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control RELE by parallel port of pc

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I would like to construct a device that will be connected to the parallel port of my pc , and i would be able to control RELE's .
I dont know if i can find something like that ready or i should construct it from scratch .
The device must be controlled by a windows programm, that i must construct .This programm would control the device as i want , for example , to enable the rele's as i want , for as long that i want .It should be able to accept schedule for seconds , minutes , or hours .
I dont know wich language should i use to build the program .
If someone knows what should i do at all , please reply, i must construct it since it is part of a medical machine i like to construct.

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Check this as well :


it is much simpler, I have made it many times and works very well indeed. Don't forget the diode parallel to the relay !

If you have win95/98[me=billy]you can control the parallel port directly with the 'out' command. For win2k/xp you need a special driver depending on the language you will use. I have resources for delphi.[/me]

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As Billy has stated, you will need resources for the software. It also depends upon the language you use. C does not do anything you do not tell it to do. Visual Basic sends an automatic line feed and new page unless you tell it not to. If you want to communicate to the outside world from Windows, you will normally need a DLL which will pass the information to the device. If you are using Win XP, you have more problems as you have to get past the built in security. I am assuming you want two way communication.

A search on the web will give you the DLL and how to incorporate it into your code. Look for outport or inpout or combinations of these keywords as I have seen free versions of these on websites in the past.

If this is for medical devices, how are you checking that the relay is closed or open or is not false triggering? Sometimes the parallel port data pins are energized when the computer is turned on. This could be a problem if you are not wanting to turn on a relay that is connected to the port during a reboot or when the computer comes back on from a power failure.

Just some thoughts.


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