# Power calculation

Discussion in 'Power Supplies' started by dpavisic, Jul 27, 2014.

1. ### dpavisicFull Time Elf

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I have the following lights and am just wanting to check my calculations for how much power they will use and what power supply I will need.

http://www.aliexpress.com/snapshot/6008549881.html. These lights are 12 v

According to the website they use 0.30 watts per light so for every string of 100 they will use 3.0 watts. If I use a 600watt power supply @80% load this gives me 480 watts of usable power. In other words I should be able to run around 160 strings (with suitable power injection) from the one power supply.

This seems like a huge amount of lights from the 1 p/s but I would like someone to please confirm this as power is not a strong point for me. I think I followed the formula in the 101 manual but maybe I stuffed up somewhere.

Many thanks

2. ### David_AVDBite my shiny metal ass!Community Project DesignerGenerous Elf

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Umm... 100 x 0.3W = 30W, not 3.0W but may be a typo so you'll have to revise that calculation.

I made a LED current calculator that may be of interest. it's on my web site here.

I don't know if I'd trust the wattages quoted on Ray's site.

3. OP

### dpavisicFull Time Elf

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Umm no that was not a typo and was exactly the mistake I could not see. Feel like an idiot but at least I got a calculator for future reference

Thanks so much

4. ### davrusSilent Elf

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You will be safer using 0.6W for each node. In real life, 100 pixels will use about 5.5 A when all are white. (I am just testing mine right now). So I calculate 6A as the draw for 100 pixels when sizing my power supplies.

5. ### David_AVDBite my shiny metal ass!Community Project DesignerGenerous Elf

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My calculator shows the 2811 strings to be 5.55A per 100 pixels, so that's good to get confirmation with a real world example.

6. OP

### dpavisicFull Time Elf

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David your site is fantastic and full of very useful ideas.

Thanks again

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Not strings but strips (should be close) I measured 3.3 to 3.6amps with all white, center fed between two one meter sections of Plasma Icicles.

So actual per meter of WS2812 (5v) strips was 1.15-1.3amps per meter (including drop for connectors, cable and flexible PCBs), no more than one meter length from any power injection.

8. ### David_AVDBite my shiny metal ass!Community Project DesignerGenerous Elf

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Obviously any strip figures will vary a lot depending on how many LEDs per metre.

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