Ok I'm feeling dumb right now. I got one of these momentary dpdt switches and can see via ohm meter that the middle terminals are normally connected to one of their corresponding edge terminals when the switch is "NOT pushed." However, when I push the switch, I see the connection broken on the terminal that was previously connected, but I also expect the middle terminals to be connected to the "other" set of edge terminals. However, I don't see continuity. IOW, I expect the dpdt functionality explained in this article, albeit a toggle dpdt. I want to hook this up as a "normally off" switch rather than a "normally on" switch. I do need a dpdt since I need it to control two circuits. I have used TWO different ohm meters just to make sure. What gives?

  • 1
    \$\begingroup\$ What does the datasheet say? \$\endgroup\$ Dec 30, 2015 at 2:55

1 Answer 1


There is no guarantee it will be the center terminal that is common. Just probe it out. It will almost surely be symmetric on either side, but it may be one of the end terminals that is the common for each side.

In any case, there are only two 'states' for the switch, so write down what is connected to what when the plunger is pressed and what is connected to what when the plunger is released. If there are 6 connections you need to make a total of 30 continuity tests (5 + 4 + 3 + 2 + 1 for each state) to be completely systematic about it. If you short a few together and have a good guess you can cut it down to just a few tests.

Edit: Here is a similar looking part, and the middle indeed is the common:

enter image description here

  • \$\begingroup\$ Thanks, you gave me hope. Unfortunately, the middle terminals are the only ones that exhibit an on/off continuity to the their one set of corresponding terminals. IOW, I'm pretty sure the middle terminals are common. \$\endgroup\$
    – Chris F
    Dec 30, 2015 at 3:20
  • \$\begingroup\$ WT...? From the page you provided, my theoretical expectations on the functionality is correct, just not my empirical data. Unless that's a different part (though it sure looks like the one I have). \$\endgroup\$
    – Chris F
    Dec 30, 2015 at 4:14
  • \$\begingroup\$ @ChrisF Perhaps the sample you have is defective or has been stomped to death. Or is just DPST. \$\endgroup\$ Dec 30, 2015 at 4:24
  • 2
    \$\begingroup\$ I got smart and got another sample, and this one works as expected. Ugh. I feel dumber now :) \$\endgroup\$
    – Chris F
    Dec 30, 2015 at 4:32
  • \$\begingroup\$ Mystery solved. Good show. \$\endgroup\$ Dec 30, 2015 at 4:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.