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Astable transistor component calculation Answered

Greeting All

I made a few astable and monostable circuits. The one in the attached picture gives me an output of about 1 second, but i need to know which RC components i need to make it give a mark space ratio of 6 seconds.

I'd appreciate if i can get the answer along with the calculation and an explanation of how to do the calculation.

Thanks in advance for any assistance.




The timing is set by the 10K and the capacitors. If you want an asymmetric wave form change the value of one resistor and or capacitor.

How it works.


As values are variable - especially for capacitors you may need to experiment to get exactly what you want.

Agggggg! I can no longer delete my comment to correct it Bummer.

The charge path is through the 330R I should have said. Discharge is direct through the transistor.

Thank you Rick. Much appreciated!

I understand the working of the circuit, but i cannot seem to get the formula for the RC into my head....that is why i was looking for some other examples than what the interwebs are already giving. I know that there is a calculator for doing it the 555 route and understand how that formula works too, lol, but for some reason this is tripping me up like crazy.
for instance, other than the variable that the components give +/- 20%.......
what affect does the load present etc. etc. etc.