Building the circuit board
[Should have everything plugged in, TPad and battery attached, PIC programmed at the end]
These instructions are for powering the TPad Fire from a two jack USB battery. As an alternative, you can power your TPad Tablet directly from wall power with 5V power supplies (1A minimum output) or use a different battery. We used right and left angle USB “A” connectors because they fit nicely in our case.
– Printed circuit board
– Electrical components- see bill of materials
– Magnet wire (28AWG)
– Heat conductive paste
– USB A cable (right angle optional)
– USB A cable (left angle optional)
– USB micro (left angle optional)
– Wire stripper
– Soldering iron
- Solder PIC, capacitors, resistors, oscillator, gate driver, mosfet and reset switch into place. Each is labeled on the board. [Picture]
- Apply heat conductive paste to back of the amplifier and clip heat sink onto amplifier and bend pins so that they fit into the holes with the heat sink resting flat on the board. Solder amplifier to board. [zoom shot of amplifier]
- Wrap the inductor with 16 loops of magnet wire. Scrap off the coating from the ends of the wire and solder into place. Check for conductivity with multimeter.
- Cut the Left and Right USB A cables leaving approximately 18cm of wire. Strip the ends of the red and black wires and trim the other two back. [Picture]
- Cut the micro USB cable leaving ~25cm of wire. Strip all four cables. [Picture]
- Solder the TPad power and USB cable to the board, first running the wires up from the bottom of the board through strain relief holes. [Picture]
- The output amplifier requires tuning capacitors. Solder a 10nF and a 3.3nF capacitor into the capacitor locations next to the “High Voltage” section of the board. [Picture]. These are default tuning values. If you want better performance from the TPad, see the Programming and Tuning section for instructions on how to pick precise capacitor values for your specific TPad.
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