How to connect to a relay

[Neka]

Dear Friends,

I am wondering if anyone can help me.

My question at this stage is to get a general procedure to do that.

I am trying to send a signal from my program to a  relay (normally closed). The circuit which I am connecting relay is 6 VAC and 300 mA. My program has a condition and whenever a conditin establishes in my program, I want to send a signal to the external relay and opens it.

1. what is the criterion to choose an assistant device to conncet relay to labview based on my circuit.

2. which relay I should choose (I dont know much about relay).

3. Should I define a specific signal (AC or DC) with specific amplitude and voltage for my relay?

Could anyone give me some information?

Regards,

Mehdi

[walter-donovan]

In general statements, you can use a digital output from a digital I/O board, multifunction board, etc. The digital outputs are meant to drive relays (among other things). What hardware board(s) do you have? In Labview you wire in a function (canned DAQmx vi) for digital output. Look at the write dig chan.vi in examples. In fact, search the examples for digital and you'll see choices of examples that could be close to your needs.

[Neka]

Hi,

Thanks,

I dont have a board right now, dont know what board should be appropriate for my case , usb, or ....

can I buy  usb board for my case?

[walter-donovan]

I'm sure you can but you really should make a well defined list of what you require and talk to an applications engineer to help select the board.

[Dennis_Knutson]

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walter-donovan wrote:

In general statements, you can use a digital output from a digital I/O board, multifunction board, etc. The digital outputs are meant to drive relays...

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That's not true at all. The majority of the DAQ boards have digital outputs that are designed to drive TTL. A relay usually requires more current to operate than a DAQ board provides. A current amplifier/relay driver is often necessary. Pay close attention to the relay type that you purchase.

[Coq_Rouge]

The digital output on most NI boards have drive capability around 15 mA. This may be to small even for a solid state relay. Take a look at this site. Here you will find som hints in driving relays with transistor. http://www.me.umn.edu/courses/me2011/robot/technotes/motorcontrol/motorcontrol.html You may also look at cheap ULN2000 series circuit.

good luck

Message Edited by t06afre on 02-08-2009 01:08 PM