DiscoverCircuits.com, has 30,000+ electronic
circuits, cross-referenced
into 500+ categories. We have searched the web to help you
find quick design ideas.
We make every effort to link to material posted by the designer.
Please let us if you would like us to link to or post your
design.
The contents & graphics
of Discovercircuits.com are copyright protected.
LINKING to Dave's circuits is permitted but DO NOT COPY any files to your WEB
SITE server
AC
Current Monitor
The hobby circuit below shows how a small current transformer from Magnetek
can be used to monitor AC current to a load. The AC voltage developed at
the secondary of the transformer can be scaled so it can be read by any
digital multimeter. The transformer is rated at 30 amps.
DC CURRENT INDICATOR #4
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. ....
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)
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.
Low Value Capacitance Meter
This circuit was originally designed to measure the volume of fluid inside a medical
syringe. As designed, it produces a zero to 5 volt output, corresponding to
a capacitance change of about 10 picofarads. With a digital voltmeter, at its
output, it can resolve a capacitance change of 0.002 picofarads or 2 femtofarads.
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.
