BNC-2110 can power a 5V mini relay?

[NeuralJ]

Hi,

       I hope you can help me with my first engineering problem. I'm working on a fluid delivery system in which a computer program sends a signal to power a 5V relay. The relay in turn switches on a 12V power supply. The power supply then switches on the fluid pump.  Here are the issues:

1.) We were told by the software designer that the computer's parallel port would send a TTL pulse strong enough to power the 5V relay. However, his program's maximum output is 3.5 V, and as a result, the switch will not turn on.

2.) He then said that there might be a way to get a 5V from a digital output from the BNC-2110 box. which is also controlled by his program.  Can this be done? If so, how?
     Looking at the box, the only guess I can make is connecting the relay to the terminal block labeled "5V." How would I go about making this connection? Soldering?


Thank you very much for your help. It will be greatly appreciated.

[Travis G.]

Hello NeuralJ,

The BNC-2110 is a terminal block that simply provides access to the lines on a data acquisition card in your computer.  You can use the BNC-2110 with most National Instruments Multifunction DAQ devices.  The screw terminals on the upper-right of the BNC-2110 provide access to eight digital lines on your DAQ device, and these digital lines output TTL signals of 0 or 5V.  Depending on the programming language you are using, you can find example programs that will show you how to write on or off values to the digital lines on your DAQ device.  Within LabVIEW, you can find examples in the NI Example Finder by going to Help > Find Examples.

One issue you will need to investigate is the current required to drive your relay.  A DAQ device draws power from your computer's power supply, and can only source a finite amount of current.  You can find information about the current sourcing capabilities of the digital lines on your DAQ device in the specifications section of the user manual.  These specifications are also linked from most of the main product pages for the DAQ boards on www.ni.com.  Let me know if you need some help finding these specifications.

Regards,
Travis G.
Applications Engineering
National Instruments
www.ni.com/support

[NeuralJ]

Thanks, Travis.


I'm having trouble finding the specifications. How exactly do I go about finding out how much current is available through my computer?

[NeuralJ]

Hi Travis,

    We are using the 6025E NI-DAQ card. I believe it has an analog output of +/- 10 V and a driver current of +/- 5mA. I'm not exactly sure about the Digital and Timing I/O output current specs.

   What would be the best way to wire a connection to the Digital and Timing I/O terminals? And which specific terminals should I use (does that depend on the software)? The only wiring I've ever done is soldering.

  I appreciate your help; this is my first venutre into computer and electircal engineering, and I would like to learn how to effectively best use your products.

[Travis G.]

Hello NeuralJ,

Your PCI-6025E device has 32 individual digital I/O lines, grouped into 4 ports of 8 lines each (port0, port1, port 2, and port3).  It is one of the few E-Series DAQ devices with extended digital I/O lines, and because of this has different current sourcing capabilities depending on the port used.  

Your PCI-6025E connects to the BNC-2110 terminal block using a 68-pin cable.  The BNC-2110 breaks out these 68 lines on your DAQ device to BNC connection and screw terminals.  The BNC connections are used for analog input, analog output, and a few other special connections.  The screw terminals provide access to the first 8 of the 32 digital lines (port0) and other specialty lines called PFI lines.  The screw terminal labeled P0.0 through P0.7 provide access to the digital lines of port 0 on your 6025E.  You'll need to connect the lines of your relay between one of the digital line screw terminals and one to a D GND (ground) terminal.  You can then use LabVIEW or some other programming environment to toggle that digital line between low (0V) and high (5V) in order to turn the relay on or off.  Within your programming environment, you can write a program to toggle each line individually, so just pick one digital line and use that.  For starters, you can use the test panels in Measurement & Automation Explorer (MAX) to toggle the digital lines to see if everything is connected properly.  Within MAX, find your device under Devices and Interfaces > NI-DAQmx Devices, right-click on it and select Test Panels, click on the digital I/O tab, set the lines to output, and toggle them with the switches on the test panel.  

I hope this information helps and let us know as the questions come up

Regards,
Travis G.
Applications Engineering
National Instruments

[NeuralJ]

Hi Travis,

   I believe I'm ready to try the circuit out. Please correct me if my logic is flawed:

1.) From my 3rd party software, specify that I want 5 V to be powered to port 0 of the DAQ card.

2.) Connect my relay to the BNC-2110, by placing one lead into P0.0 and the other lead into D GND.
     Does it matter what lead is put into which spring terminal? Also, I was able to to connect the wire to the spring terminal by pushing the wire in until the yellow piece next to the opening dipped down. Is this correct?

3.) Solder the wires from P0.0 and D GND to the coils of my relay.


As an aside, is there a way I can have MATLAB interface with the 6025E? We are getting annoyed by our 3rd party software designer, and we have people in our lab who are fluent in MATLAB coding.

[Jeff_T.]

Neural J,

I've been following your issue and the logic looks good.  Best of luck!

Regards,

Jeff Tipps
Applications Engineer
National Instruments

[NeuralJ]

Travis, thanks for all your help. The circuit works!

[NeuralJ]

Thanks, Jeff. The circuit finally worked yesterday!

[NeuralJ]

Hi Jeff,

 I have to give a presentation to a bunch of 5th graders at summer camp about the project. What would be the easiest way I could explain what a "port" is and what a "line" is? I'm stuck as to how to make the NI equipment as easy to understand in the simlest way possible.