Hello!
Project: LED lighting for indoor garden
I want to build a light system that is set up with four units, each consisting of three LEDs in series. Then I want the four units wired in parallel to a single power source.
Specs:
Blue LEDs:
Forward Voltage: 3.0-3.4V
Current: 20mA
Purple LEDs:
Forward Voltage: 3.0-3.6V
Current: 20mA
Power Source:
AC to 12VDC 1A LED driver
Each series or string would be comprised of: Blue, Purple, Blue, Resistor.
So I did the math and was hoping you all could double check it and answer a couple questions.
Taken from various other threads and websites, I figured 3 LEDs and one resistor per string for a 12V supply. Then I did the math and figured out I need 120 Ohm resistors for each string. Then I calculated the power for the resistors and came up with 48mW, doubled to 96mW for reliability. Question: How do I figure out which resistor to use from this figure? 1/4, 1/2 watt...etc.
Then I looked at it logically, and I'm confused. If each string is pulling 20mA current, 4 strings total, then that would be 80mA. But my power supply generates 1A, or 1,000mA? So that would be way too much. Thought I was starting to understand this stuff, but I guess not.
Your help and explanations are always greatly appreciated.
Project: LED lighting for indoor garden
I want to build a light system that is set up with four units, each consisting of three LEDs in series. Then I want the four units wired in parallel to a single power source.
Specs:
Blue LEDs:
Forward Voltage: 3.0-3.4V
Current: 20mA
Purple LEDs:
Forward Voltage: 3.0-3.6V
Current: 20mA
Power Source:
AC to 12VDC 1A LED driver
Each series or string would be comprised of: Blue, Purple, Blue, Resistor.
So I did the math and was hoping you all could double check it and answer a couple questions.
Taken from various other threads and websites, I figured 3 LEDs and one resistor per string for a 12V supply. Then I did the math and figured out I need 120 Ohm resistors for each string. Then I calculated the power for the resistors and came up with 48mW, doubled to 96mW for reliability. Question: How do I figure out which resistor to use from this figure? 1/4, 1/2 watt...etc.
Then I looked at it logically, and I'm confused. If each string is pulling 20mA current, 4 strings total, then that would be 80mA. But my power supply generates 1A, or 1,000mA? So that would be way too much. Thought I was starting to understand this stuff, but I guess not.
Your help and explanations are always greatly appreciated.