Referring to this question: How can I convert a 2 prong connector to USB?

I have decided to go with this solution: (2) You could use a cheap (from $5) serial to USB adaptor and wire the switch to eg the CTS line. This can be detected by a PC program. (answered by Russell McMahon)

My questions are what type of wiring should i use? (links anyone?) I've decided to go with this adaptor:


How would I connect the actual wires to the serial cable? from this video: http://www.youtube.com/watch?v=2MlJCMdD8MU (45 seconds)

It appears I need to wire pins 1 and 4. But I can't seem to find the shown serial adapter that would let me solder the wires into a serial port. Does anyone know where I might get such an adaptor? Or could I just connect the wires directly into the serial port pins?

Thank you all for your expertise and willingness to share.

  • \$\begingroup\$ Just a note: pin 1 is DCD (Data Carrier Detect), not CTS (Clear to Send), which is pin 8, although you should be able to check either from software. [Pin 4 is DTR (Data Terminal Ready), which rises from between -3 V and -15 V to between +3 and +15 V when your program opens the RS-232 port.] See the "DE-9" column of en.wikipedia.org/wiki/Serial_port#Pinouts and en.wikipedia.org/wiki/RS-232. \$\endgroup\$ – PleaseStand Jul 14 '12 at 6:07

You need one of these:

enter image description here

This is the female socket which goes with the connector, it has solder pins. If you would want one for PCB mounting it would look like this:

enter image description here

Note that due to the pin spacing it isn't fit for breadboard mounting.

  • \$\begingroup\$ Thank you! I'm guessing the wire would be pretty standard but can you recommend some wiring for this particular task? (link?) \$\endgroup\$ – stormist Jul 14 '12 at 6:13
  • 1
    \$\begingroup\$ @stormist - I would use stranded wire rather than solid since they're more flexible. This wire is 26 AWG, overall diameter 1.3 mm. Since you're working with low voltage and low current neither the wire diameter nor insulation thickness is critical. IIRC the solder pins will accept wire to more than a mm thick. \$\endgroup\$ – stevenvh Jul 14 '12 at 6:27
  • \$\begingroup\$ Do you see any problems with this wire: amazon.com/100-Stranded-Wire-Gauge-Black/dp/B0006O94DE/… Thanks for your reply \$\endgroup\$ – stormist Jul 14 '12 at 6:50
  • \$\begingroup\$ @stormist - No, but then it doesn't give you much information. Should be alright, though. \$\endgroup\$ – stevenvh Jul 14 '12 at 7:07

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