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Last Updated
03/31/2019
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Detailed entries for one subject from the INDEX TO HOW TO DO IT INFORMATION. |
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VOLTAGE MONITOR sa BATTERY MONITOR sa ELECTRIC POWER CONTROLLER sa ELECTRIC POWER-CONSUMPTION MONITOR sa ELECTRIC POWER-FAILURE ALARM sa VOLTAGE PROBE x COMPARATOR (VOLTAGE) x MONITOR (VOLTAGE) x VOLTAGE COMPARATOR xx ELECTRIC xx ELECTRIC POWER SUPPLY xx ELECTRIC POWER-FAILURE ALARM xx ELECTRONIC TESTING xx VOLTMETER & MULTIMETER Power supply voltage monitor uses a tricolor LED display to indicate whether the voltage is above, below or within acceptable limits. Can monitor voltages between 5 and 15V. An AC power-line monitor displays the voltage on a 3.5-digit LED. Build an RS-232C breakout box, a decade voltage-level indicator, and a terminal simulator. These diagnostic tools will help you make working serial connections. A multiple test-point monitor measures voltage at a number of circuit points simultaneously. How to add a "fuel gauge" to your Radio Shack Model 100 lap computer to give you a visual indication of the state of the batteries in use. The "fuel gauge" is basically a voltmeter with a conversion program that correlates the battery voltage to the ampere-hour capacity of the batteries. AC powerline monitor displays either the voltage level or relative noise level on the LED display. Est. cost: $45. Voltage tester glows red when connected to 5- to 400-volts, either AC or DC. Also shows polarity of DC voltage. Circuit will indicate when a voltage level either falls below or rises above a particular value. Can be set to trigger on whatever voltage you want. Voltage comparator circuit turns on an LED whenever an input voltage falls below a reference voltage. Uses the LM339 IC. Over/under voltage protector monitors AC line voltage and disconnects the load if the input voltage goes below 95 volts or above 130 volts. Brief power outages (1/10 second) won't disrupt service. Est. cost: $40 (kit). Circuit used to detect an increase in voltage. A relay pulls in whenever the voltage exceeds about 17 volts DC. AC line voltage monitor causes a lamp to blink, until reset, should line voltage drop below 100 volts. Voltage tracker can monitor a voltage unattended, remember the direction of voltage fluctuation, or the arrival or non-arrival of a pulse. Est. cost: $25. Power supply balance indicator. Three LED's indicate when the positive and negative levels of a split power supply are within 1% of each other. Circuit turns on an LED whenever a battery voltage drops below a predetermined level. Automobile battery voltage monitor circuit lights an LED if voltage falls below 11 volts. Battery monitor circuit lets you know when battery voltage falls below the preset limit. AC-line disturbance monitor detects noise and high/low voltages. Build a 12-volt battery-voltage monitor to determine battery status under normal equipment load. Using op-amp comparator circuit chips to detect and measure real-world conditions. Circuits for monitoring temperature, light level, voltage, etc. Build the low-battery alarm. Simple circuit monitors the voltage of back-up batteries in clocks, timers, etc. Sounds an alarm when voltage drops to 5 volts. Circuit for an inexpensive dc supply voltage monitor that sounds an audible warning if voltage drops below a preset level. Circuit which can be used to monitor voltage output of a variable voltage power supply. An LED will light up at preset voltages (such as 5 and 12 volts) when your output reaches that level. Experimenting with the analog comparator, a special circuit incorporating the operational amplifier. Circuits include (1) an adjustable light-dark detector, (2) adjustable-threshold temperature-controlled relay, (3) a sine- to square-wave converter, and (4) a peak-voltage detector. Using voltage comparators. A hands-on look at the popular and readily available LM339 which features four separate comparators in a single 14-pin DIP. Used in circuits to convert from analog-to-digital, monitor voltage levels, convert from one logic family to another, etc. R/C aircraft crash saver. An accurate battery status indicator for on-board radio-control gear ensures availability of sufficient power for takeoff and landing of costly model airplanes. Uses LEDs to show if Ni-Cd battery has 4.8-, 4.6-, 4.4-, or 4.2-volts available. Visual regulator monitor. Separate circuits with LEDs alert you to loss of regulation, overcurrent and thermal problems caused by regulator ICs in power supplies. Automotive battery/charging system analyzer. Simple, low-cost circuit uses a series of LEDs to report on vehicle electrical-system status. AC line monitor alerts you when ac line voltage and frequency conditions are detrimental to the health of your computer and other sensitive electrical equipment. Battery monitor. An easy to read voltmeter uses green, yellow and red LEDs to indicate the state of charge of a 12-volt battery. Est. cost: $26. Voltage monitor for a 12-volt supply will turn on a lamp if the voltage drops below a certain level. Est. cost: $6. Electronic circuit switches off a 12-volt battery if its output drops below 9 volts. Circuit for a 115- to 125-volt power line monitor. Circuit with zener-controlled relay trips alarm if the voltages exceed the zener point. A look at the voltage comparator and its use in logic control and instrumentation equipment. Application circuits for a reference supply, a 100-kHz multivibrator and oscillator, and a voltage controlled oscillator. Circuit for a wide range voltage probe. Can indicate the presence of any voltage from 1.5 to 150 volts ac or dc. Circuit for a 117-volt ac line monitor. Uses for the multiple integrated circuit LM339, a quad comparator. Containing four independent voltage comparators, it is used in circuits for (1) a voltage-controlled oscillator, (2) limit comparator and (3) limit comparator operated as a programmable light meter. DC low-voltage monitoring circuit turns on an LED if voltage drops below a preset level. The analog comparator. A circuit which compares an input voltage to a reference voltage and changes the state of its output only when the input exceeds the reference voltage. Several applications reviewed. The digital comparator (magnitude comparator). Digital counterpart of the analog comparator discussed in the May 1979 issue. Low voltage indicator circuit for batteries. Est. cost: $2. CMOS guardian will indicate if any 117-volt ac line-operated device has been switched on. Use it to detect unauthorized use of electrical devices. Does not sound an alarm or flash any lights. An early-warning car battery-drain indicator replaces the standard "idiot" light with a visual-audible monitor which indicates low, normal and high voltage conditions. Est. Cost: $28. Battery monitor circuit contains four LED's that are set to switch on if the supply voltage falls below any of the preset thresholds. Simple metering circuit for monitoring voltages that don't vary too much (such as a car battery). Digital electronics course. A close look at comparisons. Fundamental course in design and operation of comparators (a special op-amp used to compare the voltage levels presented to its two inputs). Digital electronics course. Binary comparitors. How error and parity checking and other computer functions are implemented. LED indicator circuits for all occasions. (1) AC pilot light. (2) DC pilot light. (3) Polarity indicator. (4) 5-volt voltage-level indicator. (5) Oscillator-driven flasher. (6) Decoder converts audio CW code into visual dots and dashes. Voltage-level indicator circuit will indicate three different pre-set input voltage levels. Adjustable voltage monitor can be used to check whether the voltage in a circuit remains within a given range. Voltage monitor and detector circuits. (1) Glitch detector monitors a DC-voltage for a change (glitch) which can cause problems in a computer. (2) AC noise detector. (3) AC power-failure monitor checks for voltage glitches or failures. Op-amp applications. (1) CMOS-interface driver, (2) dual-voltage supply, (3) AC amplifier, (4) adjustable comparator, (5) dual-voltage comparator, (6) four-level voltage detector, and (7) voltage window. Build an AC line-voltage monitor that uses LEDs to indicate the voltage level in seven steps from 100 to 132 volts. Est. cost: $11 (kit). Simple op-amp application circuits. (1) Fixed voltage reference. (2) Light-operated sensor. (3) Alarm sensor. (4) Voltage-level sensor. (5) Peak-voltage detector and hold. (6) DC motor driver and reverser. (7) Simple timer circuit to delay relay operation for up to 30 seconds. AC power-line voltage monitor is designed to detect power outages, sags, surges, spikes, and large harmonic distortion. Est. cost: $50. Voltage-monitoring circuits and some typical applications. (1) Simple low-voltage. (2) Simple over-voltage. (3) Dual voltage. (4) Dual voltage with alarm. (5) Dual voltage with relay disconnect. (6) Over-voltage with discrete components. (7) Low-voltage with discrete components. (8) Over-voltage cutout. (9) Over-voltage with latching relay. (10) Over-voltage using fuse protection. Household voltage monitor turns on an alarm if current falls below a safe level for motor-driven home appliances. Brownout alarm sounds a shrill whistle if your household electrical power dips below a safe level. Build an inexpensive expanded-scale voltmeter to monitor ac line voltage. Low-voltage alarm circuit is designed to work with battery powered devices. Draws little current and does not interfere with other devices powered by the battery. LED bar-graph display. Eight simple electronic gadgets, including a line voltage monitor. Simple circuit uses any common op-amp to form an analog comparator with variable hysteresis between two trip-points (one fixed and one movable). Low-battery indicator uses an LED to signal when the battery voltage has dropped below a pre-selected level. Low-battery warning. A circuit which constantly monitors the condition of batteries and signals if their voltage falls below a preset value. Sensing circuits. Three methods for sensing when a circuit is active. Looks at light, coil, and series dropping resistor sensing techniques. Power supply over/under voltage monitor is built around the Motorola MC3425/MC3525 monolithic power supply supervisory circuit. A handy low-voltage indicator. Low-power circuit turns on an LED, buzzer, etc. whenever the base voltage drops too low. Working with voltage comparators. Voltage-comparators and window-comparators are extremely versatile circuits. Here are some practical circuits that you can put to use. Over-voltage indicator circuit will light an LED, sound an alarm, etc. when a particular voltage level is reached. An under-voltage monitor circuit sounds an alarm if voltage drops below 6.7 volts. Automobile battery monitor circuit has three LEDs to indicate four voltage levels (11, 12, 13, and 14 volts). Explanation of a "crowbar" circuit which monitors the output voltage of a regulated power supply. Powerline monitor shows the AC line voltage and the relative noise level on the line. Can also be used to test line filters quickly and easily. Est. cost: $45. Glitches in the power line. A look at their causes and monitoring equipment. Voltage-detection circuit will light an LED whenever a variable power supply is putting out a particular voltage (5-, 10-, 15-volts). | |||||||||
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