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• ISOLATED AC CURRENT MONITOR
  This circuit uses a small AC current transformer from Magnetek to produce an isolated voltage proportional to the AC current in the primary winding.  The transformer contains a single turn primary with a low 0.001-ohm resistance.  It can easily handle 30 amps of AC current and provides at least 500vac of isolation.  With the components shown, the output AC voltage is scaled so 1 amp of current produces 100mv of AC voltage.

• Run Switching Type AC Power Adapters on DC 
  I have received a couple emails from people looking for inexpensive DC to DC converters, which can convert 40v to 60v DC into say +5 or +12v.  Such input voltages are often found in new automotive and industrial applications with a typical DC voltage of 48 volts. It turns out that many, not all, but many, standard AC line operated power adapters, which use switch mode techniques, will indeed work great when supplied with DC instead of AC. The unit below works down to about 30v DC and delivers 500ma at 5v. If you draw less current, it will operate at even lower DC input voltages....

• VARIABLE ISOLATED AC VOLTAGE SPANS 0VAC TO 280VAC
  I designed and built this circuit about 25 years ago. It came in handy for many projects that were powered from 120 VAC, 240 VAC and 277 VAC. It provides complete isolation from the power line. It uses two 1:1 isolation transformers that are wired in parallel for the140vac range and in series for the 280vac range. The selector switch also diverts power to the appropriate output socket to avoid mishaps in sending the wrong voltage to the load. My home-built unit also included an AC volt and amp meter to monitor the output. However, this circuit only indicates the AC power connections.