9477

[bunnybunnito]

Greetings,

I am a newbie, so bare with me.

A want to control a few solid state relays (i.e. be at liberty to specify for the length of time that they are open and closed).

To control the SSR I am using a NI cDAQ-9174 with a NI 9477 and a 9 V battery.

As far as I know I have wired everything according to the diagram that is shown on the 9477 module’s side. What is perplexing is that the SSR LED is always on. It is as though the DO, by default, is open (HIGH).

Furthermore, in Measurements and Automation, when I create a task (Create Task/Generate Signals/DigitalOutput/LineOutput) and change the line’s polarity the LED remains on. I did a Self Test and Reset without there being an issue. I also went into the Test Panel and set all of the lines to LOW.

I attached a photo and to be clear the battery's positive is attached to the SSR's positive.

Perhaps someone knows what I am doing wrong. This will have to be resolved before I try to control timing.

Thanks in advance,

Bunny

[LDob]

Hi Bunny,

How does this question relate to real-time measurement and control? As far as I can tell from the hardware you mentioned, the cDAQ-9174 does not run embedded real-time. 

As for your question, have you tried different DO pins or only one? At this point my thoughts are that either the wiring still needs to be changed or the DO pin might be broken. It would be good to test the different DO pins individually without the SSR wired to it to make sure that you see consistent results and it's not just one pin that isn't working. 

Also, it's difficult to see how the wiring is set up based off of the picture that you attached. If you could create a wiring diagram that represents your system and attach that, it may help more.

Thanks,

Lauren

Applications Engineer

National Instruments

[bunnybunnito]

I'm trying to control several SSRs in real time.  Perhaps we have different definitions of real-time.  Please advise me where I should be posting my inquiries.

I checked the pins.  There, at least, is continuity through the female pins I am using.  Perhaps there is a short within the module.  I will solder a couple more and see if I get a different result.   I am assuming that the DO is normally in the off position.  

Sketch is attached.

Bunny

[bunnybunnito · Accepted solution]

It was a rogue pin (facepalm).

Bunny

[LDob]

Hi Bunny,

Thanks for letting us know, I'm glad you figured it out! 

Real-time operating systems are designed to run applications with very precise timing and a high degree of reliability. The operating system used must have a known maximum time for each critical operation that it performs in order to be considered real-time. 

For future questions about the NI 9477, I would recommend posting on the Multifunction DAQ forum.

Thanks,

Lauren

Applications Engineer

National Instruments