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I didn't find a solution in the other similar posts or maybe I don't understand them.

Here is my problem : I've got power supply with an output of 5V and 8A to feed 128 leds drawing 5V and 50mA each. At maximum effort they will draw 6.4 amps from the power supply so, I'm seeking a solution to reduce the output current by at least 1.6 amps.

In the first part of my project I'll only use 42 leds wich would draw 2.1 amps from the power supply, this mean that I have to divide the current by nearly 4 times.

In both situation keeping the voltage as near as possible to 5V is very important.

Thanks for your attention.

Amelien Bergerot
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2 Answers2

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This question pops-up regularly in different forms.

The specification mean that the supply can provide up to 8 Amps. It does not mean that it will deliver 8 Amps.

Compare it to when you say "I can lift 40 kilos".
So what if you have to lift 10 Kilos? Do you take something like sleeping pills to reduce your strength? No, you lift the 10 kilo and have power to spare.

So a supply which can deliver up to 8 amps can easily also deliver 2.1 Amps and have some spare.

Oldfart
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  • I like the weightlifter analogy, I might use that. But only in very non-academic circles, as weight doesn't have the right sort of dimensions for current, flow in the hydraulic analogy does. – Neil_UK Apr 06 '19 at 13:04
  • Thank you @Neil_UK. Initially I was thinking along the same lines as you, but in the end I went for something which non-technical people can grasp. – Oldfart Apr 06 '19 at 13:31
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Current does not work that way. If you have a 5V supply and 5V load, the load will draw only as much current as it wants, provided that enough current is available from supply.

Justme
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  • It's not that current doesn't work that way. It's that constant voltage supplies don't work that way, You could make a constant current supply that would force 8 A through its output, regardless of load, up to some maximum voltage capability. – The Photon Apr 06 '19 at 15:29