Power supply calculation for DIY LED lighting

**qngwn** · 9th May 2014, 22:19

For 2ft depth, you would be able to grow lower demanding carpet plants, unless you are going to use lens to focus the 3W LEDs.

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**tawauboy** · 9th May 2014, 22:45

Originally Posted by seudzar

If your driver can only supply up to 5A, it means if can supply only maximum of 5A. However if your load only draws 1A, it means your driver only supply 1A to your load.

do note that this does not apply to LED.

**seudzar** · 10th May 2014, 01:20

Originally Posted by tawauboy

do note that this does not apply to LED.

Yes it does apply to LED and I have done a couple of DIY led lightings for my 8 inch tank. I have been using a 2A 12vdc power supply to power up a 0.25A 12vdc led strip.

**Shadow** · 10th May 2014, 17:40

It possible that your led strip come with build in resistor to limit current. Normal high power led us normally sell in chip no built in resistor.

LED is prety much diode, if you know about diode characteristic, its short circuit in forward bias.

**seudzar** · 10th May 2014, 18:49

There is current limiting resistor in the led strip.

However, what I mean is that if the led is rated at 3.5v, 350mA and if your adaptor is rated at 3.5v, 2A. You can use this adaptor to power your led. Even the adaptor is rated at 2A, it will not supply 2A to your led. I think you all got it wrong.

**ynner** · 12th May 2014, 09:53

Originally Posted by qngwn

For 2ft depth, you would be able to grow lower demanding carpet plants, unless you are going to use lens to focus the 3W LEDs.

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I am looking at glosso, can this be done by this 3W LEDs.

**Urban Aquaria** · 12th May 2014, 15:02

Originally Posted by ynner

I am looking at glosso, can this be done by this 3W LEDs.

Glosso should be fine with those LEDs, its a relatively easy carpeting plant. Just ensure that they are not overshadowed by taller plants.

**tawauboy** · 12th May 2014, 22:22

Originally Posted by seudzar

Yes it does apply to LED and I have done a couple of DIY led lightings for my 8 inch tank. I have been using a 2A 12vdc power supply to power up a 0.25A 12vdc led strip.

this is true only if there is a current limiting component, ie. ballast resistor, in your LED circuit.

**seudzar** · 12th May 2014, 23:13

Originally Posted by tawauboy

this is true only if there is a current limiting component, ie. ballast resistor, in your LED circuit.

Well, it's up to you to analyze the led IV curve. The current only increase when voltage increase. If the voltage is constant, current will remain constant. The current only increase when the voltage goes beyond it's rated voltage or threshold voltage.

**Shadow** · 13th May 2014, 10:36

Hint exponential graph and DC ripple or noise.

**tawauboy** · 13th May 2014, 22:16

Originally Posted by seudzar

Well, it's up to you to analyze the led IV curve. The current only increase when voltage increase. If the voltage is constant, current will remain constant. The current only increase when the voltage goes beyond it's rated voltage or threshold voltage.

well, you can check which is more common for LED, constant current drivers or constant voltage drivers.
and, constant voltage drivers are cheaper and easier to design ...