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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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Door Bell Circuits

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 Dave 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 A. Johnson P.E.,  07/11/06]


Door Knob Alarm  -  Many companies offer simple alarm devices for personal use in bedrooms or hotel rooms. A metal chain attached to a box holding the electronics is placed around the inside doorknob of a wood door. Anyone grabbing the knob from the outside is detected . . . [Circuit by David Johnson P.E.,  05/29/00]

Door Knock Beeper  -  In some apartment buildings and homes, not equipped with a door bell, it may be hard to hear someone knocking on the front door.  The circuit below provides a means to activate a loud beeping sound inside, whenever someone knocks on the door . . . [Circuit by Dave Johnson P.E.,  06/14/09]


Doorbell heard in Basement  -  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 . . . [Hobby Circuit designed by Dave Johnson P.E.,  06/04/00]


Illuminated 16vac Doorbell Lamp Replacement    -  A while back I noticed that the lamp inside the illuminated pushbutton switch for my doorbell burned out.  I carefully removed the doorbell, opened the switch housing and then replaced the incandescent lamp inside with the circuit shown below.  The circuit uses two small but very bright green LEDs from King Bright.  The resistor sets the average LED current at about 3ma. The diode prevents reverse biasing the LEDs.  The two lamps emit plenty of light and should last much longer than the incandescent lamp they replaced . . . [Hobby Circuit designed by Dave Johnson P.E.,  10/22/06]


Knocking rings Doorbell  -  In some apartment buildings and homes, not equipped with a door bell, it may be hard to hear someone knocking on the front door.  The circuit below provides a means to activate a loud beeping sound inside, whenever someone knocks on the door . . . [Hobby Circuit designed by David A. Johnson P.E.,  06/14/09]


Next-Generation-Star-Trek Doorbell  -  In the Star Trek “Next Generation” TV series, the doorbell outside the private quarters of a crew member makes a particular “beep-boop” sound.  The 3v battery powered circuit below tries to simulate this sound. The circuit uses one 74HCT74 dual D flip/flop . . . [Hobby Circuit designed by Dave Johnson P.E.,  10/12/01]


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


Star Trek Doorbell  -  In the Star Trek “Next Generation” TV series, the doorbell outside the private quarters of a crew member makes a particular “beep-boop” sound.  The 3v battery powered circuit below tries to simulate this sound. The circuit uses one 74HCT74 dual D flip/flop . . . [Circuit by David A. Johnson P.E.,  10/12/01]


Star-Trek Next-Generation Doorbell  -  In the Star Trek “Next Generation” TV series, the doorbell outside the private quarters of a crew member makes a particular “beep-boop” sound.  The 3v battery powered circuit below tries to simulate this sound. The circuit uses one 74HCT74 dual D flip/flop . . . [Hobby Circuit designed by David A. Johnson P.E.,  10/12/01]


Touch Alarm for Door Knob  -  I designed this hobby circuit many years ago and it seems be a very popular construction project.  Many companies offer simple alarm devices for personal use in bedrooms or hotel rooms. A metal chain attached to a box holding the electronics is place . . . [Hobby Circuit designed by David A. Johnson P.E.,  05/29/00]

 

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