555 Timer Frequency and Duty Cycle Calculator

Posted on Feb 5, 2014

Enter values for R1, R2, and C and press the calculate button to solve for positive time interval (T1) and negative time interval (T2). For example, a 10K resistor (R1) and 100K (R2) and 0. 1 uF capacitor will produce output time intervals of 7. 62 mS positive (T1) and 6. 93 mS negative (T2). The frequency will be about 70 Hz. R1 should be greater th

555 Timer Frequency and Duty Cycle Calculator
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an 1K and C should be greater than. 0005 uF. Scroll down page for basic 555 information (pinout and two basic circuits). Pin 1 (Ground) - The ground (or common) pin is the most-negative supply potential of the device, which is normally connected to circuit common when operated from positive supply voltages. Pin 2 (Trigger) - This pin is the input which causes the output to go high and beginthe timing cycle. Triggering occurs when the trigger input movesfrom a voltage above 2/3 of the supply voltage to a voltage below1/3 of the supply. For example using a 12 volt supply, the triggerinput voltage must start from above 8 volts and move down to avoltage below 4 volts to begin the timing cycle. The action islevel sensitive and the trigger voltage may move very slowly. Toavoid retriggering, the trigger voltage must return to a voltageabove 1/3 of the supply before the end of the timing cycle in themonostable mode. Trigger input current is about 0. 5 microamps. Pin 3 (Output) - The output pin of the 555 moves to a high level of 1. 7 volts less than the supply voltage when the timing cycle begins. The output returns to a low level near 0 at the end of the cycle. Maximum current from the output at either low or high levels is approximately 200 mA. Pin 4 (Reset): - A low logic level on this pin resets the timer and returns the output to a low state. It is normally connected to the + supply line if not used. Pin 5 (Control) - This pin...

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