Nov 072018
 

How to Make a Current Flow Indicator?

This Electric Current Flow Indicator gives a visual indication that there is a current flow. Possible applications for this small circuit may be: a battery charger, a voltage power source, etc.

In order to achieve our objective we place 3 rectifier diodes in series, which in turn are in series with the load and battery. See the diagram.

How the current flow indicator works?

An “I” current flows through the rectifier diodes and there is an approximate voltage drop on them of 1.8 to 2.2 V. We have to remember that the voltage drop on a directly polarized diode can be between 0.6 to 0.7 volts. This range of voltage drops (1.8 to 2.2 volts on the 3 diodes) is sufficient for a LED to turn on.

How to make a current flow indicator

The LED brightness remains constant throughout the range of currents “I” and reaches up to a maximum of 1 Ampere for the diodes that are used (1 ampere diodes).

As the voltage drop on the 3 diodes is between 1.8 and 2.2 volts it is not necessary to use a current limiting resistor for the LED.

This Electric current flow indicator is inexpensive and reliable, however, approximately 2 volts are lost by the voltage drop across the 3 diodes. This voltage drop may not be important, but if it is, it may be taken into account in the design of the battery charger or voltage source, thus delivering 2 more volts.

This circuit does not indicate the magnitude of the current being delivered. The idea is to indicate that there is current flow. If for some reason the demanded current is greater than 1 ampere, the rectifier diodes must be replaced by higher capacity ones. See the list of components below.

List of components for the current flow indicator

  • 3  1N4001 or similar rectifier (1 ampere) (D1, D2, D3) or …
  • 3  1N5808 or similar rectifier diodes  (3 amps) (D1, D2, D3)
  • 1  common red LED (D4)
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