I made a simple LED circuit using a battery, a variable resistor, and a LED. When the light intensity satisfied my demand (I do not need the full intensity) by changing the resistance, the condition was: R1 voltage: 0.5V LED1 voltage: 2.3V Current: 86 uA
Now, I want to add one more LED in a series to make a dual LED system. But I don't know how to calculate the appropriate supply voltage and resistor to keep the light intensity the same (= same current of 86 uA through 2 LEDs). For example, what should be the resistance if I use 4.5 or 6V supply? Any thoughts or suggestions?
Okay, now I update a new circuit to supply 5.5V using a voltage regulator. It is battery powered (6V: 4 x 1.5V AA), so I want to keep the current (or voltage) constant ( ~ 86 uA) during the period of operation. Do you think this circuit would work as intended? (Let's ignore the product error between the same LEDs)
Or what about this design for the parallel arrangement?
I want to supply the constant voltage while the battery voltage goes down. That's why I need to use the voltage regulator.