Electronics > Beginners
Measure current without loosing some
Kasper:
--- Quote from: haizaar on July 23, 2019, 12:00:27 pm ---
2. For power I'm using USB power supply that says it's capable to provide 2A (tested again two different models just to be sure).
[...]
No-load: 4.98v
10 leds: 4.95v
20 leds: 4.75v
30 leds: 4.60v
40 leds: 4.43v
45 leds: 4.31v
50 leds: 3.54v
Each lead can consume up to 60mA on full brightness, so with 2A power supply it should be able to power 30 leds easily.
What's interesting is that even with 50 leds and there was no noticeable drop in brightness. Hence, if every led consumes 60mA max, 50leds * 0.06A * 3.54v = 10.6W, which equals to 2A * 5V as stated on USB charger. Meaning the charger does what's written on it. It least some useful outcome :)
Thanks again everyone for your replies!
--- End quote ---
Your numbers add up nicely and that is as expected but fire and electrocution can also be expected, more so with cheap phone chargers.
It is best to keep within all the ratings even with good equipment. If it says 2A, don't try to draw more than 2A. Try to leave a bit of safety margin on top of that also. And keep in mind all the other current draws; arduino, etc.
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