Low cost fire alarm circuit.

admin January 21, 2014 89 Comments
Description. When there is a fire breakout in the room the temperature increases. This ultra compact and low cost fire alarm senses fire breakout based on this fact. Transistor BC177 (Q1) is used as the fire sensor here. When the temperature increases the leakage current of this transistor also increases. The circuit is designed so that when there is an increase in the leakage current of Q1, transistor Q2 will get biased. As a result when there is a...
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Liquid Level Switch

admin October 30, 2018 9 Comments
In this guide, we are designing a Liquid Level Switch using 3 transistors (BC107), some passive components, a diode and a couple of relays. This is basically a level sensing circuit designed using minimal components. If you’re looking for an efficient level sensing circuit, you would be better off with our water level controller circuit. Description Here is a simple level switch circuit that switches on one relay and switches off another relay when the fluid level exceeds the...
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Touch Switch Circuit

admin October 30, 2018 33 Comments
In this project guide, we’re building a Touch Switch Circuit using NE 555 IC. As you know, NE/SE 555 is a very popular timer IC with multiple applications in different projects. A touch switch is basically a simple switching circuit activated upon a touch. If you’re new to 555 IC, please take time to read our beginners guide on 555 IC. Also, you can try many of our applications using 555 timer IC Description This is the circuit diagram...
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Photo Switch Circuit

admin October 30, 2018 16 Comments
In this project, We’re building a Photo Switch Circuit using 555 IC. If you’re not familiar with term ‘photo switch’ – this is nothing but a light activated switch. The switch will turn ON/OFF based on light intensity. We’ve designed this photo switch circuit using simple & popular components. The heart of this circuit is the very popular NE/SE 555 IC – which is a timer IC almost everyone is familiar with. If you’re new to 555 IC, you...
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InfraRed (IR) Sensor/Detector Circuit

jacky November 6, 2018 11 Comments
InfraRed (IR) Sensor/Detector Circuit Description The IR circuit described below is mainly designed for liquid level detection or proximity detection. The IR sensors used here are an IR LED and an IR photo diode. The circuit operates by detecting the distance from the target by reflection of an infrared beam. The biggest advantage of this circuit is that there is no physical contact with the liquid whose level is to be measured. Such a circuit needs to be installed only...
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