Controlling Multiple Loads with One Input: I/O Expanders

February 20, 2019
Tech Tuesday

Can you imagine what work would be like if we didn’t have memos or email lists? We would have to take the time to walk around our place of work and individually tell every person the new information. Depending on how many coworkers you have, that could take a very long time. It would be terribly inefficient. Now ask yourself, why are you doing exactly that with your Building Automation System?

Let me give an example. Let’s say you have four fans. They won’t leave you alone because you’re too popular. After you tell them to leave you alone, you realize you have four ceiling fans that you are exhausting to control. Sometimes you have them all off, sometimes you have them all on, nothing unusual there. However, sometimes you need only one on, or maybe two specific fans on and not the other two. Every time you want to change something, you have to individually give them commands from your controller.  Or even worse, you walk around the place and flip all the individual switches. 

You could continue take the time and effort to control each of them individually, or you can use one of our I/O expanders and achieve all of that with one signal. It’s kinda like sending out a group text to all your friends with info on your next hangout, except that everyone actually reads it and responds. This is done by having multiple relays that respond to different analog values at the input. As the voltage increases at the input, the relays respond in a “truth table” fashion. Take a look at the table for the RIBMN24Q2C:

The RIBMN24Q2C allows you to control two fans individually, with one analog control input. You can have both fans on, both fans off, or even specify which fan you want on. This concept is expanded to three and four relays with the RIBMN24Q3C and RIBMN24Q4C respectively. All three of these boards accept analog inputs for both 0-10V and 0-5V.

If you don’t like the “truth table” functionality, (you don’t want to go through every combination of loads being on or off before they’re finally all on, for example) or your analog control signal doesn’t operate on 0-10V or 0-5V,  try the RIBMN24Q4C-PX. This device allows you to program the voltage threshold that each relay activates at. You make your own table, so to speak.

Our I/O expanders can be used in a wide variety of applications to help improve efficiency and consolidate controls. So be creative with them, and be sure to give us a call at tech support if you have any questions.


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About the Author

Tym Moore is an Electrical Engineer who hails from the best state of Colorado.
He graduated from Colorado State University in 2017 and moved to Indiana shortly afterward to marry his now wife. Outside of work, Tym spends most of his time driving back home, and complaining about how flat Indiana is.

Be sure to give Tym a call for tech support. He will always do his best to find a solution for you.