i want to transmit a square pulse through USB port, is it possible?? if not then what is the best way to do that, preferable is with serial then parallel, and its compatibility with vista,XP,and @))7 windows

[smercurio_fc]

And not to mention the many different kinds of relays...

[Ray.R]

I've used telecom relays (can't remember the model designation), which worked fine in the past with older PC using the parallel port.  I've never heard of / or tried using the serial port.  I wouldn't expect it to work as expected... (I'm not going to go into details).  I suspect driving a relay from a USB port would have similar issues as the serial port.

However, recent motherboards do not drive the telecom relays as they used to.  I've seen a recent Dell motherboard have problems with it.

[Coq_Rouge]

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Ray.R wrote:

I've used telecom relays (can't remember the model designation), which worked fine in the past with older PC using the parallel port.  I've never heard of / or tried using the serial port.  I wouldn't expect it to work as expected... (I'm not going to go into details).  I suspect driving a relay from a USB port would have similar issues as the serial port.

However, recent motherboards do not drive the telecom relays as they used to.  I've seen a recent Dell motherboard have problems with it.

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I was thinking about using the control lines (DTE ready, and Request to send on a 9 pin) That was why I asked about the numbers of relays. That will work as expected with some driver circuitry (I'm not going to go into details).  Perhaps a somewhat odd solution, I shall admit that ;).

[Ray.R]

Okay...  That's an interesting approach...  I was wondering if I had missed something somewhere....  😉

[Coq_Rouge]

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Ray.R wrote:
Okay...  That's an interesting approach...  I was wondering if I had missed something somewhere....  😉

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Very well then. Apology axcepeted (with some muttering):smileytongue:

[Coq_Rouge]

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Ray.R wrote:
Okay...  That's an interesting approach...  I was wondering if I had missed something somewhere....  😉

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Very well then. Apology excepted (with some muttering):smileytongue: 

[Intaris]

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Ray.R wrote:

I suspect driving a relay from a USB port would have similar issues as the serial port.

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Nope.

While you might be able to do something like this with Serial or Parallel, USB simply won't play along because you never have direct access to the levels of the signals.  You interface through a controller chip which takes care of everything and only understands "USB".

Shane.

[Ray.R]

Thanks Shane.

That rules out USB.  Unless there is a DAQmx device at the other end.  But that would have to drive a small (telecom) relay, because it derrives its power over USB.  Don't quote me because I'm wrong, but I suspect the current would be limited to something like 25 mA.

[Intaris]

USB 2.0 supplies 500mA.

Enough to dirve many portable hard drives, but it's not simply switchable unfortunately.

USB 3.0increases power supply to 900mA.

Shane.

[AnalogKid2DigitalMan]

USB powered and controlled relays, LabVIEW drivers available:

http://www.easydaq.biz/PagesUSB/USBRelayCardProductsFRAME2.htm

-AK2DM