I'm trying to build a low frequency oscillator (think about 0.01Hz - 5Hz) using a TL072 as an astable multivibrator. Here's the circuit in LTspice:
And here's the simulated output:
Where does the 2.8s initial delay come from? It appeared once I raised R to 1M to decrease the frequency to suit my range. Also, where would one put a potentiometer for frequency adjustment? I also suspected using an electrolytic capacitor in this configuration would damage it as it's repetitively getting a negative voltage, so I limited C1 to 100n.