Ken says: Russell, Vishay have introduced a free thermal simulator called ThermaSim. It's designed to allow thermal analysis of systems using their power MOSFETs. I haven't looked at it yet but it occurred to me that it may be usable more generally. The excellent (and free) FEMM package can of course be used - but it has a pretty steep learning curve. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .