Nexus Mosaic, providing constant power to 24 android tablets

[sean87]

Hey guys,

In last few weeks I was busy making an Android app that plays a movie divided in 24 devices. I am running the demo succesfully on 24 Nexus 7 tablets.



No I am facing a challenge! all this time I had to charge the tablets, and they usually last for few hours. Now I want to mount them on a board, so I need to find out a way to constantly provide power for them.

Each

The option of removing backplate and connect directly to a PSU is a no go, since I don't want to void the warranty, and the wifi antenna is on the backplate (The videos get synced through WiFi with a time server). Now I have some very thin right angled USB plugs that allows the tablets to be close to each other, so now I have to find a way to power up all tablets using usb port.

I did a search, and found a power supply like this: http://nl.farnell.com/tdk-lambda/ls150-5/psu-enclosed-5v-26a-150w/dp/1657459?Ntt=1657459

So my question is, is going for 2 of those supplies, and ordering some PCB mountable usb jacks and connect all them to that power supply in parallel (current divider?) a good idea?

What you would suggest in this case!? please let me know

Thanks!

[Clint]

Out of interest do you not have the supplied PSU's ?

[sean87]

Well yes, but I am thinking of a ultimate solution

[penfold]

It doesn't have to be a USB port, you can drive them all from a 20A 5V supply or two.

[NiHaoMike]

Easiest solution would be to just use the supplied chargers and a few power strips. A neater solution would be to use a PC power supply wired to a bank of USB sockets. Just tie the data lines to each other to enable full speed charging.

[Balaur]

Are the tables 2012 or 2013?
If 2012, maybe you can use the pogo charging port (left side of the device).
If 2013, you can use QI wireless charging pads (if you find them at a good price)

[dannyf]

Wireless charging if the device supports it.

[DavidDLC]

http://www.engadget.com/2013/11/19/nexus-wireless-charger/

[peter.mitchell]

You can buy somewhat decent QI compatible charge pads for about $20 USD each.

Then grab oen of these; http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_123394_-1

[mobbarley]

A couple of powered USB hubs?

[strangelovemd12]

You might need to clean up the signal from the linked PSU to protect the Nexus devises and/or get them to  function properly.  I am not sure how well everything is regulated these days, but many older USB devices would smoke if fed anything outside of spec.  Speaking of which, check this out for helpful general info.

Also be wary of using USB hubs.  USB spec says 5v 500ma per rail, so daisy chaining a bunch of hubs is bound to fry something.

[NiHaoMike]

Any good PC PSU will work just fine for that application. If anything, it would likely be better than the supplied chargers.

[ddavidebor]

A GOOD QUALITY switching power supply 5v will do that.

Absolutely not a chinese crappy one. If it fails you will have a lot of dead tablets.

You should Buy something for industry of a reputable brand and from a reputable distribuctor

Some extra protection can be a good idea, like a lot of zener in parallels and a overcurrent protection.

Also, you will need big cables, the current you need is not a joke and the voltage drop may be unaceptable.