555 VCO

Been playing around with 555 timers again. This time, I made a Voltage Controlled Oscillator. It’s really cool. By applying a voltage to pin 5 on the 555, I can adjust the frequency of the output wave. I’m testing it with my Velleman O-scope and have graphed some data with the google chart machine. The timing of the center frequency is set by resistors and a capacitor hanging off of pins 7, 6, and 2. I’m using 10K between +V and pin 7; a 470ohm between 7 and 6; and 6 is connected to 2 and also has a 0.2uF capacitor to GND. The 555 I’m using is made by ST Microelectronics. Very happy to say that the output is stable and predictable over a wide range of voltages.

Here’s a chart of the frequency at V/2 over a range of power levels.

Tracking current consumption here.

Testing Polyphonic signals now.
I feel the slight distortion at 4.75V in first graph may be due to temperature.
These curves will be compared with curves from the 2nd prototype.

Here, again, I will test different temps

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