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How-to-guides - Understanding diodes


What is a diode and what can it do for me?


Understanding diodes.


That little semiconductor can get you out of a lot of trouble when you need it. This one way traffic controller for electronics can be used to isolate door triggers to changing an ac voltage to dc.


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Understanding Diodes


Diode Applications







What's a diode?


Diodes are electronic components which have the ability to allow current to flow in only one direction.


There are many electrical systems circuits which use diodes to prevent a back feed between circuits to isolate the circuits and to prevent some current spikes.


Diodes are ideal for isolating an alarm, keyless entry, or remote start from the factory wiring in vehicle.

Diodes are small cylindrical shaped components which are consisted of two leads, the Anode and the Cathode.


The Cathode is the striped side of the diode.


Usually a diode is black in color with a gray stripe, marking the Cathode side of the diode.


Current will flow through a diode in one direction only.

When the Anode side of the diode is facing towards the positive source of voltage, it will allow the circuit to be completed, and is considered Forward Biased.


If the Cathode side of the diode is facing towards the positive source of voltage (Anode towards negative source), then the diode will not allow the circuit to be completed.






Diode applications


The following diagrams give an example of a circuit.


Conventional Current Flow and Electron Flow.


According to Conventional Current Flow, current flows from positive to negative in the direction that the voltage drops across the resistance, or the “load”, in the circuit. According to Electron Flow, current flows from negative to positive in the direction that the electrons flow. 


The Conventional Current Flow theory seems to be the most popular and is used more often, therefore, the diagrams in the following examples will be based on the Conventional Current Flow Theory.





Diode vehicle security system applications


The following diagram illustrates how a diode can be added to a factory circuit to isolate the alarm or other device so that, when activated, it will power just one of the components in a circuit instead of all the components in the circuit.



For example, in the circuit illustrated to the left, the factory switch controls both bulbs because the current is flowing through the circuit when the switch is used to power the circuit.















The same diode in Figure #2 could be considered Reverse Biased, when the switch is off and the alarm is activated, because it is allowing the alarm to power only one bulb and is blocking the current from back feeding to the other components in the circuit.



















Continue to Diodes Part 2







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