**IC 555 Timer Calculator with formulas & Equations**

**IC 555 Timer Calculator with formulas & Equations** **IC 555 Timer Calculator with formulas & Equations** **IC 555 Timer Calculator with formulas & Equations**

Formulas and Equations for This calculator

**Frequency ( f)** = 1/ [ ln(2) x C x (R

_{1}+ 2R

_{2}) ]

**Frequency ( f)** = 1.44 / C x (R

_{1}+ 2R

_{2}) …. Where… 1/ ln(2) = 1.44

**T _{P} **= ln(2) x C x (R

_{1}x R

_{2})

**T**= 0.693 x C x (R

_{P}_{1}x R

_{2}) …. Where… ln(2) = 0.693

**T _{N}** = ln(2) x C x R

_{2})

**T**= 0.693 x R

_{N}_{2}x C …. Where… ln(2) = 0.693

Where;

**C **= Value of Capacitor in Farads

**R _{1} and 2R_{2}**= Value of the Input Resistance

**= Frequency in kHZ**

*f***T**= Positive or High Time from each pulse

_{P}**T**= Negative or Low Time from each pulse

_{N}**Enter values and click on calculate. Result will display the calculated quantities. **

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Frankly I think that’s abetulosly good stuff.

I am confused about the value for Tn , that this time required for negative cycle , i think that should be 0.676 *( R1+R2) .

Can you please share the derivation for it .

Kartik, the Tn equation is correct. According to the datasheet for the 555 Timer, astable output, the following formulas are used (this is how the calculator works). Tp = .693 * (Ra + Rb) * C and the Tn = .693 * Rb * C.