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Sunset Lamp. Design Note 45


Many people leave the outdoor lights switched on as a safety measure while going for a long journey. The light will be on during day time also wasting lot of power and money. So here is a simple solution to avoid this. This circuit lights the premises of your home even if you are not there. It is fully automatic and turns on  Bulbs or CFLs at Sunset and turns off at Sunrise. So no need for daily switching. The circuit can run 250 watts load so many lamps can be connected. It is too compact and costs only Rs. 50 without power supply and the total cost will be around Rs.150. So once it is connected, we need not remember to switch on / off the outdoor lights. It will do its job at the right time.
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Selection and use of Capacitors Circuit Clinic 2


Let us move to the world of capacitors. You can see a number of capacitors scattered here and there in the circuit board starting from the front end to the last. These capacitors are doing lot of job in the circuit like smoothing, filtering, coupling, de-coupling, buffering etc. You can also see the size and shape difference. The capacitors may be electrolytic or disc but the structure is identical in both having two electrodes separated by a dielectric material. But the functions will be different. For example, a Smoothing capacitor in the power supply section will remove ripples from AC to give a clean DC while a capacitor in the audio circuit acts as the noise filter. So the selection of capacitor and its use in the different parts of the circuit is important. Electrolytic capacitors are polarized so always connect with correct polarity otherwise, it will explode. Disc capacitors are non polarized so they can be connected either way round.
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