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Parallel Port output device to control low Voltage equipment

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Gabrielle

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Hi All, firstly let me appologize for my total dumbness and thank you for helping me in anyway you can.

What im doing is trying to build a simple parallel output device, that can be use to control different household items. Now, I've spent lots of time online surfing, and found http://www.hut.fi/Misc/Electronics/circuits/parallel_output.html after reading and researching alot of posts on your site. Now my problem is this, due to the fact that its been like 20+ years since i took Control Technology at school, I don't know what some of the symbols are on the circuit diagram :( (Im sorry.. but im trying to understand it and get back into to electronics so during the day when alone i have something to tinker with - who said mum's just read and watch tv hehe)

What im asking I guess is this, the diagram that im reading and re-reading is confusing me on the components needed, and also once I know whats what, then need to find some good software, to design the board, and test it, so i can show it to a sales person at maplin so not to look a total dumb blond. :lol:

The diagram is the last one the Optosiolated higher Power Circuit on the site, and its the last diagram thats presented before the code at the end.

Any and ALL help is greatly appreciated.

Yours
Gabrielle
 

Mosfet

New Member
Text circuit diagrams are confusing for me also.
Maybe this picture will help.
The relay type will depend on what you are switching.
The unmarked transistor will depend on the relay.
Regards.
 

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Gabrielle

New Member
Thank you EVER so much, thats truely appreciated.. brilliant!!! one last question, before I run off to start my scheming on my husband... Erm oops I mean to help him :lol: what software would you recommend for testing diagrams.. I've read that some of you design a circuit, then test it in a program, to ensure it works correctly ? i've been searching all day for something to do that with no success..

Thank you again Mosfet, your help is really appreciated.
Gabrielle
 

Gabrielle

New Member
I do have one question, been sat here thinking actually, when you say unmarked transistor and relay type will depend upon what im switching, this is making me really think long and hard.

The device that this will be controlling now will be a simple light that opperates of a 2AA batteries which is connected to a small lead with a simple 2 state switch (on/off. Going to connect the ends of the output from the circuite to it) so I can turn the light on and off from the computer.

The question is. If i was only opperating something upto around 4x AA batteries, would the relay have to be altered ? or would one cover a little range ? and if so.. could you advice as to what the last to components would be ?
 

Mosfet

New Member
Here is a diagram for a common 12 volt relay.
http://support.radioshack.com/support_supplies/doc9/9525.htm
Note that the nominal current to control the electromagnet which pulls the relay's main contacts is 75 milliamps.
Please also note that the relay's main contacts will control a current of 15 amps. [15000 milliamps]
In essence one is using a small current to trigger a switch with a current rating 200 times as large.
The transistors the author mentions, TIP41C & 2N3055 control 6 & 15 amps respectively.
A relay that needed, say, 10 amps to trigger could possibly control 2000 amps or more!
This is enough for a small electric locomotive.
This is a bit overkill for AA batteries.
You may wish to use the circuit with one lone BC547 and a small relay as above.
Regards.
 

Gabrielle

New Member
Great!! thank you.. my first design stage. (With ALOT of help) complete.. now for the fun part... yay!! making it ...

Thanks again Mosfet.

Now to buy lots of solder, and make solder balls like i did at school while trying to think.. Oopss - Ducks from the yells and screams of waisted solder
 

Mosfet

New Member
The link you provided has a simpler circuit which may be better for you.
"Circuit with optoisolation -
If you want to have a very good protection of the parallel port you might consider optoisolation using the following type of circuit:"
As I said "You may wish to use the circuit with one lone BC547 and a small relay"
 

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Gabrielle

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Great Mosfet :) thanks once more. guess ill have to make that one and see if it works once more.. :lol:
 
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