kolderman wrote:I want to wire a on/off toggle switch onto a jumper (actually the address selector jumper on the PCMIDI card). I suppose it applies to any other jumper you want to be able to easily open/close.
I have attached a photo of an example switch.
There are three connectors obviously....do I connect 2 of them to the jumper wires, and the third to ground? Is it clear which is which?
You first need to identify which of the three terminals is "common" - two methods here:
1) Look at the switch and look for a terminal marked "COM" or "C"
2) Use a continuity tester/buzzer/bleeper or a multimeter. Put one probe on the centre pin, and another on the left pin. If you don't get a beep, operate the switch. If you still don't get a beep, then the pin you weren't probing is common. If you do get a beep, operate the switch and move one of the probes to the other pin. If it beeps, the probe you didn't move is on the common pin.
Secondly, look at your jumper header.
If it has two pins (i.e. the jumper is "ON" or "OFF"), connect the common terminal on the switch to one pin, and one of the other terminals on the switch to the other pin. Leave the third pin on the switch unconnected (and put some insulating tape on it).
If the header has three pins, and has two positions (for example 3 pins labelled 1,2 and 3, and the link is set to 1-2 or 2-3), connect the common terminal on the switch to the central pin.
Connect the two other pins to the outer pins of the set of three (for example for 3 pins labelled 1,2 and 3, connect the common terminal to 2, and the other terminals to 1 and 3).
You might want to consider using pre-terminated jumper wires to connect to the PCB headers - search for "female jumper wires" or "male to female jumper wires".
The no-nos are:
a) Do not connect unused switch pins to ground.
b) Unless you know what you are doing, do not use a SPDT switch (with three terminals) to replace a two position jumper which uses four pins (for example, 4 pins labelled "Link 1 and Link 2" of which you fit one link, but not both, or 4 pins labelled 1,2,3,4 and you fit 1-2 or 3-4, but not both) (Hint: use a DPDT switch (six terminals), and wire each pole to a separate pair).