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LED power supply
PL1:
--- Quote from: jaharr01 on July 05, 2014, 02:27:41 pm ---Yes I can,I can use a switchable power supply. It also has 5V. Will they be less bright at 5v?
--- End quote ---
If you use the 12v resistor value (22 ohms) with a 5v input voltage, it will probably be noticably dimmer on your setup.
Run the calculator again to determine the correct resistor for 5v.
12v with a 22 ohm resistor and 5v with the proper resistor will be the same brightness because the calculator is figuring out what value/wattage resistor will provide the maximum desired voltage/current at the LED.
Scott
jaharr01:
Solution 0: 1 x 5 array uses 5 LEDs exactly
+5V
+ -|>|- -/\/\/\- + R = 3.9 ohms
+ -|>|- -/\/\/\- + R = 3.9 ohms
+ -|>|- -/\/\/\- + R = 3.9 ohms
+ -|>|- -/\/\/\- + R = 3.9 ohms
+ -|>|- -/\/\/\- + R = 3.9 ohms
The wizard says: In solution 0:
each 3.9 ohm resistor dissipates 624 mW
together, all resistors dissipate 3120 mW
together, the diodes dissipate 7200 mW
total power dissipated by the array is 10320 mW
the array draws current of 2000 mA from the source.
I can do it 5v it's not a problem
jaharr01:
And I ran the 5v for 15 channels and it was still 3.9
PL1:
--- Quote from: jaharr01 on July 05, 2014, 10:17:56 pm ---And I ran the 5v for 15 channels and it was still 3.9
--- End quote ---
If you are getting the same value resistor for red as you're getting for green/blue, you're not entering the proper values into the LED calculator.
3.9 ohm ==> 5v supply, 3.6v LED voltage (blue/green), and 400mA current draw (red) -- this will over-volt the red channels and over-amp the blue/green channels causing the reds to blow quickly and probably the blues/greens, too.
Calculate one group at a time -- channels that need the same voltage/current will use the same value/size resistor.
The values I plugged into the LED calcualtor are highlighted in red in case you want to adjust them.
Group one -- Red channels: (5 total channels)
Power supply voltage: 5v
LED DC Forward Voltage (VF): Red: 2.0-2.5Vdc
LED DC Forward Current (IF): Red: 400mA
* You will need 6.8 ohm 2 watt resistors.
* Each 6.8 ohm resistor consumes 1088 milliwatt.
* The array draws current of 2000 mA from the source.
Group two -- Green/Blue channels: (10 total channels)
Power supply voltage: 5v
LED DC Forward Voltage (VF): Green: 3.2-3.6Vdc, Blue: 3.2-3.6Vdc
LED DC Forward Current (IF): Green: 350mA/ Blue: 350mA
* You will need 4.7 ohm 1 watt resistors.
* Each 4.7 ohm resistor consumes 575.75 milliwatt.
* The array draws current of 3500 mA from the source.
The 5v power supply needs to be able to handle a current draw of up to 5.5A (2000 mA + 3500 mA) which corresponds to all channels at full brightness.
5v
| /-- Red 1 LED--- 6.8 ohm -- LED controller channel 1
|--- Green 1 LED--- 4.7 ohm -- LED controller channel 2
| \--- Blue 1 LED--- 4.7 ohm -- LED controller channel 3
|
| /-- Red 2 LED--- 6.8 ohm -- LED controller channel 4
|--- Green 2 LED--- 4.7 ohm -- LED controller channel 5
| \--- Blue 2 LED--- 4.7 ohm -- LED controller channel 6
|
| /-- Red 3 LED--- 6.8 ohm -- LED controller channel 7
|--- Green 3 LED--- 4.7 ohm -- LED controller channel 8
| \--- Blue 3 LED--- 4.7 ohm -- LED controller channel 9
|
etc.
Scott
jaharr01:
oh i understand now I ran them all the same.
Thanks
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