I have 3 AA 1.5V batteries powering a strip of 40 LEDs that I bought (4.5V total)
I would like to calculate the current and/or voltage on each LED to find out approximately what values we are talking about.
I think the strip of LEDs is in parallel (I attach the photo) but I would like your confirmation.
If they are in parallel, I would like to find the current on the first LED.
Drawing the schematic with Vdc, 15 ohm resistor (it's in the box with the batteries) and all the LEDs in parallel I apply ohm's law to the first link (the rectangle you see in this figure)
I = (4.5  Vdiode_forward) / 15
How can I calculate the value of the current on D1 if I do not know the value of its forward voltage ?
Similarly ... how can I calculate the D1 forward voltage if I don't know the value of the current?
I could assume that, normally, a yellow LED supplied with 5V has a Vf=2V ... so from the calculation I would have 166mA of current ... seems a bit too much!
I would like to calculate the current and/or voltage on each LED to find out approximately what values we are talking about.
I think the strip of LEDs is in parallel (I attach the photo) but I would like your confirmation.
If they are in parallel, I would like to find the current on the first LED.
Drawing the schematic with Vdc, 15 ohm resistor (it's in the box with the batteries) and all the LEDs in parallel I apply ohm's law to the first link (the rectangle you see in this figure)
I = (4.5  Vdiode_forward) / 15
How can I calculate the value of the current on D1 if I do not know the value of its forward voltage ?
Similarly ... how can I calculate the D1 forward voltage if I don't know the value of the current?
I could assume that, normally, a yellow LED supplied with 5V has a Vf=2V ... so from the calculation I would have 166mA of current ... seems a bit too much!
Attachments

83.4 KB Views: 4