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25-07-2017, 10:02 AM

Please provide documentation of electronic letter box,and about motivation of electronic letter box.

jaseela123d · 29-07-2017, 10:53 AM

The circuit described here can be used as an electronic mail box. When someone drops the letter in your letter box then the LED connected to the output outputs glowing indicating you have letter. To detect the presence of a letter we have used an LDR and a light source. It has a resistance of approximately 1 mega ohm in total darkness and 2-5kohm in bright light. In this the light source and LDR is thus set in the mail box that the light will fall will fall directly into LDR so that when the letter falls into the box it will block the beam of light and LDR will be under darkness. Visual alarm when someone drops a card in their box. This electronic circuit of the letter box is based on the operational amplifier LM741, CD4001 and LDR. An op-amp produces an output voltage that is hundreds of thousands of times larger than the voltage difference between the input terminals.

Circuit diagram:

[Image: electronic%20letter%20box.gif?itok=-GIuQYMq]

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