Voltage

Low-cost microprocessor supervisors reset controllers when power-supply voltages fall below given levels. As added protection, you can also reset the microcontroller when the power supply is too high by combining a low-cost shunt-voltage regulator with a supervisor that has a manual reset input. A simple overvoltage/undervoltage-protection circuit is easy to make (Figure 1). The circuit`s output is active (low) when the monitored supply voltage, VCC, is outside a predefined range...

The op-amp rectifier in Fig 1 operates from a single supply and provides a logic output and an LED that indicate the state of the input voltage. The input-state indications are handy for calibration. Because the circuit operates from a single supply, the 2.5V reference determines the level around which the circuit rectifies input waveforms...

The op-amp rectifier in Fig 1 operates from a single supply and provides a logic output and an LED that indicate the state of the input voltage. The input-state indications are handy for calibration. Because the circuit operates from a single supply, the 2.5V reference determines the level around which the circuit rectifies input waveforms...

Sometimes, a visual indication of whether a sensed voltage is above or below its nominal value can be useful. Most approaches to overvoltage or undervoltage sensing use two voltage comparators and a resistor divider to form a window comparator. The circuit in Figure 1a is an alternative to the traditional window-comparator approach. It provides different-color indications if the sensed voltage is above or below the preset value; in this case, it is centered around 0V...

To prevent battery damage, the circuit in Figure 1 disconnects the load at a predetermined level of load voltage. This load voltage, VTRIP, is closely proportional to the battery voltage. R1 and R2 determine the level of VTRIP that corresponds to voltage of 1.15V at pin 3 of IC1. A voltage of 1.15V at pin 3 of IC1 causes the internal comparator to trip. Thus, VTRIP=1.15(R1+R2)/R1...

You can use the MC34161P universal voltage monitor to build a simple ac power-line monitor (a voltage-sensing relay). In this application (Figure 1), the mode select pin (pin 7) connects to the internal 2.55V reference (pin 1), and the IC functions as a positive-voltage window detector...