555 I.C. Freq. generator

SgtWookie

Joined Jul 17, 2007
22,230
Actually, from the conventional astable multivibrator configuration of R1 from Vcc to pin 7, R2 from pin 7 to pins 2&6, and C1 from pins 2&6 to GND, R2 can be replaced with a pot, and a single diode can be used (preferably a Schottky with a low Vf), anode to the wiper, cathode to pin 7, so that the timing cap C1's charge/discharge paths are dependent on the wiper position, thus allowing a wide PWM duty cycle adjustment.

You won't get to 0% or 100% duty cycle, but a range of ~3% to ~97% is do-able.
 

Thread Starter

RRITESH KAKKAR

Joined Jun 29, 2010
2,829
The duty cycle is the ratio of the two resistors since both resistors charge the timing capacitor and only one of the resistors discharges the capacitor.
It cannot reach 50:50 or more unless two diodes are added then a pot can make any duty cycle you want.
Sir where it is used and why diode are used??
 

Thread Starter

RRITESH KAKKAR

Joined Jun 29, 2010
2,829
Hi, this is my ckt. i want to know how to connect active gate output common as one method is to place diode at each gate output, but it will be very difficult and costl.
Pls. suggest me how to overcome this..!!

Thank's..!!:D
 

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