Pocketbrain

Parts:

• The case came from a laser/pen/stylus that I bought at RadioShack.
• Charging socket from RadioShack. $2.59 for a 2-pack. I had it on hand already.
• 7805 +5VDC regulator was from RadioShack: $1.69
• Plug from RadioShack, was taken from my USB hub/charger adaptation. $2.59 for a 2-pack.
• 6-AA battery holder from jameco grab bag. :-)
• Batteries from Target. Ray-O-Vac 2500mAH-AA, $8.99 for a 4-pack. No sales tax, hurricane tax holiday! Extended cost for 6 batteries = $13.50.

Total cost: $17.78. Or you could consider it $20.00 for the parts that came from supply.

Materials:

• Wires and Silver-Tin solder on-hand.
• Rubber grommet. From on-hand, came in a pack of 50 or so, individual cost quite low.
• Nuts and bolts from on-hand.
• Heat transfer compound.

Tools:

• Solder gun.
• Nibbling tool.
• Drill with bits.
• File or wire brush.
• Screwdrivers.
• Safety Goggles.
• Gloves.

Safety:
Wear goggles to protect your eyes from splashes of molten solder and stray bits during drilling/deburring.
Wear gloves to protect from sharp metal bits during drilling/deburring.

Schematic



Procedure:

• Prepare the case. Drill holes for:
  - Retainer screws for battery pack
  - Mounting screw for regulator.
  - Charging port. Use nibbling tool for square end.
  - Cable. I slotted this one; just slip the grommet in with the top off.
• Test-fit battery holder, measure and cut wires.
• Solder connections according to schematic.
  - Be sure to fit the grommet and tie the wires in a knot (prevents cable from coming out) prior to soldering output cable.
  - Solder wires to the charging socket and output plug (wires + plug = cable) before attaching them to the regulator.
  - Attach battery terminals to regulator leads.
  - Now attach input (socket) and output (plug) wires to regulator leads.
• Install battery holder.
• Apply heat transfer compound and install regulator.
• Install charging socket.
• Install grommet.
• Install fully-charged batteries.

Results:

Assembled, but without socket and grommet holes:


Top off, socket and grommet installed:



Top on, fully assembled:



Detail of the output (grommet and cable) and input (socket) ports:



Close-up of the socket. Note the hole is a little bit jagged: I need a little practice with the nibbling tool!



It's not just for charging your Axim.
Shown here, it is running my Asus WL-HDD and I'm playing Monty Python, the Ministry of Silly Walks on my X50.