I have designed on a breaboard a very simple oscillator:

I used a schmitt trigger inverter(not as shown in the diagram,its just that circuit lab doesnt have a schmitt trigger inverter symbol) because with a normal inverter the output is NOT a square wave.I noticed that if the output impedance is low(such as a LED) the circuit doesnt oscillate at all but if the output impedance is high(such as a inpout pin of a arduino nano)circuit does oscillate.

For this particular circuit the duty cycle is exactly 50% with a frequency set by the RC timing constant and the transistion voltage level of the schmitt trigger.How can I make this circuit have a different duty cycle than 50%?Thanks.

 

For this particular circuit the duty cycle is exactly 50% with a frequency set by the RC timing constant and the transistion voltage level of the schmitt trigger.

It shouldn't be exactly 50%.

How can I make this circuit have a different duty cycle than 50%?

Use two resistors/pots instead of one and use diodes to steer the current.

I noticed that if the output impedance is low(such as a LED) the circuit doesnt oscillate at all but if the output impedance is high(such as a inpout pin of a arduino nano)circuit does oscillate.

Don't load the output so heavily. I'd use another Schmitt inverter to buffer the oscillator.