A Simple design of PIR Light using Tranformerless Power Supply and Triac for driving the load. Too compact and can be enclosed in a small case. The light turns on when the PIR sensor detects human movement and turns off after the preset time. Re triggers in another movement. Its range is 30 cm to 10 meters and time delay, 30 seconds to 3 minutes both can be adjusted using the presets in the PIR sensor Module.
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Most simple Transformerless power supply that can convert 220 V AC to DC. Out put DC depends on the value of the Zener used. Output current is 60-80 mA.
See the step wise procedure
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The serious drawback of the Transformerless power supply is the low current at the output. So we can’t drive loads that require more than 75 mA current, mainly High watt LEDs and Relay driver circuits. As a rule, 75 mA current will be available per uF capacitance. But this is theoretical and in practical situation, it will be less than 75 mA, because of the low input voltage, quality of capacitor etc. But we can increase the output current to 400 mA or higher using this circuit. It can be used to light High power LEDs, Relay driver circuit etc. One condition is must. The circuit should be enclosed in a shock proof case without any contact point outside the case. Such circuits should not be used as External battery chargers since the output is at mains potential.
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Imagine how much electricity wastage occurs when the Electric Iron or Water heater left switched on for many hours unknowingly after the use. Don’t worry; hook up this tiny circuit in the existing Socket where the device is connected. It will flash brilliantly and reminds you to switch off the device after its use. Its cost is just Rs.10 but it saves hundreds of rupees. Probably, this is the simplest LED Flasher that operates in Mains. Check it
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We all use LED bulbs today to save energy. Different types of LED bulbs ranging from 3 Watts to 15 Watts are now available at low cost. The LED bulb has an array of serially connected 0.5 watt Chip LEDs and a small capacitor power supply. We can also easily make the LED bulb. Let us see what is inside the LED bulb and the circuit operating it.
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Save energy by installing an Automatic lighting system in your home. Connect the external lights to the system, so that it turns on the lights in the evening and turns off in the morning. No daily switching is needed and, it will light the premises of home even if nobody is there. It is too small and can be enclosed in a small plastic case.
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Transformer is used to convert high volt AC to low volt AC (Step down) or low volt AC to high volt AC (Step up). So step-down transformer is generally used to convert 230 Volt AC to low volt AC which can be used to make a DC power supply after rectification and smoothing. But a Non polarized capacitor can act like a transformer to step down the high volt AC to low volt AC. Say, 230 V AC to 40 VAC. Let us see how the capacitor is doing this.
Continue reading “How Capacitor functions as a Transformer? Design Note 42”