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Topic: Charging USB devices directly from AC/DC adapter (Read 205 times) previous topic - next topic

camillomiller

Hi everyone, here's my current problem.

I have a setup where I need to keep both a tablet and a card reader always powered up. They both have a USB input for charging purposes.

The setup is a bit complicated and I can reach it only with a DC plug.

Currently I use that to power an active USB hub, but it's not enough. The usb hub outputs 500mA max per port, and that's not enough to keep both devices charged.

I was wondering: can I just use a more powerful adapter (like 5V-3A) and connect it directly to 2 USB female ports in parallel, then connect the devices to the port?

I'd obviously wire it up so that the ports will only get the 5V, no data needed.

Is that feasible? Theoretically the two ports will have a nominal max output high enough for the devices to draw the current they need (should be 1.2A for the tablet and 1A for the card reader).

I'm a bit worried about the possible risks of such a setup.

I'm also open to suggestions.

Thanks!

P.s. i tried to look for different USB hubs with charging ports, but they're all too big and they won't fit inside my current tablet + card reader setup.

Paul__B

Currently I use that to power an active USB hub, but it's not enough. The usb hub outputs 500mA max per port, and that's not enough to keep both devices charged.
"Unusual" I have to say - most that I have looked at - the cheap ones - have all 5V points connected fairly directly together so as long as you power it with a proper 2 A or 3 A adapter, the devices will just take what they need.

Exception may be Apple devices - they expect secret communication with the charger and misbehave if they do not get such.

In any case, just using a "Y" cable or making one will generally work.

camillomiller

Thanks for your answer.
So basically I can solder together something like this (see the picture) and expect it to work properly?

Should I be aware of any fire/safety hazard because of the slightly high amperage if I'm using such a solution in production?


 

Paul__B

Thanks for your answer.
So basically I can solder together something like this (see the picture) and expect it to work properly?
If you get the connections right, certainly.

Should I be aware of any fire/safety hazard because of the slightly high amperage if I'm using such a solution in production?
Safety hazard is no different from a separate supply to each device using the same model power supply.  You figure.

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