Dustin Smith
- Jun 27, 2012
- 52
- Joined
- Jun 27, 2012
- Messages
- 52
My question is, why are my reading so close together?
I was under the impression that if I used 1 white LED rated at 3.6V, 20mA, and added another of the same in parallel, that it would double the current. But this is not the case.
The Circuit..
A breadboard with a steady power supply of 5.11DCV.
1-8 white LEDs in parallel with the resistance controlled by a potentiometer set to 70 ohms. (70 ohms being the recommendation by an LED wiz calculator at 5.0V)
I took readings across the LEDs for voltage and after the power supply board for the current. So I believe the current readings are what the potentiometer and LED(s) were using and not included the power supply. Please let me know if I'm measuring incorrectly.
# of LED mA V
8 29.85 2.89
7 29.73 2.9
6 29.39 2.93
5 28.69 2.96
4 28.51 3.0
3 27.74 3.05
2 24.65 3.26
1 23.54 3.45
And to add a further note, I did a test of the current in AC where the power is being supplied and I got a current reading of 8 LEDs of only 27mA. It's less than what my reading said I was using in DC with only the LEDs and the potentiometer! I'm lost.
I was under the impression that if I used 1 white LED rated at 3.6V, 20mA, and added another of the same in parallel, that it would double the current. But this is not the case.
The Circuit..
A breadboard with a steady power supply of 5.11DCV.
1-8 white LEDs in parallel with the resistance controlled by a potentiometer set to 70 ohms. (70 ohms being the recommendation by an LED wiz calculator at 5.0V)
I took readings across the LEDs for voltage and after the power supply board for the current. So I believe the current readings are what the potentiometer and LED(s) were using and not included the power supply. Please let me know if I'm measuring incorrectly.
# of LED mA V
8 29.85 2.89
7 29.73 2.9
6 29.39 2.93
5 28.69 2.96
4 28.51 3.0
3 27.74 3.05
2 24.65 3.26
1 23.54 3.45
And to add a further note, I did a test of the current in AC where the power is being supplied and I got a current reading of 8 LEDs of only 27mA. It's less than what my reading said I was using in DC with only the LEDs and the potentiometer! I'm lost.