Simple DC power delay circuit

jacky May 25, 2010 7 Comments
Description. The circuit diagram shown here is of a simple DC power delay circuit that is based on an SCR. This circuit is a very handy one and can be employed in many applications. The working of this circuit is very simple. When the input power is applied the capacitor C2 charges through resistor R2 and when the voltage across the capacitor just exceeds the Zener diode D3’s breakdown voltage, it breaks down and the SCR H1 is triggered...
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Fuse with status indicator.

john August 4, 2009 2 Comments
Description. Here is the circuit diagram of a fuse that has an automatic status indicator. This circuit can be added to circuit that operates from 12V DC. As long as the fuse is intact, the LED D3 will glow continuously and when the fuse blows off the LED will start and continue blinking. The first part of the circuit includes an astable multivibrator built around transistors Q1 and Q2.The output of the multivibrator is coupled to the base of...
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Temperature controlled fan regulator

john December 9, 2018 34 Comments
How cool will it be to have an intelligent ceiling fan that will auto-adjust its speed to your comfort! That’s what we are trying to achieve here. Fans help to reduce room temperature by circulating air. This circulation mixes hot and cool air in the room, and in effect reduces the temperature to an average value of the hot and cool air temperatures. As you know, we need some input to control the speed of the fan. Here temperature is...
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Brightness controller for low power lamps.

admin November 16, 2011 6 Comments
Description. The circuit given here can be used to control the brightness of low power incandescent lamps. The circuit is based on IC NE555 which is wired as an astable multivibrator with variable duty cycle. The output of IC is connected to the base of transistor Q1.The Q1 drives the lamp. The duty cycle of the multivibrator can be varied by varying the POT R4.As a result, the brightness of the lamp varies according to the position of the...
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Temperature controlled DC fan

admin August 30, 2008 10 Comments
Description. Here is a simple circuit based on two transistors that can be used to control the speed of a 12 V DC fan depending on the temperature.A thermistor (R1) is used to sense the temperature. When the temperature increases the base current of Q1 (BC 547) increases which in turn decreases the collector voltage of the same transistor. Since the collector of Q1 is coupled to the base of Q2 (BD 140), the decrease in collector voltage of...
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Modified lamp dimmer circuit

admin January 24, 2012 18 Comments
Description. This is a modification of the circuit Simple Lamp Dimmer/Fan Regulator  previously  posted here. The working of the circuit is same as that of the previous, but in addition a snubber circuit consisting of resistor R4 and capacitor C3  is included to improve the performance of the triac T1. A fuse is also included for better safety. I think this is the better circuit to try . Circuit diagram with Parts list . Notes. No matter how  what...
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PWM Motor Speed Control Circuit

admin October 30, 2018 17 Comments
In this project guide we’re building PWM Motor Speed Control circuit using two digital IC’s. We’ve published different types of PWM circuits, say from the basic PWM using NE 555 IC, to the much advanced PWM using micro controllers like AVR, 8051, and Arduino boards. PWM – is basically pulse width modulation and if you’re new to this – please go through our basic guides – Pulse width modulation  and other PWM articles. Description Here is a simple PWM motor...
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Simple Lamp Dimmer/ Fan Regulator Circuit

admin November 3, 2018 34 Comments
Lamp Dimmer/Fan Regulator Circuit We have modified this circuit: - Take a look - Modified Lamp Dimmer Description The light dimmer circuit or fan regulator circuit (either case, the circuit and design are the same, only difference is the output load to be varied, that is, fan or light) is used to control the brightness of the light or the speed of the fan according to our desire. The objective of the circuit is to vary in intensity the...
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