isolated power supplies in series -- polarity?

[andrew_k]

I want to make a Y cable to bridge two isolated 9v 200ma power supplies on my BBE supa charger to run me neovibe.

My question is, if I'm connecting power line A's negative to line B's positive and A's positive to B's negative, which way around are the two lines I run off the point at which they connect?

Here's some ascii art to demonstrate my confusion:

Code Select Expand



  A -  B+     A+    B-
  |     |     |     |
  \     /     \     /
   \   /       \   /
     |           |
     | C ?       |  C ?


[bkanber]

That's not the way you're supposed to attach power supplies in series Though I admit, once you even glance at it the wrong way, it can become very confusing and take a while to resolve.

You have two power supplies, A and B. You connect A's negative to B's positive. You leave those alone. Then you use A's positive as the overall positive, and B's negative as the overall negative.

Like so!:

A-    B+    A+    B-
|------|     |      |
               |       |
               |       |
              C+     C-


You can also do it the other way around, ie connect A+ and B-, and use A- as negative and B+ as positive.

[andrew_k]

You rock.

Thanks man!