LED string with timer and printed case
Description
Christmas Is Coming Soon. Take One Of These Simple Battery Operated Led Strings. Mine Was From Ikea. You Get A Nice Red Battery Case, A Power Switch, A Resistor, And A String Of 10 Red Leds With Cabling. No Way You Could Source Alle These Components On Your Own For Less Or Quicker - Unless You Are Planning To Build A 3 Digit Number Of These And Break It Down. Anyway, I Didn'T Like The Simple On/Off Switch. Sure, I Can Switch It On In The Evening, But I Can'T Be Bothered To Remind Myself To Switch It Off Before Going To Bed. A Timer Was Needed. Nowadays, Everything Is Powered By Microcontrollers, Why Not A Simple Battery Led String As Well... The Timer Circuit Is An Attiny45 Microcontroller, Which Is Cheap, Doesn'T Need Many External Components And Was What I Had At Hand. See The Last Picture For The Schematic. The Timer Circuit Does Not Have An On/Off Switch. The Reset Button Starts The Operation (Timer Function). After A Programmable Amount Of Time (See Config.H - Anything From Seconds To Multiple Hours, Mine Is Programmed For 6 Hours), The Led String Is Switched Off And The Controller Goes To Power-Down Sleep Mode (Power Consumption Approx. 0.4Ua At 3V). No Need For An On/Off Switch. Pressing The Reset Button Again Starts Anew. Pressing The Second Button While The String Is Active Switches To Power-Down Mode Immediately. The Firmware Is In The Files. Because The Circuit Did Not Fit Into The Battery Housing, I Printed A Simple Case Which Houses The Strip Board With The Controller And The Two Buttons. The Size Can Be Adjusted (See Params In Scad File). One More Thing: You Can Power This Led String Easily With Used Aa Batteries. I Usually Collect Used Batteries Over The Year (From Toys, Alarm Clock Etc.) - And Use Them Again Here. A Good Re-Use For Used Batteries Before Giving Them Into The Recycling Bin. The Last Picture Shows A Version With 20 Leds And 3 Aa Batteries, Where The Circuit Fits Into The Battery Case.
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