4520 Board construction

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4520 assembly sml.jpg


Assembling the 4520 board

Parts list for 4520 board

Shown is the smaller version of the 4520 PCB, with most of the parts laid out in proper orientation for assembly.

Larger image of the smaller board

The larger board is the same, but with a "solderboard" area attached as well.

Note:

  • The regulator chip can be replaced by a jumper (red wire in the photo) if you are using a 5.0V regulated power supply
  • The anode (positive) side of an LED is usually the longer lead. + and - are marked on the PCB
  • A vertical-insertion 6-6 modular jack can also be used; just cut off the plastic tabs.
  • A 20MHz oscillator is soldered directly to the board, bu the PIC18F4520 chip is socketed.
  • The marked pin (dot) on the 9-pin SIPs is the common bus for all eight 1K resistors inside. The proper insertion for the SIP is indicated by a dot on the PCB. The SIPs go in with altenating orientation (two each way).
  • Ceramic capacitors are non-polarized and can be intalled either way.
  • The resistor near the reset switch is 4.7K (or whatever) and the resistor near the LED is 1K (or whatever).
  • The 36-pin SIP header is intended to insert into a solderless breadboard. It's under the PCB, with the longer gold-plated pins downward.


Barrel.jpg


Barrel plug conventions

As noted in the intro, you can use a regulator or not, depending if you are planning to use a >5V power supply which needs regulating down to 5.0V, or if you are planning to use an already-well-regulated 5.0V supply.

We are trying to stick to a convention of using a 5.5mm/2.5mm barrel plug & jack for 5.0V exactly, and a 5.5/2.1mm barrel plug & jack for >5V.

It's difficult to distinguish these connectors visually, but you'll find that the 2.1 plug won't fit into the 2.5 jack, thus preventing the more unfortunate error. (2.1mm and 2.5mm refer to the diameter of the pin inside.)

You can distinguish the jacks by looking straight inside. In the photo, the 2.5mm is on the left, and the 2.1mm on the right. Note the wider annular collar around the smaller pin.