For those who own a PC or laptop without any Serial Com Port, it is still possible to use the Pic-plot by mean of an inexpensive USB to serial converter. These adaptors come in different shapes and cabling arrangements, but all of them offer the possibility, with a simple modification, to extract the 5V that is available from the USB connector. This allows to supply the Pic-plot, so that you can get rid of the AC-DC adaptor that otherwise would be necessary. You may also decide to put the modified adaptor and the Pic-plot together in a small box, then building by yourself a self-powered GPIB to USB converter.
Of course there are so many different versions on the market that we cannot describe every one. And we do not need to choose a particular one, because what they all have in common is what we need: an RS232 and an USB connector. What can be different is the work we should do to pick the 5V line to be delivered to the Pic-plot. We report here three of the possible "flavors".
What we need to do is to "steal" the 5V power from the USB adaptor to supply the Pic-plot. Therefore it is important to know the USB connector types and pinout.
Depending on the type of adaptor you have, and knowing where the 5V and the GND are available at the USB connector, you can easily make your own idea about the modifications you need. Some suggestion below are referred to the adaptors we have seen so far.
Bottom line, if you don't want to touch the USB dongle, you can just catch the the red and black wires inside an USB A-A extension or an A-B cable by carefully splitting the outer insulation.
To connect the USB adaptor to the Pic-plot you may either build a very short null modem cable or a pigtail (saving one female connector).
Pigtail wires will be soldered at the bottom side of the PCB to the indicated pins of DB9 Pic-plot connector. See the picture:
If you are using a Type2 adaptor, you may consider the possibility to cut the DB9 male of its RS232 cable and rewire as null-modem to a DB9 female that will be plugged in the Pic-plot serial port.
Pic-plot circuitry operates at 5V, but there is a 5V on-board regulator to allow the use of non-regulated wall-wart AC adaptors. To correctly supply it from the 5V taken from the USB dongle we must apply them at the IC1 regulator output. An handy point where to connect the 5V could be the jumper wire JP1 (see top overlay of the PCB). GND wire can be the same used for the serial data lines return.
The assembled USB adaptor+Pic-plot is ready to use: the whole system is self-powered from the USB-host port, so you don't need the wall-wart. Don't forget to install the Virtual Com Port drivers on your PC following the procedures described in the USB adaptor instructions. Refer to our Pic-plot pages for its configuration.
You may want to put the complete system in a plastic enclosure: you can start from here:
The projects presented in these pages are our own design and have been tested and verified by ourselves at the best we can. However, they might be inspired by concepts, ideas, solutions coming from known-art or free resources on the Web. We provide them as reference designs to skilled hobbyists and technicians who are willing to reproduce them for non-commercial use. Your results might be different from ours and we cannot be considered responsible for that. Similarly, we are not responsible for any damage or injury you might incur while building, assembling or using the equipments, projects or ideas presented in these pages. The firmware embedded in our projects is our property unless differently stated and, when available in the Download Area, it is license-free only for non-commercial purposes.
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