Tips on Using the Power Supplies

Pay attention!!  This could save you a lot of time!!

The bench Power Supplies are industrial-strength instruments that are sold for big bucks, but partially donated to UW so we can use them in our courses.  Used in the right way, they are very powerful and productive.  However, the supplies have certain quirks that can make them difficult to use at times and which, if ignored, can lead to frustration.  Fortunately, some of these problems can be avoided by following a few simple guidelines and knowing where the possible problems lie.  On this page we will attempt to point out these problems, and where possible, give some ideas for avoiding or fixing them.  If you come up with new tips, please mail them to us and we will add them to this list.  By the way, this page is written on the assumption that you will follow our advice.  Specifically, we don't talk about what to do with all the bad things that happen if you don't.
 

General Tips:

• Keep it simple and don't stray from straightforward, proven ways of doing things.  Don't expect the tools to do things the way you think they should be done.  Don't fight the tools, go with the flow.  The tools always win.
• When wiring up a new circuit, you should always double- and triple-check your wiring before applying power.  It also helps to have someone else look it over as well (your lab partner works well).  If you don't understand something, don't just guess and hope that it will work - find someone who can help so that you don't end up damaging your circuitry.  An even better solution when wiring up a new circuit is to power up without any chips the first time; you can then use a multimeter to check your power and ground connections at each chip socket.

Grounding:

• If you use more than one power supply in a system, you must connect the grounds from separate supplies together.  If you don't do this, the voltage difference between signals shared by the circuits can be very large - more than enough to damage components.

Current Limiting:

• Each supply has a control to limit it's output current.  This is intended to protect connected hardware in the event of a fault, however if set to low for normal operation it will have the effect of reducing the output voltage perhaps below where the hardware will operate correctly.  The current limit should be properly set to supply enough current for normal operation with some reasonable (but not excessive so as to afford protection) margin to spare.  To do this, start with the load disconnected, the current limit set high and adjust the no-load output voltage as required; then connect the load and reduce the current limit to where the output voltage just begins to fall, then increase the limit for an appropriate margin.