please help on parallel port

hi
i want to connect a tea dispenser to my parallel port of the comupter .
the tea dispenser has a microcontroller which controls the motor (for
powder dispensing) and a valve for hot water dispensing.
what should my new parallel port diagram look like?
i am very new to these things and its sort of urgent.
thanks in advance

impromptu.guitarist@gmail.com wrote:

Lee

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On 11 May 2006 05:46:18 -0700, impromptu.guitarist@gmail.com
wrote:


LOL. Why didn't I think of that!



Powder?
blasphemy

Hook up a grow light for the leaves, one of those birds the
flintstones use to harvest, a peltier and fan array to dry
the leaves, a grinder and then a heat lamp to turn it into
sun tea. Parallel ports might show their weakness here, I
suggest USB2.


Try it like this:


All kidding aside, you're almost as insane as I am.

"kony" wrote:
wrote:

Blasphemy! Tea leaves need to be properly fermented for the best cup of
tea. This will require a timer application, a "slicer/dicer", a humidity and
temperature controlled area, and finally a heating element to "fire" the
leaves to the proper amount of moisture content.

Jon

impromptu.guitarist@gmail.com wrote:


The first thing to remember, when connecting devices, is the
dangers associated with interconnecting signals from one
device to the other. The person who designed the tea dispenser,
may not have planned on "user modifications". The devices may
have different ground potentials, and the parallel port
interface on the computer could be damaged by your tinkering.

There are probably a ton of web pages available, for building
interfaces to a parallel port. The parallel port uses 5V
TTL logic levels. The safest way to connect between the two
systems, is with a relay. Figure B and Figure C at the top of
this page, give you a switch contact to play with. For the relay,
you select a relay with a reasonably small coil current requirement.
The 1N4002 is used as a snubber, to absorb the back EMF from the
coil when it is de-energized. The 1N4002 must be present, if
the thing is to survive for a while.

http://ourworld.compuserve.com/homepages/Bill_Bowden/page6.htm

For maximum protection, you can buy a preconstructed I/O
product that connects to the parallel port. The outputs
on these things are switch contacts, so you cannot bugger up
the computer if you use one of these. Buying a solution
this way, avoids the messy selection process for the relay.
Just connect the switch contacts from the relay, to whatever
needs switching on and off.

http://www.electronics123.com/s.nl/it.A/id.1713/.f?sc=8&category=35

The relay coil is isolated from the switch contacts. That means
there is (practically) no way for current to flow from the
tea dispenser, into the computer, or vice versa.

Paul