Hi,
Can someone explain why varying the Vcc for a 555 timer chip, say from 6 volts up to 15 volts, cause a change in the pulse frequency (measured on the output pin) when the 555 is configured as in the astable mode? None of the documentation I've read on calculating the frequency ever seems to talk about the voltage, however, from experimentation, I can clearly see a big change in the output frequency from below 20KHz to up around 30KHz as the voltage increases. The basic configuration of the circuit used
r1=680R
r2=62K
c=330 pF
I have read that both R1 and R2 should be > 1K, so maybe my r1 (680R) might be what is causing this odd behaviour.
Can anyone shed some light on why this frequency change is occurring?
Can someone explain why varying the Vcc for a 555 timer chip, say from 6 volts up to 15 volts, cause a change in the pulse frequency (measured on the output pin) when the 555 is configured as in the astable mode? None of the documentation I've read on calculating the frequency ever seems to talk about the voltage, however, from experimentation, I can clearly see a big change in the output frequency from below 20KHz to up around 30KHz as the voltage increases. The basic configuration of the circuit used
r1=680R
r2=62K
c=330 pF
I have read that both R1 and R2 should be > 1K, so maybe my r1 (680R) might be what is causing this odd behaviour.
Can anyone shed some light on why this frequency change is occurring?