Nabis are great Android pads meant for children. They are tough and durable, and come with some great parental control features. Unfortunately, they have one big weak spot, the cable can be easily broken and is kind of expensive to replace. It is a proprietary cable. Standard USB on one end, but some strange connector on the other. It really took my kids over a year to finally break theirs, but they did. And seeing they are $18 a piece from Nabi, I decided to find something else.
I found a DIY inductive charger on Adafruit, so I decided to give it try. And YES it does work. It isn't a very high powered charger. 500 milliamps. But hey, the kit is half the price of one cable. And it should be harder for the kids to damage. It's not a cell phone, they aren't going to be hauling them around all day. So if it takes over night or all day while they are at school to charge, fine with me.
For this Instructible you will need:
An inductive charging kit.
Availible from Adafruit. INDUCTIVE CHARGING SET
Two small flat blade screwdrivers
A small Phillips screwdriver
Soldering iron and solder
Hot melt glue gun, or two sided tape would work too.
9v power supply
Step 1: Determine the Cable Pin Out
The first thing I did was to dissect the stock Nabi JR cable to determine how it was wired. One end is a standard USB connector. The other is a proprietary connector from Nabi. I first removed the USB side to check the color coding. It did wind up being standard USB color coding, black, red, green, and white. I then did the same to the other end of the cable. As it turns out, the USB part is one side of the two sided connector. The red power wire makes contact with the first three pins on its side. The ground makes contact with the first two on its side, and the metal jack case. The green and white wire each only contact one wire, but we don't really need to worry about those two.
Yup, I broke the black and green off trying to get it apart.
In the picture, the wiring wound up being as follows, from bottom to top in the pic:
- Black --- ground
- no connection
- green --- USB Data +
- white --- USB Data -
- red --- V+
Step 2: Disasembly
Remove the red rubber bumper.
Take the two small flat blade screwdrivers and slowly and nicely work your way around the Nabi prying the two halves apart. The back is the female half, and the front the male. So lay it face down and gently insert one screw diver in between the two halves. I found it easiest to start near the opening for the stylus (most people don't know it's there, it is covered by the bumper most of the time.) Pry the front half of the case out a little. Work your way around.
Do the area by camera last. Behind the camera, there are two spots that are easiest to get to from the inside. Working with the screw driver you can pry them from the inside side.
Remove the screen cable. It is the longer flat ribbon cable by the battery. It is really hard to do with out breaking it. Gently, slightly pry the white sides out and remove the black wedge. Then slide the cable out of the connector.
For the last parts, none need to be unwired from the main board, just removed from their mounting sockets so we can get to the bottom of the board.
Remove the speaker on the opposite side (farthest away from) of the USB connector ans SD card slot from it's socket.
Remove the mic from its socket.
remove the camera from its socket.
Now take the main board and stand it up so the connectors are pointing down. You don't need to completely remove it.
Step 3: Solder the Wires to the Board
With the board standing up, you need to solder the + red wire of the inductive charger to the right three pins that are closest to you. There are two rows of pins there. So if you go heavy on the solder, it will be easy to short it to the back row. A light touch is the best.
Also, all three pins are connected inside the plug. So you really need to make good contact with only one. To be safe, try to use only the outside one or two. I used two.
For the black ground wire, it's easiest to just use the ground lug on the side of the connector. It's really a mounting lug, but will work, and tons easier than the little pins.
Step 4: Reassemble the Board.
Replace all the parts in the Nabi.
Don't try putting the back half on yet.
Bring the leads for the charger out on the right. There is a indentation in the board that works nicely for routing the wires.
The hard part is replacing the screen cable. Make sure you are trying to put the black piece in right side up. It seems like the 45 degree angled part face down. It does take some force to pop it in. And it needs to be flat.
With two sided tape or hot glue mount the PCB. I placed it next to the battery. Let the pickup flop free for now.
Step 5: Prepare the Back Half of the Case
In order for it to work right, the pickup needs to be on the outside of the case. I originally tried placing it on top of the battery inside the case. But when I tried charging it, it didn't work. The two copper coils need to be as close as possible for best results. I think there is just too much distance if you try to place it inside the case.
Take the case outside, or be prepared to vacuum.
Take the hacksaw and remove all the little square thingies from the back of the Nabi. We need it to be nice and flat.
Then take and make a slot in the case for the pick up to fit through. Just above the rectangular part on the same side as the PCB is. It wound up being next to the serial number sticker on mine.
Step 6: The Rear Case
Now take the pickup and run it through the slot you cut.
Snap the rear case half back into place and re install the screws.
I used hot melt glue and glued the pick up in place. Try to get it in the center of the Nabi.
I really glued it well. Make sure it never comes off.
Also cover the two wires in a layer of glue to hold them in place.
Next use the hot melt to seal the slot. If you take your time and do two or three passes, it won't run into the slot. Do one pass down one side of the slot. One down the other. Then one in the middle if needed.
After gluing I also put a layer of packing tape over the pickup for extra protection.
Step 7: The Base
Now you need to construct a base for the transmitter. You can make this just about any way you want. Or find something to retrofit to use. I made mine out of balsa. This is for kids. So a stand that kind of forces the transmitter and pickup to line up is best. A mat would work too.
My base holds two Nabis. I have two kids, each have their own.
Then hook up the transmitter to the 9v DC power supply.
Step 8: THAT'S IT
And we're done. YAY!
Once powered, you simply have to place the Nabi on the stand so the two copper rings are as close to each other as possible. And it should start charging.
If you Nabi has been down a bit and has a REALLY dead battery be prepared to wait a bit. It may take an hour before you can even get the charge screen to come on. Another after that before it will have enough charge to come on.
Like I said, this is a small 500 ma charger. It wont charge fast, but it does charge.
Step 9: To Do
I'm think on mine I would like to add a regulator so I can use it in the car on long trips.