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Last Updated: November 22, 2021 03:00 PM
Circuits Designed by Dave Johnson, P.E. :
Reflected Infrared Light Switch -  infrared light reflected off a finger is used to activate this switch circuit.  Drawing only 30uA from a 3v supply, this circuit will detect a human finger with a range of about 1 inch.  The sensor uses an inexpensive infrared LED and a matching photo diode . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Replace a Pushbutton Switch with this Infrared Safety Switch -  Using a slotted optical sensor, this circuit can be used as a replacement for a large mushroom pushbutton safety switch . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-778-8407




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

RC Receiver Hosts Two Independent Switches -  06/06/96  EDN Design Ideas:  Typical inexpensive radio-control (RC] systems have servo-motor outputs, but no on/off switch outputs.  You can add two independent RC switches to a system without making any transmitter or receiver modifications Design by Tom Howell, US Army ARDEC, Picatinny Arsenal, Dover, NJ

Read multiple switches using ADC -  EDN Design Ideas:  06/29/2015    How the author learned to interface 8 switches using zero GPiOs Design by Les Hughson

Receiver-Ultrasonic Switch -  The circuit described generates (transmits) ultrasonic sound of frequency between 40 and 50 kHz.  As with any other remote control system this cirucit comprises of a minI transmitter and a receiver circuit.  Transmitter generates ultrasonic sound and the receiver senses ultrasonic sound from the transmitter and switches on a relay __ Designed by Andy Wilson

Reducing Relay Power Consumption -  Relays are often used as electrically controlled switches.  Unlike transistors, their switch contacts are electrically isolated from the control input.  On the other hand, the power dissipation in a relay coil may be unattractive for battery-operated applications.  Adding an analogue switch lowers the dissipation, allowing the relay to operate at a lower voltage.  The circuit__ 

Reed Switches -  Find out more about reed switches and their uses in RE.   __ Designed by REUK-Renewable Energy UK website

Reflected Infrared Light Switch -  infrared light reflected off a finger is used to activate this switch circuit.  Drawing only 30uA from a 3v supply, this circuit will detect a human finger with a range of about 1 inch.  The sensor uses an inexpensive infrared LED and a matching photo diode . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Relay Coil Energy Saver -  Some relays will become warm if they remain energized for some time.  The circuit shown here will actuate the relay as before but then reduce the ‘hold’ current through the relay coil current by about 50%, thus considerably reducing the amount of heat dissipation and wasted power.  The circuit is only suitable for relays that__ 

Relay driver saves substantial power -  EDN Design Ideas:  July 2, 1998        NOTE:    FILE
has multiple design, scroll for this one.  it is common practice to operate relays and solenoids at a reduced holding power once the mechanical actuation takes place.  Relays are usually specified to pull in within 3 msec at 80% of the rated voltage and to release at 30% of the rated voltage.  The circuit in Figure 1 drives as many as eight 12V (Ž120V coil) power relays, which memory-map into an 8-bit mP bus.  An octal latch stores the relay status, where each bit of the 8-bit word serves a separate relay (0=off, 1=on).  The latch's Select line latches data on the rising edge.  Whenever the relay's status data changes, the relay's drive voltage rises to the full 12V for 140 msec to ensure that the relay pulls in.  A series zener diode then reduces the relay's drive voltage by 50% to reduce dissipation. Design by Tim Herklots, Maxim Integrated Products, Southamption, UK

Relay Driver Switches Two Relays with One Pin -  03/03/11  EDN Design Ideas:  Logic 1, logic 0, and high-Z make for three possible states: forward, reverse, and off. Design by Gunther Kraut, PhD, Egmating, Germany

Relay Toggle Switch -  I designed this relay circuit to function as a DPDT toggle which is controlled by a momentary switch.  I strive to keep my circuits simple with little or no integration (555’s, transistors, etc).  The circuit is shown active or “on” mode.  Half of RL1 and RL2 manipulate the switching and the other is connected to__ 

Relay Toggle using a 555 Timer -  This is probably the best toggle circuit.   __ Designed by Bill Bowden

Relay Toggle using a MOSFET  & Push Button -  This circuit is similar to the one above, but uses a N channel mosfet such as iRF530, 540, 640, etc.  in place of the NPN transistor.  Smaller mosfets could be used, but I don't know the part numbers.  I tested the circuit with a iRF640, iRFZ44, iRFZ34 and REP50N06.   The circuit has the same three advantages, it requires only a few parts, always comes up with the relay deactivated, and doesn't need any switch debouncing. __ Designed by Bill Bowden

Remote Control Encoder/Decoder with PIC16C620 & PIC12C508 -  Control up to 8 devices by this easy constructable remote control.  it can work as a radio or infrared remote control, depending on the components.  Each device output can be configured to be momentary (turned on while you press the button) or latched.  Latched outputs can be toggled on/off by one button per channel, or turned on and off by two buttons per channel.   __ Designed by Peter Jakab

Remote control turns battery on & off -  09/12/97 EDN Design Ideas:  The circuit in Figure 1 acts as a latching solid-state relay.  A short application of a magnetic field in the vicinity of S1 toggles the relay on and off.  The relay switches power from a 3V battery at load currents as high as 10 mA.  This remote switch is ideal for battery-powered applications.  in the off state, the circuit draws no current; in the on state, the circuit draws only 100 µA.  All the parts are inexpensive and readily available.    Design by Allen Harstine,Integrated Measurement Systems Inc, Beaverton, OR

Remote Doorbell Warning Switch -  This circuit should only be used with the solenoid type chime doorbells, the electronic type that play tunes will not work here.  The hardest part for this circuit was the title.  it is quite easy to miss the sound of a doorbell if you are watching TV , this circuit gets round the problem by providing a visual indication, i.  e.  a lamp __ Designed by Andy Collison

Remote Infrared Terminal -  This unit provide 2 way IR communications using a numeric keypad and an LCD display.  Data is sent and recieved in acsiI with no regard to what the data means to any particular device __ Designed by Luhan Monat - Mesa Arizona

Remote Selection Video Switch For Security Surveillance System -  A video switcher (also called vision mixer, video mixer, or production switcher) is a device used to select between several different video sources and in some cases composing video sources together to create special effects.  This is similar to what a mixing console does for audio.  The A/B Switch circuit consists of three ICs  and__ 

Remote Switch Uses No-Power Fiber-Optic Link -  10/10/96 EDN Design Ideas:  The heavy-duty switching device in Figure 1 counts the number of products manufactured and rolled out of a production line per hour.  The switch is useful for counting rolling heavy objects or materials weighing one to several thousand kilograms.  it generates one pulse per Design by Shyam Tiwari, IGKAR, Kalpakkam, India

Replace a Pushbutton Switch with this Infrared Safety Switch -  Using a slotted optical sensor, this circuit can be used as a replacement for a large mushroom pushbutton safety switch . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Replace a rotary switch with a potentiometer -  EDN Design Ideas:  04/07/2014     Why use an expensive rotary switch with your microcontroller when you can use a cheap pot instead? Design by Claude Haridge

RF SPDT switch IC takes you to 3 GHz -  EDN-Design ideas -- 04/23/2004    The PE4259 from Peregrine Semiconductor gives you SPDT switching from dc to 3 GHz, along with requisite control logic and a low-voltage interface. Design by Bill Schweber

RS232 DB-9 Switch -  Simple hardware expands COM1 to COM1/1 and COM1/2;  RS232 DB-9 Switch to Flip Between Two Serial Ports __ Designed by Wichit Sirichote

RS-232C port scans remote keypad -  12/04/97 EDN Design Ideas:  in many embedded or control applications, you might prefer to use a small, customized keypad with your PC-based system rather than a full-fledged alphanumeric keyboard.  You may also need to locate the keypad some distance from the system hardware.  if you have Design by SK Shenoy, NPOL, Kochi, India

RS232C Powers & Reads 8 Bit Switch Matrix -  04/11/96 EDN Design Ideas:  The circuit in Figure 1 provide as a remote menu-selection switch matrix for PCs.  it connects a linear, 8-bit switch to the RS-232C port; the RS-232C signal pins provide the circuit's frugal power requirements.  You can easily modify the circuit for moreswitch inputs.  The heart of the circuit is a 74HC165 8-bit, serial-output shift register.  it's important that you use either this register or a similar one from a low-power IC family.  The shift register has eight parallel-input pins that receive their drive from an 8-bit DiP-switch matrix.   Design by BR Dhananjay Gadre, IUCAA, Pune, India

Got Designs?
Please eMail
if you want me to link to and/or post your original design Thanks.

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