How do I integrate relays with a NI6009?

[mtcellar65]

Lynn,

I bought the SSR from McMaster but ran into a slight problem.  When I hook it up to the DAQ I wired the - terminal to the DAQ ground and the + terminal to P0.0.  After I switch that line on it only supplies 1.21V and the relay doesn't switch.  If I take the wire out of P0.0 and plug it into the 5V supply on the DAQ the relay switches.  So the relay works with that 5V supply but I am wondering why it won't work when plugged into the lines.  It pulls 1.21V off all the lines so I am assuming that those lines supply just as much power as is needed by the DAQ.  How can I make them supply 5V?  Also, am I hooking this up the correct way?

Thanks again for the help,

mtcellar65

[Dennis_Knutson]

You've been told about the importance of the input current rating. If the relay requires more current than the DAQ device can provide, the voltage will drop. Perhaps you want to use the relay driver mentioned earlier and find an electrical engineering student to give you some help.

[mtcellar65]

Thanks for the post Dennis,

I talked to the supplier and they said the relay I have will need less than 1mA.  I don't know how true this is but I believe them.  This link is from NI and is doing the same thing I am.  I even am using an Omron 5VDC SSR like they do.  It is an Omron G3NE-205T-US.  From what everyone has been telling me this relay should work.

[johnsold]

The USB-6009 can sink (switch current to ground) 8.5 mA with 0.8 V drop across the DO. In the Open Drain (Open Collector) mode it can only pull up 0.6 mA and the voltage can be as low as 2.0 V.  In push pull mode it can supply 8.5 mA but with 1.5-3.0 V drop.  This information is all in the specifications for the USB-6009.

Operating in sink mode is your best choice.  The + end of the relay input goes to the +5 V from the 6009.  The - relay input goes to the DO output (P0.0 or the line you choose).

Lynn

[mtcellar65]

Lynn,

I could not be more grateful!  It worked like a charm.  I hooked the 5V output to the + terminal and the P0.0 to the - terminal.  I set the P0.0 as an outptut and controlled it with a switch.  Do you guys foresee any problems with this setup for continued runs?  If I hooked one more relay up with similar power requirements to the 5V power and P0.1 I should be able to switch that as well correct?

[johnsold]

Matt,

You should be OK with two SSRs connected to separate lines.  I do not recall if there is a published limit as to how many lines can be loaded simultaneously, but I doubt you are close to it.

Lynn

[aeastet]

Keep in mind with the USB-6009 you can not set the start state of the relay. It will com on in what ever state the daq card starts in. If starting state for this application is important you need to be careful.

[mtcellar65]

Tim and Lynn,

Thanks for the warning.  I guess here was my thought- if I started and ended the DAQ with the voltage at 0, won't it start at that same value?  Right now I have it hooked up as Lynn mentioned a couple posts ago with a LabVIEW switch controlling it.  I am going to turn this switch on and off a number of times.  At the end of the day I plan on turning this switch to the position that will have the DAQ output 0 volts.  When this is the case I will cut power to the system.  If I come back the next day and restart my .vi, will that switch still be in the position for the DAQ to output 0V?

Thanks,

Matt

[aeastet]

Even if you try and start and stop in the same position there is nothing that will force this to zero even if you put it there and shut down. If you read the manual for this device it does warn you that the position of the digital channels can not be set for start up. You need to be careful with this device if someone can get hurt if it is not in the correct position.

That is all I am saying.... be careful

[EENerd]

Try McMaster :

4-28 DC	3 @ 12-280V AC	8299K11	29.42
4-28 DC	3 @ 5-60V DC	8299K12	28.37