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NI-9472 control of current output

Hello everyone

 

I'm with a problem in my NI-9472 that doesn't trigger a relay of 24V in DO1 or DO2, but it trigger well in DO6 and DO7.

To explain my cRIO 9076 have an application to monitor the voltage in train lines with a NI-9215 to acquire voltage in Channel 0 and Channel 1. Then i have a setup to trigger DO1 or DO2 if the voltage exceed a trigger in this cases, although i have DO6 and DO7 settled to signal warnings and watchdog, in this two cases the relays are ok, but in the DO1 or DO2 when i have the relay connected, the voltage is very low and the led in the card has a very low green light, i've measured the current and it's about 0,0001 A in DO1 or DO2 when active and 0,010 in DO6 and DO7. Any idea why this behaviour?

André Simões
Work with LV2019 and cRIO since 2021
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Hi Simon,

 


@Simon_A wrote:

although i have DO6 and DO7 settled to signal warnings and watchdog, in this two cases the relays are ok, but in the DO1 or DO2 when i have the relay connected, the voltage is very low and the led in the card has a very low green light, i've measured the current and it's about 0,0001 A in DO1 or DO2 when active and 0,010 in DO6 and DO7. Any idea why this behaviour?


You surely read the specs (there's a paragraph on tripping)!?

 

You can test those channels by measuring their ON/OFF resistance with a DMM between Vsup and Dx (without power supply connected to Vsup). What do you measure for all the channels?

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Hello GerdW

 

Thanks by your answer.

When i mean trip is not trip of the module, i want to put a signal on the external relay to activate a trip in the substation.

 

When i measure Dx with come i have 3,4 Mohm

André Simões
Work with LV2019 and cRIO since 2021
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Actually sounds like you blew up those channels. Did you connect the relay directly to the output without any flyback diode?

IUn5v.png

 

A relay is an inductive load that stores quite a bit of energy and that energy wants to go somewhere when you disrupt the current. Without anywhere to go it can generate a pretty high voltage that will easily breakdown typical semiconductor switches.

 

Those channels should be able to deliver 750 mA max, although there is also a maximum dissipation for all channels together. Your working relay seems to draw 10mA, but if you haven't done so yet, add this diode ASAP!

Rolf Kalbermatter
My Blog
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Hello Rolfk, thanks by your time and answer.

 

The relays that are in use have a diode internally so i think this is not the problem, but i find something that intrigates myself.

 

This is the FPGA code that control de inputs and outputs:

 

Simon_A_0-1691656215617.png 

Simon_A_1-1691656324791.png

 

I think that this pulse time on and off need to be the same or more frequent, when i've tested with pulse times of 10000ms in both the green led for DO1 or DO2 are similar to the others. I made a quick test based on the code for the DO7 which is a bit different.

 

Simon_A_2-1691656573076.png

 

But now when i'm deploying the new FPGA code it runs in RT with the old values of pulse time on and off. Do i need to format the crio to put a new configuration? It's better to change that pulse times to a constant?

 

Thanks by your time and help, you two are always here to help!

 

 

André Simões
Work with LV2019 and cRIO since 2021
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