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Circuits designed by David Johnson, P.E.
Last Updated on:
Friday, March 23, 2012 08:47 AM
Master Category List -
Dave's Circuits
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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
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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.
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- 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.
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- 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.
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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.
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Opto-Isolator /
Opto Coupler Circuits
Master Category List - Dave's Circuits
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