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Last Updated on: Thursday, April 07, 2016 01:02 PM

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Opto-Isolator / Opto Coupler Circuits

  • Battery Isolator:  This circuit uses a few p-channel power FETs and a new IC from Linear Technology.  It allows an alternator to charge two different lead-acid batteries but isolates the individual battery loads, so that loads on one battery do not draw power from the other battery.  This configuration is often used on recreational vehicles.  It is rated at 28v and up to 50 Amps
  • Fully Isolated 50/60Hz Sync Generator
    This circuit will produce a single pulse at the zero voltage cross points of the power line voltage.  An opto-coupler provides a very safe 5KV isolation.
  • HONEYBEE COUNTER
    I designed a circuit similar to this one a long time ago to help a beekeeper count the number of bees going into or out of a hive. The low power circuit uses a slotted opto-sensor to detect the passing bees. The circuit advances an electronic counting module whenever a honeybee passes through the sensor. The device only counts the number of bees going through the sensor. A different circuit would be needed to count the number of bees only going out or only coming into the hive.
  • MACHINE POWER LOSS BEEPER
    For some medical equipment it is important for an operator when power is lost to the machine. The beeper is powered from a 9v battery and requires the machine to have a power switch with a third set of contacts.
  • SQUARE WAVE DRIVER HAS FLEXIBLE OUTPUTS
    This circuit can produce an output signal ranging from DC to 100KHz. It can source a voltage ranging from 1v to 30v. It can sink a voltage ranging from zero volts to 30v. It can drive up to 200ma of current and can even be switched to a floating tristate output.

  • TIME TO DUST INDICATOR
    I thought about this circuit when I heard that a lot cleaning personal in hotels were either dusting rooms more often than necessary or not enough. I have not yet built and tested this circuit completely but in concept it should work. The circuit draws very low current from a +3v battery and could be housed in a package similar to a small ashtray. The assembly might be placed in a suitable out of the way area to collect dust. It would alert a maid when it was time to dust the room. The circuit detects dust with an infrared LED that is pulsed so its light shines onto a smooth flat plate. Any dust settling onto the surface is detected by a phototransistor, mounted at a 90-degree angle from the LED. When the dust reaches a particular level, sufficient light is reflected into the phototransistor to change the logic state of the circuit to an alarm condition. The alarm output could be connected to a beeper, a flashing LED or to one of the LED flashing circuits in this hobby circuit section.

Opto-Isolator / Opto Coupler Circuits

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