Modifying a PCB

A while ago I had some PCBs made and 3/4 projects were good. But I have that one project thatI dont use anymore and I dont want to just chuck the PCBs. So I thought of a project that I actually have that might fit that design.

Original Project
A nano with a connection out from digital pin 8 (was for a servo signal)

Nano also connects the Gnd & Vcc from a USB which was to have a resistor between them to keep a battery pack alive. I found a better way and Im not doing this project anymore.

New Project
A nano with a connection our from digital pin 8 to a mosfet gate.

Mosfet also requires some extra connections to GND, a two header pin with a diode and to vcc.

So Im thinking of doing what I drew on this image. Black is what I have and red is what I will add:

From right to left this is what I did:

  1. The resistor is not on the pcb, its just the drawing where the R would go, connecting the GND trace on one side of the PCB with the 5VCC trace on the other side of the PCB. So that I dont even need to bother with.

  2. Connected Mosfet-GATE to digital pin 8 via the hole available.

  3. Connected Mosfet-SOURCE to GND on Arduino and USB connector via the hole available.

  4. Connected Mosfet-DRAIN to a two-header pin to which I must somehow connect the diode underneath in order to leave space on the top side for my load. And then onwards to the 5Vcc of the USB connector.

Id like general comments as to what Im doing, possible pitfalls, but also, the best way to keep it as tidy as possible.

  • The mosfet I can lay flat on the PCB since I have enough space for it.

  • The two-header pin would also lay flat in order to access both top (load) and bottom (diode).

Any other pointers?

Just some general experience from doing a lot of these types of hacks:

  1. Use solid hook-up wire instead of stranded to avoid stray bits of frayed ends touching other stuff.
  • solid CATV can be cheap, but the insulation is very thin on each wire and melts off during soldering.
  • breadboard hook-up wire is my personal favorite.
  1. Soldering to components or to plated through holes is much more durable than soldering to traces or pads.
  • there are times when a trace or pad is all that is available but where possible avoid them.
  1. If you have a through-hole component of some mass, such as the Mosfet, with no holes to anchor the component
    to the board, glue it to the board.

Adding components to an existing PCB