24 VDC vs 115 VAC sinking input signals

niswonger

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Join Date
Aug 2020
Location
Michigan
Posts
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Intern here, I have been tasked with setting up a 24V Keyence vision system. Looking at the control prints, the existing input signals are sinking to the I/O card come from 115 VAC devices (it's an AB 1769 IA16 input module).

I wanted to make sure that the input signals from the 24V device will work with the input card? Or do I need to use a relay?
 
Last edited:
The 1769-IA16 is a 120V input module. You would need a 24V input module such as the IQ16. Depending on number of inputs involved it may be simpler/cheaper to just use interposing relay(s) instead of getting a whole new input card.
 
You may already know this, but for the most part (unless you have no space or the rack is at maximum capacity), you can just snap another 1769 series card at the end of the existing rack. Therefore, I would recommend purchasing the 24VDC sinking input card that would accomodate the inputs rather than going through relays.
 
Yes , an interposing relay is required. Another option is to add an input module that accepts 24v sinking inputs. The second is preferred. Relays introduce more failure points - loose connections, welded contacts etc. If you choose the relay route, get ones with an integrated LED that energizes with the relay coil. Your maintenance staff will thank you.
 
+1 for using a sinking input card.
I would not use an interface relay because there is a small lag in energizing the relay and contact closures. there is also the possibility of the relay contacts chattering when they close.
I would also double check the Keyence requirements versus the input card requirements, you need to order the correct card.
james
 

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