powering circuit using DAQ card

[jackkk]

Hello guys,

I am using an EMANT 300 Light Adapter.

I wish to power a external circuit that is connected to the DAQ using the DAQ.

Further Explaination:

Once my LabVIEW program reaches a certain condition, it will give a voltage and power up the external circuit. Is it possible?

Thank you and regards,
Jiaxuan

[RavensFan]

Probably not.

Which DAQ card are you using?  How much current and voltage does the external circuit require?  With the Daq card, you might be able to turn on a relay to apply power to another circuit, but unless the external circuit requires a low voltage (~5VDC) and very low current, I doubt you could drive that circuit directly.

[jackkk]

I am using Light Application Adaptor for EMANT300.

The external circuit could be powered by a normal 9V battery. But the circuit needs only 5V. Current should not be a problem?

I am not very sure about it/

[Matthew_W]

 Hi Jackk,

 Are you using the EMANT300 DAQ?

 If so then support for that product can be found at the manufacturer's website here.

 If you are using a NI DAQ then which one? How much current does the EMANT300 Light Application Adapter require at startup and run-time?

 We can tell you if your NI DAQ has sufficient current to power this device if you can provide us with that information.

 Have a great afternoon!

 Best regards,

 MatthewW
 Applications Engineer
 National Instruments

 

[jackkk]

Hello,

Thank you for your help.

Yes I am using the Emant300 DAQ connected to the Emant  300 Light  Applications Adapter and is then connected to the USB port of the computer.

If the Light Applications Adapter depends the external circuit current to power it up, the current is dependant on the 9V Energizer 522 Battery and it varies. (around 3A)

This is the 9V Energizer 522 Battery PDF.

Regards,
Jiaxuan


Message Edited by jackkk on 12-04-2007 09:10 PM

[Matthew_Kelton]

You do NOT want to power your circuit from your DAQ card.  Regardless of voltage/power requirements, do you really want to damage your DAQ card because your circuit has a short or some other problem?

Add a relay to your circuit which you can turn on and off via the DAQ device.  Then have the relay switch the power on and off.  Then you can use your 9V battery or an external 9V power supply.  That way, unless your circuit really is screwed up, you blow out a $1-$5 relay instead of an expensive DAQ card.

[jackkk]

I see, but how do I connect the relay to the EMANT300? Is there a certain function in LabVIEW that I have to use?

And I understand that there are various types of Relay - will the general ones do?

Sorry for the trouble

[Matthew_Kelton]

You connect the + coil to one of your digital outputs and the negative side to ground.  You need a relay that has a coil voltage that will trigger between 3-5V.  You can get a better idea yourself by looking at your DO and seeing what the voltage is.  You need to make sure the coil doesn't require more than 20mA.  If you need more than 20mA, you'll have to look at transisitor circuits, but then you probably should look at just using the transistor, assuming you don't need too much current from your 9V power supply.

Just make sure the realy meets the requirements (9V at your cicruit's current draw), probably a 5V coil, <20mA.  You should be able find numerous types from SSR to PCB mount relays that meet your needs.

[Matthew_W]

 Hi Jackk,

 After you connect a relay to the EMANT300 DAQ then you will use a LabVIEW vi to write the digital output. I took a quick look at the LabVIEW VI's that EMANT provides,
 it appears that the EMANT300 Write Digital Bit.VI can be used to do this.

 What MatthewK is saying is correct, you want to be very careful not to pull too much current out of your DAQ device. The safest way to isolate your DAQ from a high current demand is to use a relay, FET, something like that.

 Have a great week,

 MatthewW
 Applications Engineer
 National Instruments
 
 

 

 

[kychan]

You may want to look at the app note here.

http://www.emant.com/80050.page

Note that if your relay coil requires more than 20ma or more than 5V supply, then the ULN2003 is required. Look up the stepper motor app note. Replace the stepper motor coil with the relay coil.

http://www.emant.com/80140.page