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Created June 25, 2013
Last modified June 25, 2013
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Simple On-Air / Off-Air indicator circuit.


Resistor values calculated as nearest preferred value to:



Vbat = nominal battery voltage,

Vfwd = nominal forward voltage of LED at Iled,

Iled = desired LED forward current.

Simulate > Time-Domain > Run Time-Domain Simulation

Plots LED forward currents and voltages as SW2 changes over from Off-Air to On-Air.

SW1 is required to turn LEDs off when not in use.

Hover cursor over components then:

Right click > Edit Parameters to see values, expressions and parameters used in components.

Components used are for illustration only. Actual devices, values and ratings must be chosen by design.


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