a a short circuit and bypasses the distorted side of the circuit. When the photoresistor is at a high resistance, it makes it more difficult for the clean signal to pass through and therefore allowing the distorted signal to pass through to the output. In order to get a very clean sound when I wanted to, I had to tune the resistances in the voltage divider so that I could get an undistorted sound and yet a full distorted signal on the other side. The 3.3k ohm resistor matched well with the resistance in the photocell and after many different trials with a range of resistances, I finally settled on that one.

I also began the construction of the tremolo portion of my project. Using a 555 timer and a 358 op-amp, the circuit uses an LED to modulate the signal from my guitar. The 555 timer lights the LED at a regular time intervals and a photocell takes in that light signal as fluctuations in resistance which changes the filter on the signal. In my incarnation of the circuit, I will use a photocell in the circuit to vary the speed of the 555 timer and therefore the speed of the tremolo.

Below is an image of my project at its current stage. On the left side of the breadboard is the tremolo section and the right side contains the distortion circuit. the large grayish-green square of circuit board are my photocells.