How do I integrate relays with a NI6009?

[mtcellar65]

Hello,

I am looking for relays to power a project of mine. I currently have a LabView NI6009 DAQ system. I would like to put relays in for two circuits- one is 120 VAC less than 1 amp, and the other is 12 VDC at 4 amps. Can you suggest where I can get two relays that can be switched on and off using my DAQ system?  I found these slim spade terminal ones: http://www.mcmaster.com/#general-purpose-relays/=g4qxj2.  Would these work if I connected them to my DAQ?

Thanks,

mtcellar65

[johnsold]

mtcellar65,

It looks like those relays come in three control variations: 120 VAC, 240 VAC, and 24 VDC.  The UBS-6009 cannot drive any of those.

Your best option is probably a solid state relay (SSR). Many of those can be driven by the digital outputs of the USB-6009. However, finding a DC rated SSR is not so easy.  I did not see anything at McMaster which would work for the DC load.

Lynn

[SnowMule]

An SSR can be driven off a DIO line.  Some work better than others.

Honestly, I'd use a relay driver off the DIOs to sink current through the relays.  A ULN2003A has 7 outputs, more than enough for your application.... i'd use both the SSR and a power relay through the driver.

For the 120VAC side, a solid state relay's probably your best bet.  Omron G3NA's work well, use those often here.  I've driven these off analog outputs on a 600x without any signal conditioning; but since you're going to need a driver anyways i'd run this off a digital line through the driver.

For the 12V stuff, an automotive relay such as  the RLS125 is plenty; those can take well over 10 amps.  That for sure you'll need to use a relay driver to pop the coil over - they use way more current than the DAQ module can source or sink.  Also make sure to put a quenching diode across the relay's coil so you don't have a huge reverse-current spike through the DAQ. 

[johnsold]

Good suggestion about the ULN200x drivers.

Lynn

[mtcellar65]

Snowmule and Lynn,

Thanks for the great info.  I have a couple follow up questions.  First of all I should clarify that this is my first time using SSR's and I am just OK with DAQs.  So here might be a dumb idea-

What if I used two Omron G3NAs connected diectly to the NI USB 6009, as suggested by Snowmule (pretty sure you said I wouldn't need the driver then)?  Then, to get the DC voltage, after the second Omron G3NA I put a 110VAC to 12VDC converter (like a laptop power supply).

Please let me know if I'm way out of bounds here!  Like I said I'm a bit of a rookie at this and appreciate the help!

Snowmule- Do you know which of the Omron G3NAs would work for my power needs and will run off the NI6009?  I looked at their website and came up empty.  Since this is a Senior Design Project I would like to stay as cheap as possible btw.

Thanks again guys- you're lifesavers,

Matt

[johnsold]

Matt,

One of the things you should learn as part of a senior design project is how to read and interpret datasheets.  The art and science of using datasheets is something which is probably not taught in any class, and yet it is soemthing which every design engineer must do on a regular basis.

What I recommend is that YOU figure out which one(s) you think will work, and why.  Post that here and we can confirm before you spend money.  Things to consider: The maximum voltage and current available from the USB-6009, the rated input voltage and current or impedance of the various G3NA models, the output voltage and current ratings of the SSRs.

Whether your power supply approach will work for your DC system depends on your load and your speed requirements.  Some power supplies may come up to voltage slowly or may not even work if they have to heavy a load connected when they turn on. Depending on the load and the amount of capacitance at the output of the power supply, the voltage might decrease slowly when the relay is turned off. It is possible that the voltage could overshoot during start up also.  Since you did not specify the nature of the load and the switching requirements, we cannot advise you directly on this approach.

Lynn

[mtcellar65]

Lynn,

Good advice.  I have been working on other aspects of the project and returned to the relays today.  Hopefully you can still give me the thumbs up.  For the 120Vac circuit could I use this relay: http://www.mcmaster.com/#general-purpose-solid-state-relays/=g8du3i PN: 8299K11?  The current for this will be considerably less than 1 amp so the amp rating will work.  Will the control voltage work with my DAQ, it says the control voltage is 4-28VDC and it doesn't specify a minimum control current?  I would also think that the relay right next to it PN:8299K11 would work for my DC circuit.  The only concern is the max current is 3A, which is exactly what I need for that circuit.

Please give me your opinion, I definitely need the help!

[johnsold]

Matt,

The 8299K11 looks like it would work for you.

One of the few things I do not like about McMaster Carr is that they do not tell you who actaully makes things like those relays or give you a real datasheet.  Look at an electronics distributor such as Digi-Key for other options.

I looked at the Crydom DRACN series which is similar. The DRA-CN024D05 has 3.5 A output to 24 VDC.  The control voaltage is 3-12 V but the typical input current is 10 mA, which is too large for the 6009 DO (8.5 mA).  Also, when you look at the derating curves, you will see that it can handle 3+ A at 20 degrees C but at 30 degrees the rating drops to 2.7 A.

So I would look for a device with a rating of about 5 A.  Try the Crydom DC60S7. Control 3-32 VDC, input current 2.2 mA @ 5 V. Output 3-60 VDC at 7 A.

Lynn

[mtcellar65]

Lynn,

Thanks a ton!

Instead of the 8299K11 could I use the 8192K211 above it since its half the price?  The only difference I can see is that the 8192K211 has a control voltage of 5V (don't know if this will work as well with 6009) but a higher amp rating...

Thanks again,

Matt

[johnsold]

Matt,

As far as the output is concerned, that should be OK.  Again, they provide no information about the input current.

Lynn