Power Supply

USB chargerTo power the tablet the plan was always to take a USB car charger and wire it directly into the car 12v power. This adapter would be hidden in the dash behind the tablet. I went and found a good power supply that put out a full 2 amps on each USB port. This was very important to maximize charging of the tablet. I needed a dual USB charger because one will be used for the tablet and the second would be simply to power the LED in the Power switch. HERE is the USB charger I got. In the following video I talk about the plan for this part of the build.

As I took this thing apart I realized there was an LED light already on-board. I assumed it was being powered by 5v so I decided to snip it off at the legs and solder some wire to them and extend that wire to the LED on the Power switch.

In the following pictures you can see how I reassembled the USB charger case over the cut and soldered power supply. There are two wires coming out of the end that are for the 12v supply from the car and two other wires sticking out of the side that was for the Power LED.

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Once I put it all back together, minus the cut off pieces, and looked at it I started to feel like it didn’t really fit the aesthetics of the rest of the project. Even though it was going to be hidden in the dash behind the tablet I would always know it was just a plain old Amazon car charger hard wired to the car mains. After looking around my room and in junk drawers and boxes of old electronics parts I found an old USB charger for MP3 player or something. It was the perfect size and was a nice black square that would suit this project much better. I took it apart and went about doing a little cutting and trimming to get the circuit board of my charger to fit into it. Because of where I already added the fuse holder in the main power supply wire I had to have it sticking out of the end of the power supply case and then looping back into the side of it. I also used a Molex connector for the 12v/5v connections and had that sticking out one side also. I like it better this way. It gives me quick and easy access to the fuse for replacement and a little asymmetry is always cool, just look at the USS Enterprise. I know it’s not asymmetrical in the classic sense like the Millennium Falcon but I’m a Trekkie so what do you want!

The above pictures show the power supply in place in the dash. The two blue connectors you see are the 5v pos/neg coming OUT of the charger from the on-board LED that will go to the LED in the Power switch.


 

On the passenger side there is a 12v power outlet that is controlled by the key. This means that when the key is on or in the Accessory position the outlet is powered. My plan was to go in behind this outlet and splice into the wires for it. After doing this I was getting no power at all! I didn’t panic. I checked all my steps and still, no power. I checked everything again and the only solution that I could come to was that the outlet never worked in the first place! I had never used it before and once I reconnected just it to the power lines it still does not work. Time for Plan B; taking the power from the radio wiring harness. This was a very stressful and harrowing experience! There is no record of this process. There was very little slack in the wires which meant there was no room for error. If I screwed up a splice or cut the wire clean through there would have been no way to fix it and I would have been hours working loose the wire and unwrapping it from the bundle for repair. After finally getting jacked into a constant 12v power supply from the car (yes, I went constant power instead of accessory) guess what!? The 5v I thought I was getting from the USB charger LED did not work and the battery was not charging either! So, out comes the power supply, thank god I just have to unplug the Molex connector at this point.

So, here is the new set up… resistor in place on second USB cable to power the LED on the Power switch on the tablet. And also, SUCCESS! blue LED ring for the first time. Lastly, the power supply in the car with the USB cable for the LED and for the tablet.

 

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