Troubles powering wall-mount tablets (for Action Tiles) using a voltage converter and custom wiring

This isn’t a ST or Action Tiles issue, but I am hoping some people here can point me in the right direction. I have installed a few tablets around the house that are powered using existing low-voltage alarm wiring that was in the walls, but I have 1 more tablet that I want to install in a place that doesn’t have any of this wiring in the walls already.

There is a wall switch (with common wire in the gang box) there, so my plan was to wire in a small AC-DC power converter that takes the 120VAC and outputs 1A@5VDC, then run low voltage wiring carrying that up in the wall to a low voltage gang box 6" above that gang box where I would mount the tablet. I bought some right-angle micro USB connectors to solder on to the low voltage wire for this purpose so I could keep the tablet plugged in while its in the mounting bracket on the wall.

I decided to try it out once I got the equipment, so I soldered up one of the USB connectors (just connected VCC and GND- didn’t connect any other pins in the plug) and wired the AC end of the AC-DC converter to a plug. When I plug this micro USB connector into the Kindle Fire tablet, it starts to charge. Success! Except then I started noticing the tablet was becoming unresponsive to my input. I unplugged the USB, and it immediately became responsive again. I tried a standard wall-wart, and the tablet was fine. It just goes wonkey plugged into this custom charger. Uh oh!

My first thought was that I might have contacted VCC or GND to D+ or D-, so I checked with my multimeter on a USB breakout board. But there is no continuity between VCC or GND and any of the other pins in the connector, so thats not it. And I measure 5.12 volts DC between VCC and GND, so the power looks okay.

I’m kinda stumped here.

Try the following link to see threads that people have put under project reports on dashboard projects. Quite a few of them have to do with different powering options.

My first thought is there’s a reason that tablet and phone manufacturers tell you to use authorized cables and chargers. I think you’ve just Jerryrigged too much of the setup. Just install a socket with a USB charger port and then run a regular cable to your tablet. You can put raceway over it if you want a more finished look or paint the raceway to make it less visible.

But again, look at the options that other people have used. There are a lot of different configurations that people have used, but very few of them require soldering. :wink:

What size fire tablet are you trying to power with that adapter? Because the Kindle Fire tables need about 1.5A min. So, your AC-DC converter isn’t powerful enough. You also have to be careful about the length and quality of the wire you are using. A lot of low-voltage cable isn’t going to handle enough of the current to be able to charge it well. That might also be true of the right-angle micro-usb you have. If it is intended for Sync only then it won’t have stronger, thicker power lines and won’t be useful for charging a fire tablet.

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This is a Fire HD 8. I think it ships with a 5W adapter so I figured I was good with 1A. And I grabbed some 24 gauge solid copper wire, so the ampacity should be enough for 1A.

Maybe I’ll just buy a recessed gang box and wire up a 120V receptacle behind the tablet instead of this voltage converter. Its probably safer anyway.

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