Is there correction point of attached circuit, please let me know.
【Ploblem】
・Customer made attached circuit and external value.
・They hope that clock output is "Duty:40%, 4kHz", but result was "Duty:70%～, 6kHz".
・Is Ra:Open mistake? or is circuit have the other problem?
Best regards,
Satoshi
Satoshi,
The first problem is that Ra can't be zero otherwise the discharge pin will try to short out the 12V supply which would be very stressful for the 555 timer.
As drawn, the duty cycle will be greater than 50% because the charge resistance RA + RB is greater than the discharge resistance RB.
A steering diode can make charge resistance less than discharge resistance.
