24 Channel USB Connected LED Controller, upto 1A per Channel

Step 4 Transistors and Headers

As discussed in step 2 ,In addition to the SEL jumpers, transistor placement is based on if the transistors are set up to sink or source current. 16 Transistors(T1-T16) on one side is a set, and the 8 transistors(T17-T24) on the opposite side are a set. Each can be configured differently, see Step 2.


Transistors:
*For a set of transistors that is sinking current, the transistors are placed as seen on the top-side illustration. Transistor Pin 1(Collector) goes to hole labeled 1, Transistor Pin 2(Base) goes to hole 2, Transistor Pin 3(Emitter) goes to hole 3.

*For a set of transistors that is sourcing current. The transistors are placed opposite of the top-side illustration. Transistor Pin 1(Collector) goes to hole labeled 3, Transistor Pin 2(Base) goes to hole 2, Transistor Pin 3(Emitter) goes to hole 1.

- Start by taking a transistor and a needled nose pliers.

- Figure out what way the transistor's center pin(Base) needs to be bent. Depends on sink/source configuration.

- Grab the center pin with the needle nose pliers and bend it out a bit as seen in the images below.

- Starting with T1, insert the transistor into its proper holes 

- Work your way around the board and solder in all 24 Transistors.

Headers:

- Consider the position/polarity of the 2 pin PWR header, and place it.

- Mount the 6 pin polarized header, ExtHeader, as shown on the top-side illustration. It is used to connect other peripherals or devices to the PICs A0-A3 pins, could be used for Analog to Digital Conversion, input switches, or additional outputs.
*NOTE: ExtHeader on version 2 PCBs, one of the pins on ExtHeader is unconnected but should be connected to GND. If its required, just jump it to the nearby NEG6 select header with some wire. 


- Optionally mount the 5-pin header in the ICSP position, this is used for In Circuit Serial Programming of the PIC. (not shown on the PCB)