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Circuits Designed by Dave Johnson, P.E. : |
- DC
CURRENT INDICATOR #4 December 15, 2008
The circuit below uses some common components to turn on an LED whenever DC current
above a certain level is detected. The circuit uses a very popular LM393 dual
voltage comparator from National Semiconductor and a common 1N4148 signal diode.
The diode acts as a crude 0.7v voltage reference. Only one of the comparators
inside the 8 pin package is used. A pair of resistors across the diode forms a
voltage divider, which produce a reference voltage of about 0.015v. ....
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Electrical Current Indicator
I designed this circuit as a simple current indicator
for any load ranging from 40 watts to 250 watts. The circuit turns on a small
LED, whenever it detects current flowing to a remote load.
(added 12/04)
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ISOLATED AC CURRENT MONITOR
This circuit uses a small AC current transformer from Magnetek to produce an
isolated voltage proportional to the AC current in the primary winding. The
transformer contains a single turn primary with a low 0.001-ohm resistance. It
can easily handle 30 amps of AC current and provides at least 500vac of isolation.
With the components shown, the output AC voltage is scaled so 1 amp of current
produces 100mv of AC voltage.
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Pump Motor Monitor
This circuit can turn on a light or sound a beeper, whenever an AC line powered pump
motor turns on. It is designed to detect the motor current using a small
inductor placed on the outside of the motor’s power cable. No direct wire
contact is needed.
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Links to electronic circuits, electronic schematics, designs for engineers, hobbyists,
students & inventors:
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Development of an Extensive SPICE Macromodel for 'Current-Feedback' Amplifiers -
National Semiconductor Application Note....[App Note] |
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Dual transistor improves current-sense circuit - 16-Aug-07 Issue of EDN
A two-transistor circuit eliminates variation in output due to temperature.... [Design
Idea by Robert Zawislak, PE, Consultant, Palatine, IL] |
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Errors & Error Budget Analysis in Instrumentation Amplifier Applications -
AN-539 Analog Devices Application Notes (app note added 2/06) Describes a
systematic approach to calculating the overall error in an instrumentation amplifier
application. |
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Fundamentals of Sampled Data Systems - AN-282 Analog Devices Application
Notes (app note added 2/06) |
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High Accuracy Current Sense Amplifier Enables Current Sensing & Current Sharing -
Maxim APP 391: Mar 01, 2001 / (app note added 5/08) -Current sharing between DC/DC
converter modules enables several modules to be paralleled. In recent years, tight
tolerances for current sharing have made discrete current-sense Circuit designs a
formidable challenge. This App Note describes a low-cost, space-saving and
accurate current sensing and sharing scheme using MAX4372. |
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High-side current monitor operates at High-Voltage - 22-Jul-04 Issue of EDN
The simplest technique for measuring current in an actuator or a motor is to monitor
the ground current with a resistive element between the load and the ground. Because
the device and its associated electronics share a ground potential, you need to
amplify only the ground-current signal. This approach, however, does not detect
device short circuits to ground, which can overload the high-side d.... [Design Idea
by Greg Sutterlin and Brian Whitaker, Maxim Integrated Products, Sunnyvale, CA] |
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High-Side Current Sensing: Considerations & Applications for High-Side Current
Monitoring - Zetec Semiconductors Applications Notes A guide for
using the ZXCT range of products. Contained within the note are application ideas for
extended supply ranges, a circuit for bi-directional current sensing and an
over-current/short circuit protection circuit. Now updated and contained within AN39
(app note added 2/06) |
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High-side Current-sense causes little error - 0316/95 EDN-Design
Ideas....Measuring dc would be simple if you could always reference your measurement
signals to the positive rail. Unfortunately, most current-metering applications
require a ground-referenced output. Typically, the signal that you want to measure
consists of a small differential signal that rides on a large common-mode voltage....
EDN is migrating links. This link is not verified. Search the "title" + "EDN" for
new link. |
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High-side current-sensing switched-mode regulator provides constant-current LED drive
- 14-Apr-05 Issue of EDN Drive LEDs with constant-current source....
[Design Idea by Bradley Albing, Philips Medical Systems Inc, Cleveland, OH; Edited by
Brad Thompson] |
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High-side current-sensor has period output - 7-Mar-02 Issue of EDN You
use high-side current monitoring in many battery-powered products that require
accurate monitoring of load current, charger current, or both. In applications for
nonportable designs, high-side-current monitoring serves as a power-supply watchdog
that can flag a failure in downstream devices.... [Design Idea by Greg Sutterlin,
Maxim Integrated Products, Wexford, PA] |
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High-side current-sensor monitors negative rail - 17-Apr-03 Issue of EDN
All dedicated current-sense amplifiers provide high-side sensing on a positive supply,
but you can adapt such circuits for monitoring a negative supply (Figure 1]. The
positive-supply pin, V+, connects to the system's positive supply, and the ground pin,
GND, connects to the negative supply, VEE. That arrangement monitors the negative
supply and provides a positive output voltage for the extern.... [Design Idea by Ken
Yang, Maxim Integrated Products, Sunnyvale, CA] |
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High-Voltage Current feedback Amplifier is speedy - 04/26/01 EDN-Design
Ideas....The circuit in Figure 1 powers a microparticle and nanoparticle ion trap
through a 1-to-5-turns-ratio, high-voltage transformer. It also works successfully as
a driver for a piezo-tube scanner and in a near-field scanning optical microscope. The
circuit is robust and works with supplies ranging from ±50 to ±230V.... [Design Idea
by Joseph Ting, Institute of Atomic and Molecular Sciences of the Academia Sinica,
Taipei, Taiwan] |
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Improved current monitor delivers proportional-voltage output - 19-Jan-06
Issue of EDN New, improved circuit delivers an accurate linear-voltage output
proportional to current in primary winding.... [Design Idea by Susanne Nell,
Breitenfurt, Austria; Edited by Brad Thompson and Fran Granville] |
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Improved Kelvin contacts boost current-sensing accuracy by an order of magnitude -
17-Feb-05 Issue of EDN Many power-supply designs rely on accurately sensing the
voltage across a current-sense element. Multiphase regulators use the sense voltage to
force current sharing among phases, and single-phase regulators to control the
current-limit setpoint. As internal complexity and clock speeds increase, processors
impose narrower operating margins for power-supply voltages and currents, which in
turn m.... [Design Idea by Craig Varga, National Semiconductor Corp, Phoenix, AZ] |
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Instrumentation Amplifiers Solve Unusual Design Problems - AN-245 Analog
Devices Application Notes (app note added 2/06) Traditionally Considered Only
for Transducer-Conditioning Applications, Instrumentation Amplifiers Bring Unique
Performance Benefits to a Range of Other Applications as Well. |
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Integrator Forms Picoammeter - 07/17/97 EDN-Design Ideas EDN is migrating
links. This link is not verified. Search the "title" + "EDN" for new link.
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MOSFET Current Sensing - Method of mirror current sensing a MOSFET (added
4/02) |
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Optocoupler extends high-side Current-sensorto 1 kV - 03/01/01 EDN-Design
Ideas EDN is migrating links. This link is not verified. Search the "title" + "EDN"
for new link. |
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Current Monitors / Sensors/ Detectors:
#-B C
D-Q R-Z |
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