06-05-2011, 12:23 PM
Many articles have been publishedin EFY for controlling devices through a PC’sparallel port or line printer (LPT)port. Here is another project for controllinga school bell or a scheduledshift-timing alarm of a factory automatically.The load connected to theoutput of the project can be an electricbell or a hooter. The timing canbe programmed for every day scheduleas per individual requirement.A Windows-based program developedin Microsoft Visual Basic programminglanguage is used for controllingan electric bell or hooterthrough an electromagnetic relay. Ithas been designed for Windows XP.The graphics have been includedso that the master clock shows the realclock time on the PC’s screen. At thesame time, it shows alarm clock timingfor triggering the timer circuit foractivating the bell or hooter.The alarm timings, ‘on’/’off’ controlsand their activation sequence canbe set by the user as per his requirementthrough 48 numbers of settings—that is, 24 settings for alarm time displayon the screen and 24 for enablingor disabling thetimer circuit.The alarm timeas well as bellor hooter ‘on’/’off’ timer canbe set bysimple clickingthe bigger rectangularbox and a small square box on the top ofthe rectangular box, respectively. Theprogram output user interface isshown here in the screenshot.
Hardware interface
Fig. 1 shows the block diagram of theautomatic time manager (ATM) andFig. 2 shows the circuit diagram of theinterfacing unit. Here, we are concernedwith only two connections: pin2 and a ground pin of the parallel port.Pin 2 corresponds to the first data bit‘D0’ in 8-bit data bus of the parallelport.The whole unit is powered by a6V DC regulated supply. LED1 is thepower-’on’ indicator.IC MCT2E isolates the PC from themain interfacing unit in case any shortcircuitoccurs. Thus, it acts as a safetydevice and protects the PC.
Download full report
http://kitsnsparesadmin/pdffiles/Automat...anager.pdf
Hardware interface
Fig. 1 shows the block diagram of theautomatic time manager (ATM) andFig. 2 shows the circuit diagram of theinterfacing unit. Here, we are concernedwith only two connections: pin2 and a ground pin of the parallel port.Pin 2 corresponds to the first data bit‘D0’ in 8-bit data bus of the parallelport.The whole unit is powered by a6V DC regulated supply. LED1 is thepower-’on’ indicator.IC MCT2E isolates the PC from themain interfacing unit in case any shortcircuitoccurs. Thus, it acts as a safetydevice and protects the PC.
Download full report
http://kitsnsparesadmin/pdffiles/Automat...anager.pdf