| Author | Message | | | eric | | Posted: Mon Aug 28, 2006 10:45 pm Post subject: Mailbox Alarm | | | | Site Admin Joined: 01 Jan 1970 Posts: 311 | Pradeep G.
Here’s a 555-based project that can be used as mailbox alarm.
By suitable mounting of the LED and the phototransistor, the circuit
is able to detect when a letter is dropped in your mailbox.
Our younger readers should know that a ‘letter’ is not the
result of hitting any of the A-Z keys on the PC keyboard, but
a precursor of the email message. For some mysterious reason,
some people are still sending messages to each other using
letters. In case you’ve never seen one, a letter is usually contained
in an ‘envelope’, it takes ages to deliver and can sometimes
be seen in the hands
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