Doorbell MemoryCircuit

  
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If you`re expecting an important visitor but you just have to step out for a moment, an electronic doorbell memory can come in handy so you can see whether someone rang while you were out. Of course, you can`t tell whether it was the visitor you were expecting who dropped by then, but a call to the mobile phone of the person concerned can quickly
Doorbell MemoryCircuit - schematic

answer that question. A doorbell memory can also save you the trouble of going to the front door (if you live upstairs) when you think you heard the bell but aren`t sure. And if you can`t buy one, then of course you can build one yourself! Read on to find out how. It takes only a handful of electronic components to build a handy tale-tale with an LED that indicates whether someone pressed the button of your doorbell. How many times have you thought you heard your doorbell while watching television in the evening The sound of the well-known ding dong` chimes occurs all too often, especially during the many commercials that nowadays remind us at the most inconvenient times that the gripping film we`re watching is only a fantasy. A glance at the LED of the doorbell memory will tell you whether you have to go to the door or can try to escape the ads by zapping to a different channel. Or if you`re expecting someone but have to make a quick trip to the neighbors to borrow a few beers for the occasion, it can be handy to be able to see whether your visitor already arrived while you were out. If so, you can always call him or her on the mobile to confess that you hadn`t properly prepared for the expected visit. The circuit is as simple as it is effective. It is connected in parallel with the bell and powered by a 3-V supply formed by two 1. 5-V penlight batteries connected in series. The doorbell memory draws so little current that...



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