Basically you can't measure the resistance of an LED.
Suppose you have a 3.8V LED in a simple circuit with a 9V battery supply.
You need to insert a resistor in series with the LED that will give you a voltage drop of 5.2V.
But you don't know the current that will flow through the circuit until you know the total resistance
of the circuit.
You can use a pot and adjust it from zero to determine the point at which the voltage drop across the LED is 3.8V
and then measure the current in the circuit. But you wouldn't need to calculate the size of the resistor then because
you would just measure the resistance across the pot.
But is there a way of actually calculating the size of the resistor required that will give you
the 5.2 V drop that you require?
I can't think of one. What's the normal practice?
Cheers
Suppose you have a 3.8V LED in a simple circuit with a 9V battery supply.
You need to insert a resistor in series with the LED that will give you a voltage drop of 5.2V.
But you don't know the current that will flow through the circuit until you know the total resistance
of the circuit.
You can use a pot and adjust it from zero to determine the point at which the voltage drop across the LED is 3.8V
and then measure the current in the circuit. But you wouldn't need to calculate the size of the resistor then because
you would just measure the resistance across the pot.
But is there a way of actually calculating the size of the resistor required that will give you
the 5.2 V drop that you require?
I can't think of one. What's the normal practice?
Cheers