I did notice the voltages in the image. I appologize for my ignorance, though, as they do not answer my questions above. Does VR2 change the voltage of pin7 to 6.2V?
hi,
Consider when:
#1. VR3 is set to 0R and VR2 is set to 0R, the current thru the LED's will 11.5mA.
[Pin 7 will be 1.25V and pin 8 at 0v]
#2. VR3 is set to 0R and VR2 is set to 200R, the current thru the LED's will 9.9mA.
[Pin 7 will be 1.25V and pin 8 at 0v]
#3. VR3 is set to 5KR and VR2 is set to 0R, the current thru the LED's will 16.7mA.
[Pin 7 will be 6.48V and pin 8 at 5.23v], NOTE: still a 1.25V difference between pins 7 and 8
#4. VR3 is set to 5KR and VR2 is set to 200R, the current thru the LED's will 14.4mA.
[Pin 7 will be 5.71V and pin 8 at 4.46v], NOTE: still a 1.25V difference between pins 7 and 8
In your circuit as pin8 is linked to pin4, this means that LED#1 will light when the voltage on pin5
becomes ~4.46V and led#10 will light when pin5 voltage is ~5.71V.
So looking at the above 4 conditions, LED#1 will light when the voltage on pin5 approx equals that on pin 4
and LED#10 will light when the voltage on pin5 approx equals that on pin6
VR2 and VR3 do interact with each other as you adjust them.
NOTE: the markings on the LED's from 10.5v thru 15v are the attenuated battery voltage levels, the actual scale is
ONLY 1.25V, so each LED lights on a 1.25v/10 = 0.125V increment.
When set up, the circuit should indicate your battery voltage from 10.5V thru 15V.
The 39R 1Watt resistor is important if you dont want to fry your LED's.