Voltage Detectors / Sensors / Monitors Electronic Circuits

Voltage Detectors / Sensors / Monitors
#'s - B C - D E - M N - V
Sensors / Detectors -- Main Page
Last Updated on: Sunday, May 19, 2013 04:49 AM

Circuits Designed by Dave Johnson, P.E. :

9v Battery Voltage Monitor
This circuit turns on a LED whenever the voltage of a standard 9v battery connected to the circuit drops below 7.2 volts. It uses a LTC1440 comparator, which also contains a 1.18v reference diode. In standby mode, the circuit draws only 4uA. (added 7/06)

Acceptable Voltage Indicator
I have used this circuit many times in custom test fixtures where a simple go-no go indication was needed. The circuit can also be used to adjust a particular voltage be within specific high or low limits. The three LEDs will indicate if the voltage is high, low or OK. When connected to other converters, such as a frequency to voltage converter, a current to voltage converter or a power to voltage meter, it could provide a quick indication of a proper level.

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

“Hippasian” nonlinear VFC stretches dynamic range - 19-Feb-09 Issue of EDN A voltage-to-frequency converter uses square roots to extend dynamic range by orders of magnitude.... [Design Idea by W Stephen Woodward, Chapel Hill, NC]

3 Digits Digital Volt Meter with PIC16F676 - This is simple 3-digits digital volt meter.PIC16F676 used to read analog signal(voltage) and display the value on 3-digits 7-segment. You can apply similar principles to measure DC current with parallel R shunt. …....

3 Level Audio Power Indicator - Battery-operated3 LED display that connect it to loudspeaker output (added 04/02)

3-Digit DVM Voltmeter - Uses 3161, CA3162 ICs ….(design added 11/08)

3-Digit Volt/ Amper Meter - Even if the digital multimeters have dominated in a lot of applications, in the measurement, exist the need for existence of instruments of clue in various appliances, voltage and current, …....

9v Battery Voltage Monitor - This circuit turns on a LED whenever the voltage of a standard 9v battery connected to the circuit drops below 7.2 volts. It uses a LTC1440 comparator, which also contains a 1.18v reference diode. In standby mode, the circuit draws only 4uA.... [Hobby Corner Circuit by Dave Johnson]

AC Line Under/Over Voltage Alarm - Power lines, which deviate much beyond normal voltages can damage expensive electronic equipment. The circuit below sounds an alarm whenever the line voltage is higher or lower than normal. I set the alarm limits at about +-15% from standard levels. The circuit rectifies and filters the power line signal. I set the resistor values, so the DC voltage produced is close to 1% of the RMS value of the line. Thus, a 120vac line would yield about 1.2v DC. That voltage is fed to a pair of voltage comparators. The outputs of the comparators decide if the sampled voltage is above, below or acceptable.... [Designed by David A. Johnson]

AC Voltmeters & ammeters - Electronic Circuit design (added 02/05)

Acceptable Voltage Indictor - I have used this circuit many times in custom test fixtures where a simple go-no go indication was needed. The circuit can also be used to adjust a particular voltage be within specific high or low limits. The three LEDs will indicate if the voltage is high, low or OK. When connected to other converters, such as a frequency to voltage converter, a current to voltage converter or a power to voltage meter, it could provide a quick indication of a proper level. …. [Designed by David A. Johnson]

AN557: Four Channel Digital Voltmeter with Display & Keyboard - Microchip Application Note Published 27-May-05 (app note added 2/06)

AN779: Using the Microchip TC54 Voltage Detector - Microchip Application Note Published 12-Nov-02 (app note added 2/06)

Analog Milliamp Meter Used as Voltmeter - A milliamp meter can be used as a volt meter by adding a series resistance. The resistance needed is the full scale voltage reading divided by the full scale current of the meter movement. So, if you have a 1 milliamp meter and you want to read 0-10 volts you will need a total resistance of 10/.001 = 10K ohms. The meter movement itself will have a small resistance.... [Bill Bowdewn's site]

AVR Digital Voltmeter - Most electronics hobbyists these days find a digital voltmeter indispensable. Indeed, having more than one is a positive advantage!This little project with six voltmeters in one inexpensive box therefore has some very useful features for the hobbyist. The unit is quite inexpensive, two ICs and a couple of transistors. One of the ICs is an AT90S4433 AVR..(electronic circuit added 4/05)

Ballantine 300 AC Voltmeter manual w/schematic - (manual added 07/07/07)

Battery Monitor Draws 8 µor Less - 04/13/95 EDN-Design Ideas....The battery monitor in Fig 1 nominally draws 5 µA during normal operation and flashes an alarm indicator when the battery voltage drops below a critical value. The alarm-state current depends on the desired indicator brightness, but you can easily make the current average less than 500 µA. This monitor was developed as a change-battery warning.... [Design Idea by Arthur W Du Rea Jr, Science Applications International Corp, Oak Ridge, TN]

Battery Monitor Emulates Auto Dashboard - 07/03/97 EDN-Design Ideas.... When you use battery-powered scientific-recording equipment, you must know the state of the battery, because an unnoticed battery run-down can lead to loss of data. Several types of warning indicators are available, but all have their drawbacks. Moving-coil indicators, test terminals, and digital flags, for example,.... [Design Idea by TG Barnett and J Millar, University of London, UK]

Voltage Detectors / Sensors / Monitors: #'s - B C - D E - M N - V