How To Wire Polarity Switch On Test Rig?

[whitebread47]

Hi folks, I'm new here but active on similar fora.  To lighten the load of questions I pose to people in those places, I have come here with a question.

I have built a basic testing rig w/ a DC jack for power.  I want to be able to switch between + & - ground while using the same rig to test both the usual circuits and PNP circuits.  I've been told I can use a DPDT to switch between polarities; problem is, I'm not sure how to do this and have failed to find any diagrams or figure it out.  Could someone explain to me how to do this or possibly link a diagram?

Or, could I simply wire a battery clip in reverse polarity and just test PNP pedals with the clip?

Thanks in advance for any help!

[artifus]

here ya go

[haveyouseenhim]

 

[juancra]

This setup can be useful when assembling a RG's germanium transistor tester. Mentioning this since the post solved switching grounds in my attempt to build one =)

[R O Tiree]

Make sure you clearly label the switch "Positive GND" one way and "Negative GND" the other. Before firing up a new circuit for the first time, make absolutely damn sure that you have (a) the switch in the correct place and (b) red wire to positive rail and black wire to the negative rail of your circuit under test - it's all very well having the switch in the right place, but if your bus connections are reversed...Only a few seconds with the wrong polarity will fry opamps and other ICs. Polarised caps will also be damaged (but might still work... kinda...). Diodes might or might not be fried, depending upon how much current passes and for how long.

To be honest, the best way to ensure you don't stuff this up is to just run a red wire from the positive terminal of your supply and a black one from the negative terminal and then connect them to the relevant voltage rail.