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Circuits designed by David Johnson, P.E.
Last Updated on: Thursday, April 07, 2016 02:04 PM

Master Category List - Dave's Circuits

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Gadget Circuits
Dave's Gadget Circuits, Page 1, Page 2, Page 3

120 VAC Touch Switch  -  This is a capacitance based touch on/touch off switch, which can control power to a 200 watt 120vac load . . . [Circuit by David A. Johnson P.E.,  07/11/06]


14v LED AuxiliaryLamp with a 60 Watt Lamp  -  This circuit controls power to a standard 60 watt lamp plus generates an auxiliary 14v DC supply which can power an automotive style 12 LED array . . . [Hobby Circuit designed by David A. Johnson P.E.,  07/09/06]

 

1Khz to Over 70Mhz Light Receiver  -  This circuit uses one tiny C-MOS inverter IC to form a modulated light receiver with a very fast response. It is designed around a PIN photo diode that is packaged for use with plastic optical fibers. It can be used as an optical fiber receiver. By using the open end of the optical fiber it can "sniff" out any modulated light signals . . . [Hobby Circuit designed by David A. Johnson P.E.,  06/11/00]

1us LED Pulse Driver + Voltage to Frequency Converter  -  This circuit receives the signal from the above Amplifier and launches powerful 1uS infrared light pulses from a low cost LED that are frequency modulated by the audio information. The 10KHz center frequency of the pulse stream is low enough so a standard . . . [Hobby Circuit designed by David A. Johnson P.E.,  03/22/99]


1W White LED Night Light  -  As many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components.  This circuit is yet another version, which produces much more light than those other designs. . . . [Hobby Circuit designed by David A. Johnson P.E.,  11/06/08]


4-20ma Current Loop Tester  -  This circuit injects an adjustable current through a wire loop.  Using a digital current meter, the current can be adjusted from near zero to over 24 milliamps . . . [Circuit by David A. Johnson P.E.,  05/01/12]


60 Watt Lamp With Auxiliary 14v LED Lamp  -  This circuit controls power to a standard 60 watt lamp plus generates an auxiliary 14v DC supply which can power an automotive style 12 LED array . . . [Circuit by David A. Johnson P.E.,  07/09/06]


6v NMH/NiCd Battery Tester  -  I designed this circuit to test rechargeable six volt battery packs under constant current conditions.  As designed, the circuit applies a 10 Amp load to the battery pack.  A heat sink must be used on the main power transistor . . . [Circuit by David Johnson P.E.,  12/12/04]


AC Current Controls Hour Meter  -  Many systems require routine maintenance based on machine operation time.  The circuit below is a simple way to turn on a hour meter whenever AC power is supplied to the machine.  An inexpensive snap-on current transformer from Magnetics Inc, is used to . . . [Circuit by David Johnson P.E.,  02/13/10]


Automotive Electrical Voltage Indicator  -  This circuit will indicate if an automotive electrical circuit has zero volts or 12 volts present.  . . . [Circuit by David A. Johnson P.E.,  07/09/06]


Basement Doorbell Beeper  -  If you can't hear your doorbell when you are in your basement try this circuit. This circuit takes advantage of the 24vac power source located near the furnace. Using a simple current transformer technique, the circuit sounds a beeper whenever the . . . [Circuit by David Johnson P.E.,  06/04/00]


Basement Remote Doorbell  -  This circuit will activate a beeper alarm whenever the AC line voltage is less than 100vac . . . [Hobby Circuit designed by David Johnson P.E.,  07/11/06]


Dave's Gadget Circuits, Page 1, Page 2, Page 3

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