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

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More Automotive Circuits
 

125khz Wireless Smart Key Detector  -  This circuit will turn on an indicator light whenever it detects a smart car key containing an RFID chip . . . [Circuit by David A. Johnson P.E.,  07/12/06]


12v DC Motor with Logic Controlled Automatic Brake  -  There are times when you would like to control a DC motor using a simple +5v logic swing signal.  The circuit below performs this feat and also includes an automatic motor braking circuit.  When the input logic signal swings from 0v to +5v, the n-channel . . . [Hobby Circuit designed by Dave Johnson P.E.,  02/18/10]

Alarm Beeps when the “Check Engine” Light Turns On  -  When wired into a car’s indicator light panel, this circuit will turn on a loud beeper when the “check engine” light turns on . . . [Circuit by Dave Johnson P.E.,  07/09/06]


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]


Auxiliary 12v Automotive Style LED Light Makes Table Lamp  -  This circuit provides about one watt of non-isolated DC power for an automotive type 12v LED array lamp in addition to a standard incandescent table lamp . . . [Hobby Circuit designed by David A. Johnson P.E.,  07/09/06]


Beeper indicats Check Engine  -  When driving down a busy road, you may not notice a “check engine” indicator light that suddenly turns on within the car’s instrument panel.  You could drive for many miles before noticing the light.  To provide an audible indication of trouble, the hobby . . . [Hobby Circuit designed by David A. Johnson P.E.,  07/09/06]


Car Ignition 12v Switch  -  A Discover Circuits visitor needed a way to redirect +12v DC in his car to some auxiliary loads whenever the car’s engine was running.  Many cars have cigarette lighter outlet jacks, which are either live all the time or become live when the car’s engine is running . . . [Hobby Circuit designed by Dave Johnson P.E.,  02/26/12]


Check Engine Beeper  -  When driving down a busy road, you may not notice a “check engine” indicator light that suddenly turns on within the car’s instrument panel.  You could drive for many miles before noticing the light.  To provide an audible indication of trouble, the hobby . . . [Hobby Circuit designed by David Johnson P.E.,  07/09/06]


Fake Car Alarm Light  -  Whenever the car’s ignition is turned off, this circuit activates a flashing LED, which can be positioned to appear as an active alarm system . . . [Circuit by Dave Johnson P.E.,  10/16/05]


Flashing Light to simulate Car Alarm  -  Whenever the car’s ignition is turned off, this circuit activates a flashing LED, which can be positioned to appear as an active alarm system . . . [Hobby Circuit designed by David Johnson P.E.,  10/16/05]


Indicates Automotive Electrical Voltage  -  When troubleshooting the 12v electrical system of an automobile, it is nice to have a simple voltage indicator tool instead of a voltmeter.  This electronic circuit, hobby circuit is powered by two AA or even two N cells, which will provide enough energy . . . [Hobby Circuit designed by Dave Johnson P.E.,  07/09/06]


Logic Controlled 12v DC Motor With Automatic Brake  -  There are times when you would like to control a DC motor using a simple +5v logic swing signal.  The circuit below performs this feat and also includes an automatic motor braking circuit.  This circuit will bring a fast moving DC motor to a stop in seconds.  The braking action is automatically applied whenever DC power is removed . . . [Circuit by David Johnson P.E.,  02/18/10]


RFID Smart Key Detector  -  The hobby circuit below was designed to indicate if a key held over the small coil of wire contains a 125KHz RFID chip. These chips are often used in smart car ignition keys.  The left side circuit forms a 125KHz power oscillator, which drives the 680uH a . . . [Hobby Circuit designed by David A. Johnson P.E.,  07/09/06]


Table Lamp With Auxiliary 12v Automotive Style LED Light  -  This circuit provides about one watt of non-isolated DC power for an automotive type 12v LED array lamp in addition to a standard incandescent table lamp . . . [Circuit by Dave Johnson P.E.,  07/09/06]


Wireless RFID Smart Key Detector  -  Many cars now use a key with an imbedded RFID microchip.  The microchip is read when the key is inserted into the car’s ignition.  The keys containing a microchip often look the same as most other keys. People duplicating car keys will often not know of the microchip.  This circuit will light a LED if it detects a key containing a 125KHz RFID chip. . . . [Hobby Circuit designed by Dave Johnson P.E.,  07/09/06]

More Automotive Circuits

Master Category List - Dave's Circuits


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