Larry's Overdue Bill Warning System Needed Work

By: 
March 03, 2003

Fido's out of the doghouse now, thanks to Larry's automatic mail delivery notification system. When the postman opens the lid of Larry's mailbox, a photodetector mounted inside the mailbox activates a light-emitting diode inside the house, notifying him that mail has arrived. A special latch circuit ensures that the LED stays lit after the lid shuts, and a pushbutton allows Larry to reset the circuit after retrieving his mail.

Are you a Gadget Freak? Allied Electronics would like to send you on a shopping spree of up to $500 on its website at www.alliedelec.com/gf.asp. Email Design News your proposed project (must incorporate electronic components and involve sensing, motion, timing, and/or networking elements) to [email protected], along with a description of how it works, and a parts list. If your project is selected, you'll receive the shopping trip of up to $500 and be featured in an upcoming edition of Design News.

Mail's Here! Parts List
Amt Part Description Allied Part #
1 Ceramic Capacitor, 1.0 muF 881-5236
1 Ceramic Capacitor, 0.1 muF 881-3486
1 RED LED 670-1065
1 NPN Transistor 935-0841
1 CdS Photocell 980-0105
2 Carbon Resistor, 22 k 296-6330
1 Carbon Resistor, 1 k 296-6314
1 Carbon Resistor, 10 k 296-6326
1 Carbon Resistor, 1 meg 296-6348
1 Normally Open Pushbutton 757-2305
1 CD4011 Quad NAND 735-1323

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