PL2303HXD USB-TTL adapter for PGT Controller - Power wiring modification

The PL2303HXD is a USB to TTL UART converter module available on ebay and AliExpress for about $3. I bought one of these adapters to connect my PicGoto V4 2018 Telescope Controller to the laptop PC for direct USB-TTL serial communication. I wanted to make this converter module entirely embedded in the PGT box to become part of the Controller effectively but this was not possible due to the relative small dimensions of the plastic container I chose for the Controller. So to still having the USB-TTL module completely dependent on the PGT eletronics, I decided to make a mod to the module wiring so that it becomes active only if powered by the PGT Controller (it is operative only when the Controller is powered on). The mod is fairly simple and only requires to cut and extract the module power pin (USB side) and connect the corresponding board's pin to the 5Vin wire coming from the PGT Controller box, by soldering a short wire as shown in the following pictures.


If you don't like to deal with this mod, you can still use the unmodified PL2303HXD adapter for use with the PGT V4 2018 Controller but in this case you have to cut small copper trace in the PGT Controller PCB. It's the one label CUT on the bottom of the board.
Please, be careful ...

  • Open and remove the module plastic enclosure. Cut and extract the VCC USB pin from its housing:
  • Desolder the VCC red wire from the board (TTL side):
  • Solder a short wire between the board's 5V pin (USB side) and the cable's red wire:
  • Put back the module board in its original enclosure:

  • To connect the module to my PGT V4 Controller properly follow the following wiring allocation in the RJ9 connector:
In this way the USB-TTL adapter is powered by the connected PGT Controller box only and it opens a COM communication port only when PGT box is powered.

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December 2018