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Sebastian writes - "pp_powerSwitch is a TCP/IP based server, which controls a power switching device through the parallel port. Besides Java, I used a bit C to handle the parallel port I/O. I use it for controling heating, lamps, computers, coffee machine and other things (device has eight ports)." - Link.
Parallel port powerSwitch project
Posted by Phillip Torrone |
Apr 13, 2006 09:59 AM
Computers, DIY Projects, Electronics |
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while that circuit I'm sure works just fine, I recommend these changes.
first of all, please use an optoisolator to protect your parallel port - it's very cheap insurance against a very expensive repair ... the parallel port is a logic interface, it is not designed to source power to transistors in the manner depicted.
second, depending on the size of the relays, you might need darlington transistors to latch them. alternately, look into "logic level" N-MOSFETs... these use voltage rather than current to do their switching, and are capable of switching huge loads with 5 volts and nanoamps of current.
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while that circuit probably works fine, I recommend these changes.
first of all, please use an optoisolator to protect your parallel port - it's very cheap insurance against a very expensive repair ... the parallel port is a logic interface, it is not designed to source power to transistors in the manner depicted.
second, depending on the size of the relays, you might need darlington transistors to latch them. alternately, look into "logic level" N-MOSFETs... these use voltage rather than current to do their switching, and are capable of switching huge loads with 5 volts and nanoamps of current.
Reply to this comment
while that circuit probably works fine, I recommend these changes.
first of all, please use an optoisolator to protect your parallel port - it's very cheap insurance against a very expensive repair ... the parallel port is a logic interface, it is not designed to source power to transistors in the manner depicted.
second, depending on the size of the relays, you might need darlington transistors to latch them. alternately, look into "logic level" N-MOSFETs... these use voltage rather than current to do their switching, and are capable of switching huge loads with 5 volts and nanoamps of current.
Reply to this comment
I'm sorry, I'm not too skilled at electronics. In what way does the diode across the relay protect the relay?
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