Breadboard power supply woes

I have been using a breadboard power supply for a while.  Over the last couple of days I have been working with some 3.3V ICs and couldn’t figure out why they were failing on me.  Somehow I was breaking them so I checked and re-checked everything I could.

While looking at my breadboard power supply … shown below … I had a horrible realization:


This is a dual voltage converter.  From a 7V-12V input, it will produce either 5V or 3.3V.  There is a switch on it which controls which voltage is delivered.  Notice that the switch is set of 3V.

Now take a careful look at both sides of the breadboard adapter.  The right side is labeled VC/GND while the other is labeled 5V/GND.

Yup … you guessed it, even with the switch set at 3V, the right hand side connectors were at 3V as desired but the left were at 5V.  In my circuits, just by chance, I had been using the right rail most of the time and hence all had been working … but in the last couple of days I have been using the left rail … and cooking my 3.3V ICs.