How control a relay using the ni usb 6008?

[Tom__Sedlack]

Are you required to switch the relay with the transistor?  Unless there are current or voltage limits I just don't see, the opto-isolator can do the relay control.  I attached a simplified schematic.  Component

values and the lamp are not listed for clarity.

[Tom__Sedlack]

I thought about this on the way home from work.  The circuit diagram in the last post should work for simulating.  When you actually build the circuit, remember what I mentioned a few posts back regarding driving LEDs with the 6008.  You would need to re-wire the LED circuit from what I drew in the previous schematic.

[Filipe_Gomes]

could someone send me a picture that show me how to light a led with the ni usb 6008. I'm doing like the manual but the led don't turn on, this 5V on the picture of the manual is a external supply or the 5V of the 6008 board?

[Filipe_Gomes]

Anyone know how NI VISA in LabView works. I'm tring to read the data from a mutimeter. I need use a RS485-to-USB converter to plug it in the computer. And I want to use the LabView to get the data from the multmeter. I have already done a VI using the VISA and serial functions of the LabView but I cannot get the data. In my computer the USB device appears like a COM 4 port. The multmeter works with the MODBUS-RTU protocol and the multimeter has a technology called flexdata. It dosen't need to be in LabView, it can be C++, VisualBasic, or other language. I just need to get that data from the usb, because i want to update the informations on my VI, but i don't know how do i do that?

[Tom__Sedlack]

Filipe,

You would be better off starting a new thread in the appropriate group such as Instrument Control (GPIB, Serial, VISA, IVI) rather then in this discussion.  First, if somebody knows about NI VISA and not about the USB-6009, they would have no reason to look here to help you solve your question.  Also, if the original question has been answered, mark it a solved so others with the same question can go to the answer you used.  Lastly, and this is optional, it is common practice to thank the person that provided the answer by giving him a "Kudos".  It's like a pat on the back.

Tom

[uk4tech]

Dear Mr. Camell,

Can you give the model number of the opto isolator that you used? I have used all transistor, resistor, opto coupler combinations! I could make it run but for a short time only. These things failed when deployed on site. So, I need a reliable tested off the shelf component.

Thanks in advance.

Regards,

Karthik U.

[Camell]

I use Phoenix Contact 2944203. They are not cheap, but they can switch 24Vdc/1A and need only 4.2 mA input current (which has to be delivered by the NI digital output). And I can change the wiring quite fast instead of always soldering something 😉

Most of the other opto couplers need a higher input current (8-15mA) and can switch less current (100-200mA). I have made also tests with other opto couplers which need 10mA input current and they also worked (e.g. from Weidmueller).

My NI module 9403 can deliver max. 64mA for all digital outputs. That you have to keep in mind when using several opto couplers and other things.

If an opto coupler has only two inputs, you have to connect an digital output to input (+) and COM (of your NI digital card/module) to input (-).

If an opto coupler has three inputs, they are usually named Vcc, Gnd and TTL. Then you have to connect a digital output to Vcc which is always TRUE/HIGH (5V). To Gnd you have to connect NI's COM port. And to TTL you have to connect the digital port you want to use.