Electromechanical Timer Replacement - 320Volt

The Galactic TimerElectromechanical TimerReplacementAuthor:OVERVIEWMichael KirkhartGSE. Inc.Farmington Hills, MIUSAemail: kirkhart@rust.netThe Swiss Army Timer is a generic, programmabletimer circuit which can electronically replicate the functionalityof some of the more popular electromechanicaltimer relay circuits. Using a PIC12C508 along with a24C04A serial EEPROM (for configuration storage), theSwiss Army Timer can function as an on delay timer, offdelay timer, one-shot, re-triggerable one-shot, astablemultivibrator, and enabled astable multivibrator. Itsevent counter and auto-resetting event counter modescan replicate the function of an electromechanicalcounter as well. It uses two inputs (a timer input andtimer reset input) and has one output. The two inputsand the output can be programmed to be either activehigh or active low, and the active edge of the timer inputcan be programmed to be either low-to-high or high-tolow.Time intervals can be programmed from 0.1 secondsto 6553.5 seconds, and terminal counts can beprogrammed from 1 to 65535.MODES OF OPERATIONThe Swiss Army Timer can operate in one of the followingeight modes:• Mode 1 - On delay timer: When the timer inputgoes active, the output waits for N seconds beforegoing active. When the timer input goes inactive,so does the output.• Mode 2 - Off delay timer: When the timer inputgoes active, the output goes active. When thetimer input goes inactive, the output waits for Nseconds before going inactive.• Mode 3 - One shot: When an active transition ofthe timer input occurs, the output goes active for Nseconds. If another active transition of the timerinput occurs while the output is active, it isignored.• Mode 4 - Retriggerable one shot: This mode issimilar to the one shot mode except if an activetransition of the timer input is detected while theoutput is active, the output will remain active for Nseconds after detection of the transition.• Mode 5 - Astable multivibrator: This mode replicatesthe action of an oscillator. The output goesactive for N seconds, and then goes inactive for Mseconds. This sequence repeats indefinitely.• Mode 6 - Enabled astable multivibrator: This modeis similar to the astable multivibrator mode exceptthe sequence is reset and the output is held inactiveif the timer input is not active.• Mode 7 - Event counter: Each active transition ofthe timer input is counted. When this countreaches N counts, the output goes active andremains active until the timer reset input becomesactive. When the timer reset input goes inactive,the accumulated count goes back to zero. Thecount is reset any time the timer reset input goesactive.• Mode 8 - Auto-reset event counter: This mode issimilar to the event counter except, the next activetransition of the timer input, after the terminalcount is reached, will automatically reset thecounter and deactivate the output. The timer resetinput can still be used to manually reset the accumulatedcount.Microchip Technology Incorporated, has been granted a non-exclusive, worldwide license to reproduce, publish and distribute all submitted materials, ineither original or edited form. The author has affirmed that this work is an original, unpublished work and that he/she owns all rights to such work. Allproperty rights, such as patents, copyrights and trademarks remain with author.© 1997 Microchip Technology Inc. DS40160A/1_005B-page 1