Battery Delpletion Monitor

It was required to monitor Battery level, the battery powers up the Compressor to supply oxygen to divers working under water.  Since the device will have to work under water it has to be water tight, produce enough loud sound (100db+) with special modulation.  Following were few requirements.

  1.  It will monitor battery depletion and switch on the alarm function at 11V (+/- 1%).
  2.  It will be possible to alter this threshold value of 11V in the future by simply replacing a component on the PCB (e.g. resistor) with a one with different value, i.e. we do not wish the use of trimpots and other operator-adjustable components.
  3. The switching of the alarm function will be sharp despite some voltage fluctuation as a result of the compressor operation.
  4.  No timer is required, i.e. the alarm will stay on until the battery is completely depleted or the entire device switched off by user.