bob0816
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- 4
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- Sep 29, 2020
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I want to built an LED grow light from scratch but I'm not sure what to look for when wiring in series and parallel on the same board.
I want it to have different types of LEDs with different wavelength, like the Spider Farmer SF4000 or the SSK-272-RR-V2 for example, so I have to deal with different voltages and currents needed.
What do I have to look for when wiring series (of LEDs) in parallel when it comes to the forward voltage U_f (V) and forward current I_f (A) of the loads?
I tryed to find a schematic but didn't so I tryed to look for the paths in the LED light PCB. From the SSK-272-RR-V2 I could see a lot of them in the pictures found online and so I made a scetch. Here the simplistic schematic as I guessed it:
Installed are:
256 Nichia 757, NFSW757H-V1 [U_f: 2.84 V, I_f: 65 mA, I_max: 180 mA] warm whites (black squares) and
16 Cree XP-G3, XPGDPR-L1-0000-00F01 [U_f: 1.99 V, I_f: 350 mA, I_max: 1.5 A] 660 nm "photo reds" (red squares)
Then I tryed to calculate and see how they did it.
The whites are wired in series of four, the reds parallel in four.
When I look at one quart of the board and would try to drive it, my thoughts are:
- in parallel wiring, every row sees the same voltage U, so to run them, I have to put at least 11.36 V on the circuit because of the series of whites adding up (4x 2.84 V = 11.36 V to deliver U_f)
- that means that the reds will get 11.36 V in parallel too, the U_f of this part is just 1.99 V as of parallel wiring but the I_f is 1.4 A (4x 350 mA)
My question now is (if I am right so far is another one): where does more energy travel? The way of lower current needed, or the way of lower voltage needed?
I tryed to find the way of least resistance (literally) and calculated R=U/I:
series of 4 whites: 11.36 V, 65 mA -> R=174.77 Ohm
parallel of 4 reds: 1.99 V, 1.4 A -> R=1.42 Ohm
so in my mind there would be much more current flow through the red LEDs in parallel, maybe with a CC driver set to 1.5 A on a safe level (because it could take 4x I_max: 1.5 A=6 A), but the white LEDs would run way under there capacity.
What do I have to take in account when planning such a circuit regarding different V_f and I_f values?
Where am I wrong? I think have miscalculated the resistances (1/R=1/R_1+1/R_2+1/R_n)
I want it to have different types of LEDs with different wavelength, like the Spider Farmer SF4000 or the SSK-272-RR-V2 for example, so I have to deal with different voltages and currents needed.
What do I have to look for when wiring series (of LEDs) in parallel when it comes to the forward voltage U_f (V) and forward current I_f (A) of the loads?
I tryed to find a schematic but didn't so I tryed to look for the paths in the LED light PCB. From the SSK-272-RR-V2 I could see a lot of them in the pictures found online and so I made a scetch. Here the simplistic schematic as I guessed it:
Installed are:
256 Nichia 757, NFSW757H-V1 [U_f: 2.84 V, I_f: 65 mA, I_max: 180 mA] warm whites (black squares) and
16 Cree XP-G3, XPGDPR-L1-0000-00F01 [U_f: 1.99 V, I_f: 350 mA, I_max: 1.5 A] 660 nm "photo reds" (red squares)
Then I tryed to calculate and see how they did it.
The whites are wired in series of four, the reds parallel in four.
When I look at one quart of the board and would try to drive it, my thoughts are:
- in parallel wiring, every row sees the same voltage U, so to run them, I have to put at least 11.36 V on the circuit because of the series of whites adding up (4x 2.84 V = 11.36 V to deliver U_f)
- that means that the reds will get 11.36 V in parallel too, the U_f of this part is just 1.99 V as of parallel wiring but the I_f is 1.4 A (4x 350 mA)
My question now is (if I am right so far is another one): where does more energy travel? The way of lower current needed, or the way of lower voltage needed?
I tryed to find the way of least resistance (literally) and calculated R=U/I:
series of 4 whites: 11.36 V, 65 mA -> R=174.77 Ohm
parallel of 4 reds: 1.99 V, 1.4 A -> R=1.42 Ohm
so in my mind there would be much more current flow through the red LEDs in parallel, maybe with a CC driver set to 1.5 A on a safe level (because it could take 4x I_max: 1.5 A=6 A), but the white LEDs would run way under there capacity.
What do I have to take in account when planning such a circuit regarding different V_f and I_f values?
Where am I wrong? I think have miscalculated the resistances (1/R=1/R_1+1/R_2+1/R_n)