Step 1: Design Overview
Step 2: Parts List
iPad Mini Cart Parts List
8 USB Hubs DUB-H7 7-PORT USB 2.0 HUB
$27.06 x 8 $216.48
1 Tripp Lite Power strip
$26.99 x 1 $26.99
1 Zip ties
$6.35 x 1
1 6' extension cord Industrial strength, as it gets plugged in and unplugged a lot.
$10.63 x 1 $10.63
1 Pelican 1630 Case
$203.99 x 1 $203.99
PVC Pipe used as conduit. but I think something like this monoprice wire flex tubing might have been a better choice if done over again as it lets you divide bank A and B into separate runs.
Step 3: Putting It Together Part 1
When cutting the pick N' pluck foam something long, thin and dull like the back of a long saw blade works great to separate the foam. Using the dull back lets you separate the precut foam without adding any new cuts you don’t want. Make sure to go slow and use a marker to mark off where each cut should be made. Thicker foam might be an even better option but that requires custom molding.
Step 4: Putting It Together Part 2
1. Label all cables first. This is really important so you know what cable goes to what and you don't have to spend an hour figuring this out.
2. Make sure you have your cables paired in an A-B bank or a naming system you choose but stick with it two banks of 20 each. This makes things much easier for configuring the USB hubs for cascading so the computer can see all 40 at once.
3. You can practice and not have to worry about screw ups in the cut on the first set of foam by hiding it as the bottom section of foam..
Step 5: Putting It Together Part 3
A few more tips:
Numbering each iPad on the actual unit helps quite a bit when tracking down problems.
Color coding each bank of 20 using zip ties helps keep things in order,
the iPad's will charge off the hubs but it's pretty slow so you'd want to leave them overnight.
Now sit back and reflect on how much you saved by looking at these commercial carts and saying you could build something better..
Bretford PowerSync Cart for iPad
DS-IP-TC16 Charge and Sync 16 iPads