Low Voltage Indicator

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Page created by T Sep 30th 2009:

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Low Voltage Indicator Circuit. Circuit and Image by T. Click to Enlargen.

==Low Voltage Indicator:==This Circuit can be used on Single Wire Alternators that have no Indicator Connection to show that the Alternator has started Charging after the Engine starts.

It can be also used on Cars with normal Alternators simply to warn that the Battery Voltage is low.

===Operation:===The Circuit only works when the Ignition is turned on because the Transistors' control Voltage comes from the Ignition Circuit.

====Low Voltage:====When the Battery Voltage is less than 11.5 Volts the right hand Transistor is allowed to turn on, allowing Current to flow through the Light Bulb. The left hand transistor is turned off because the Voltage is too low to allow current to flow through the Zener Diode.

====Normal Voltage:==== When the Battery Voltage is greater than 11.5 Volts the right hand Transistor is turned off by the left hand Transisor, preventing Current flowing through the Light Bulb. The left hand transistor is turned on because the Voltage is high enough to allow current to flow through the Zener Diode.

The left hand Transistor prevents Current from flowing through the right hand transistor by shorting its Base to Ground.

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