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Gadget Circuits
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Last Updated on:
Wednesday, August 19, 2015 05:38 AM


Circuits Designed by Dave Johnson, P.E. :
  • 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]

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

10 Channel Light Controller -  A 10 channel light controller using PWM/ up to 1a per channel at 12v. . .  [by P. Townshend - EduTek Ltd]

 

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]

 

2-wire Game Show Time -  Several Game Show timers included, scroll to find this one. The game show timer determines which contestant presses their button first by lighting a lamp and ringing a bell and the slower  contestants are locked out. The circuit is convenient in that only two wires are needed to interconnect the stations and the wires may all go back to the base unit or they may be "daisy-chained" between stations. There is no electronic limit on the number of stations. The circuit uses a 24 volt power source and 12 volt lamps when built as shown but the experienced experimenter may scale these voltages along with the zener voltages if desired. If the SCR triggers when the power is applied or when the reset button is pressed, add a 0. 1uF capacitor from anode to cathode. (A sudden increase in voltage across some SCRs can trigger them, especially if the gate impedance is high. ) . . .  [Charles Wenzel (unless otherwise noted)]

 

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]

 

5-Finger LED Counter -  Our FIVER - P5 has many applications; Teach your children how to count to five! Draw attention and a smile. Press the push button five times and trigger your hobby rocket, etc. The unique small design will allow you to mount it almost anywhere. Operate it with 9V battery, 12V car battery, four 1. 5V batteries, or via one of our battery simulator kits. The alternative uses are endless. . . .  [Kit from Elich Industrial Development, Corp]

 

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]

 

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Gadget Circuits
Gadgets:  # - C       D - E      F - L      M - N      O - S      T - Z


HOME Schematics Index Hobby Corner Dave's Circuits Electronic Resources Contact Info
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