SLC Triac Output card... output shorted on.

AutomationTechBrian

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• Sep 3, 2019

• #1

Just looking to learn something today.... My understanding is that an output shorting on a SLC Triac card is a pretty standard card failure, with the remedy being replacement. But since this will be my first service call with that issue, I thought I'd take a moment and confirm. Is there anything else notable with those cards? Any known issues?

 

geniusintraining

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• Sep 3, 2019

• #2

AutomationTechBrian said:

I thought I'd take a moment and confirm. Is there anything else notable with those cards? Any known issues?

Click to expand...

Seen it a couple of times and its the norm... I dont know of any other issues with them but when building/designing a system its good to keep in mind from the safety side

 

AutomationTechBrian

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• Sep 3, 2019

• #3

I have a few minutes before I need to leave, so I did a quick search on the board. I hear mention about Triacs leaking, and I'm trying to figure out if this is where I should try using a pull-down resistor first.

I guess I'll need to measure the current first before choosing a resistor.

 

jaden

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• Sep 3, 2019

• #4

The old standard for a triac load on 120 VAC is 10K ohm, 2 Watt.

 

AutomationTechBrian

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• Sep 3, 2019

• #5

I'm thinking about the card, and how to install the resistor. Do I just put the resistor in series, hooking up one end to the wire, and the other end to the output terminal?

 

blftech

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• Sep 3, 2019

• #6

Triacs with no load can appear to be turned on. Once a load is applied the voltage should drop to zero.

 

James Mcquade

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• Sep 3, 2019

• #7

triacs will bite you if you are not careful..

my boss had a sq, d wiggy and his tester showed the outputs off.
when I unwired the output, I got lit up.

I used my fluke 87 and the outputs were on.
if memory server me correctly, you need a 25ma. load on the output for pull down current. but that's from my plc2 days.

james