controlling many switches from the PC

I would like to control arund 100 electric switches from my PC.
Can someone guide me on this.
Thanks in advance
Arun Sahlam
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You can do this with the standard parallel printer port. It's easier if your system uses Win9x or DOS, but should work from NT,2K, XP with an IO driver so you can get access to the port.
The standard port has only 8 output lines, but it also has several control lines. The trick is to make a multiplexer 8-bit latch chips. Use 4 control lines to select one of 16 latch chips to be updated from the common 8 lines. That will give you 8 * 16 = 128 possible outputs.
There is lots of port info at
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Hope this helps!
Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis
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Bob Masta
Try reading up on X10 at
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They have a controller that attaches to your PC and the switches you'll need.
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Bruce Robin
well how do you want to control them.? and what sort of switches are they.? and what do they control.?, what kind of hardware do you have hooked up to your computer at the moment.???......You could use a microcontroller to do this, but some information regarding your existing infrastructure would be useful
Reply to
Maurine O.
This like asking "How can I get to work?"
What sort of switches, what sort of electric devices, what voltages, what wattage, what distances, etc..
Ask better questions and you'll probably get better answers.
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There is a book, perhaps out of print, from TAB books "Building Your Own Universal Computer Interface" by Bruce Chubb, that would provide a bunch of outdated information to get you started. The ISBN # is 0-8306-3122-4.
Also, a look at the data sheet for an 82C55 programmable interface controller is interesting for historical content. It will point out the many good reasons for using a micro controller.
Maurine's questions are also valid. On what level of interface are you looking to implement? Parallel port? Serial port? Mother board plug-in card? Speed? Then comes the question of user interface software on the PC. Is this something that you would prefer "off the shelf", or will you develop this application software?
Reply to
JL Hart
If you want industrial strength safety and ease of use, go with an I/O card that you can plug into your PC. There are many vendors, and
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is one of the popular ones. The others you would have to google.
Most of these cards have multiple output options including relays and SSR that you can use to control almost anything. They also have drivers, samples and everything you need to get going fast.
Hopes it helps,
Thomas Yip
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this might help, and you might go nuts and use a tcp stack chip too. but you could just use a stack chip and get a matrix of 256 switches from it anyway.
Reply to
jim dorey
The below link has info on controlling 300+ christmas light strings from the parallel port.
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Si Ballenger (Bob Masta) wrote in news:41af2700.3580034
I did this with my very first computer for a science fair project back in 83....a Tandy Color Computer....had a whopping 16K of extended memory...but more had a game port... I built a card to plug in the port..used opto-isolators...through some latches..and on to some high-capacity triacs..would switch 16 120VAC loads...I just hooked up 16 lamps for the project...but you could have ran your household appliances from it. BTW...I've still got the old color computer :)
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