Generate pwm using ic 555: Add a diode

Method 2; Longer low time: Add a Diode

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  The schematics.

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  The simulations.

The added diode $D$ shorts the out the resistor $R_{2}$ during the charging cycle; thus the capacitor charges directly from Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle R_1} removing Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle R_2} , though a small leakage current will flow through it. The constants are modified due to the voltage drop of Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle D} .

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \begin{align} T_\text{on} &= 0.8 R_1 C \\ T_\text{off} &= 0.7 R_2 C \\ f &= \frac{1.44}{(R_1 + 2R_2)C} \end{align} }

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle pwm% = \frac{ T_\text{on} }{ T_\text{on} + T_\text{off}} = \frac{0.8 R_1 C}{0.8 R_1 C + 0.7 R_2 C } = \frac{0.8 R_1 }{0.8 R_1 + 0.7 R_2 } }

The simulation file: File:555 diode 300 300.circuitjs.txt