voltage out from parallel port

[vlonjati]

Hi there,

I want to use the parallel port to run a relay.

I do not understand the example given by labview. I also read the forum but I did not see what I am looking for.

I am kindly asking if some one can write a small program ( I use labview 8.5) so I can give a 5v out say to pin #2.

Thank you in advance

[Coq_Rouge]

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vlonjati wrote:

I do not understand the example given by labview. I also read the forum but I did not see what I am looking for.

I am kindly asking if some one can write a small program ( I use labview 8.5) so I can give a 5v out say to pin #2.

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Please tell us more why you struggle, this is not good enough

[smercurio_fc]

The voltage out of a parallel port is not necessarily 5V. Modern motherboards usually only have 3.3V, if they even have a parallel port. Besides the voltage, the current is more crucial. What kind of relay are you trying to use? The parallel port is not a power supply, and it cannot source or sink a lot of current. It is not designed to power relays. It is designed to interface to logic chips. Your next question will probably be: how much current can I source or sink with the parallel port? The answer is that it depends on the motherboard. You will have to check your motherboard's specifications.

A far better solution is to use some sort of driver circuit or a DAQ device. Please perform a search on this forum, as this question comes up very often, and the answer is always the same. 

[vlonjati]

Guys ,

Thank you both. I actually solved the problem. It was easy I could not understand what value shout I send to the pins.

Now I know I need to work in the system with base 2.

Smerucurio I am aware of the information you gave but thanks. In order to run the relays I put in series with the pins a resistor of 5K

so the current never exceeds 1ma and I connect it in series with a transistor of gain 50 so I get enough current to run it.