Tag Archives: Relay

Sound-Activated Lamp (Relay Switch)

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This simple circuit shown int the schematic diagram actives the switch using sound. We can use this circuit for various applications, such as automatic (sound-controlled) disco light or car’s LED light show. The Q1 amplify the audio from mic. The R1 is used to adjust the peak of signal to… Read more »

Circuit Project: Sound Activated Switch II

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With this sound activated switch, control by sound may be very useful, not just on a robot but also for a bit of home automation, for example a sound-activated light responding to a knock on the door or a hand clap. The light will be automatically switched off after a… Read more »

Relay Toggle Switch

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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… Read more »

Fuse Saver

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This circuit will be particularly useful to those hobbyists who use a ‘breadboard’ to try out ideas and who also use a simple ‘home-made’ DC power supply consisting of a transformer, rectifier, smoothing capacitor and protective fuse, that is, one without over current protection! In this circuit, the detecting element… Read more »

Electronic Fuse Employs A Relay

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While many power supplies can be set to limit their output current to a defined level, to protect the circuit they are powering, no such protection is available if you are powering a circuit from a battery. If a fault develops, the circuit can blow before you have a chance… Read more »

Multi-Position Mains Switch

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The circuit shown here was born out of necessity after one of our colleagues had just renovated his kitchen and realized afterwards that there were not enough switches. Obviously he was not too keen to partially demolish the kitchen to install a few additional wires in the already tiled wall…. Read more »

Mains Remote Switch

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This compact design forms a remotely operated switch that receives its control signal via the mains voltage. The switch is operated using the ‘mains remote transmitter’ described elsewhere in this issue. With this transmitter, a switch should be connected between pins 1 and 2 of K1. Depending on the application,… Read more »

Intelligent Electronic Lock

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This intelligent electronic lock circuit is built using transistors only. To open this electronic lock, one has to press tactile switches S1 through S4 sequentially. For deception you may annotate these switches with different numbers on the control panel/keypad. For example, if you want to use ten switches on the… Read more »

Clap Sensitive On-Off Relay

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3V Battery operated, Small portable unit This circuit was intended to activate a relay by means of a hand clap. Further claps will turn-off the relay. An interesting and unusual feature of this project is the 3V battery operation. The circuit’s sensitivity was deliberately reduced, in order to avoid unpredictable… Read more »

SMPSU With A Relay

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Switched mode power supply units (SMPSUs) are popular but difficult to build oneself as well problematic when it comes to understanding their design principles. Building your own SMPSU typically requires a lot of expertise, hard to find components and time. The circuit shown here is educational only and devised to… Read more »