This circuit for very long-time intervals was found in the March 1993 Radio Electronics magazine. Times of several days or even weeks can be achieved depending on the value of C1.
Mean Well 480W HVG-480 LED drivers can be purchased from Mouser Electronics. These drivers operate with...
This circuit shuts off and locks the power to a load in the event of a failure. The circuit is from...
The small experimental transmitter of the figure can be used as a protable microphone or in...