ElectroCalc is a fast calculator for electro-electronic projects. The PRO version of ElectroCalc doesn't have any ads and it's always growing! V1. 0. 9 Available calculations: Timer 555 - Monostable. Timer 555 - Astable. Ohm's Law. Resistor - Color Code. Zener Diode - Voltage Source. LM317 - Voltage Source. LM317 - Current Source. Equivalent Resistance. Voltage Divider.