Relay Control

[VTStudent]

Hi,

I am trying really hard to find information on how to control a relay.  I am quite new to the development of LabView programs and have sort of an issue.  I have a system that requires the control of three solenoid valves.  Thre three valves are to be controlled via the relay at specific times, those times being as such: as I take in values of three dimensional wind speed in the z direction, I need to open one solenoid valve when the wind is recorded as negative, while the other two are closed, close the valve and open another one when the wind is positive (with the others closed), and last open a final valve when the wind is neutral (zero) and have the others closed. I also need to keep track of the amount of time that each of the valves is open during the testing period. This is a daunting task for someone who is new to this stuff I think.  Is there anyone out there who could give me some hints on where to start?  I have a fieldpoint with 8.0 software, also, the relay I am using was suggested by NI for the application, it is a cFP-RLY-421, with a cFP-CB-1 connector block. I've already wired up the solenoid valves, and am just not sure how to get my program to control them....help?

Thanks in advance.

Tim Moore
Virginia Tech

[LaurenLL]

Hi Tim,

To help get you started, I would recommend taking a look at some of the examples we have available.  The Digital Output vi located in the example finder is compatible with our FieldPoint Relay modules.  This will simply let you control the relays by flipping a switch on the front panel.  This will obviously need to be modified for your particular application, but should help you get started in controlling the valves and establishing proper communication.

In order to get time information, the best approach would be to work with the timestamp associated with the FP Write command.  This provides the time that the relay actually switches.

I hope this helps.  Regards,

Lauren

[VTStudent]

Lauren,

Thanks for your help! I was wondering, is there a difference between the digital output vi versus analog output vi, just curious, because it seems that most everything I have been working with so far has involved analog devices....maybe not a good question, but just would like to know for sure.

Also, once I have established communication with the device, and enabled the program to open and close the valves using the switches, will I want to modify based on the information above using a case structure type of set-up based on the output of the wind measurment program?

Thanks so much.

Tim

[LaurenLL]

Hi Tim,

A digital output simply outputs either a high or a low value.  This is why it is ideal for working with relays, since you either want it to be open or closed.  You can fulfill the same purpose with an analog signal, although you would need to set the specific output values necessary to switch the relay position.

I have simply given you a basis for controlling the relays.  Once you establish communication successfully, you will need to use LabVIEW to make a program that is specific for your situation.  A case structure could work well if the actions are specific to various ranges of the wind measurement output.

Regards,

Lauren