USB power question

[rhoelsch]

USB port from a tablet should be able to power one of these sets, right?https://www.amazon.com/dp/B076T8NF9D/ref=sspa_mw_detail_6?psc=1
 Leds are 5v. I have the non-led version and that works fine.

[Slippyblade]

Noooooo.  USB on a powered port only puts out about 500ma tops.  The port on a tablet probably puts out way less.  Even if it DOES provide that much, it's on a battery that will dramatically shorten the life.  That kit could be used on a tablet, but I wouldn't try to power the LEDs off the same device.

[rhoelsch]

So if I just purchase the led buttons by themselves, and use them with my existing board, how can I go about powering them separately?

[Slippyblade]

If you are trying to make a portable rig, I'd maybe use a separate wall wart, cut the cord, and splice directly.

[PL1]

If you use 12v LED buttons and power them with 5v, that will greatly reduce the current draw -- 5.83mA instead of 20mA per button.


Scott

[rhoelsch]

I think there may be a way to power the leds and make them blink with an arduino, as well as use that as an encoder. I'll have to do some research.

[rhoelsch]

Decided for now it's best to use a 5v ac adapter. I'm not sure what the leds are rated for, and I'm a little worried about blowing them. They're generic buttons you get from Amazon, probably made in China, along with the knockoff Sanwa joys. At any rate, I have plugs that will give me 850mA, 550mA, and 1A. I'll be lighting 6 buttons. Is there a better way to figure out what I'll need besides starting at the lowest current and moving up from there if it's too dim? I'm at a loss not knowing what they can handle.

[AndyWarne]

If you are only powering 6 buttons and they are 12V buttons powered from 5V then the current draw would be tiny, you could easily power these from USB power.

If using a wall power supply any of the 3 you mention would work. Or one rated at only 100mA would work equally.

[JudgeRob]

I try to stay in the habit of not powering anything through USB.  If you accidentally short something or pull too much power through, you've either smoked a USB port or damaged the whole device.  It's a lot easier to replace a wall transformer. 

The voltage level of your power supply will determine the brightness, not it's current rating.  You should determine if your LEDs have current limiting resistors built in.  Most of them do.  If not, add something like a 330 to each one to prevent them from sucking out too much current and burning themselves up.