Today’s Tech: Versatility of Dry Contact Input RIB® Relays
I consider frogs to be rather intelligent creatures. Ask one how to activate a flood light when a garage door opens, and it will respond “RIB-it.” Ask another how to activate a damper when a hood fan is energized, and yet again, the response is “RIB-it.” Seems we could learn a thing or two - even from a frog! If there is a specific family of RIB® devices that a frog is referring to, I’d like to think it is the dry contact input line of relays. These devices have proven to be quite versatile in the field, and I find myself suggesting them for many different applications. If you recall my last blog post discussing the application of a RIB21CDC with a RIBXGA current sensor to control a motorized projector screen, the way those two devices were used was quite unique. In this post, I want to focus on the entire line of dry contact input RIB® relays, highlighting the different versions and benefits of using this type of device.
The Dry Contact Input
What makes the dry contact input relay different from some of our other standard RIB® relay devices? Typically, the coils on the standard line of RIB® relays are energized as soon as the appropriate power is present at the coil input wires or terminals. However, with the dry contact input relays, the coil input voltage applied to the device also powers the internal control circuitry. That control circuitry is governed by the status of the dry contact input wires (White/Red and White/Blue pair of wires) or terminals. An open circuit between said wires or terminals means no power to the relay coil (Normally Open is open) and a closed circuit or “short” between said wires or terminals means power to the relay coil (Normally Open is now closed).
The dry contact input has a Class 2 signal that passes through once the wires or terminals are shorted together. This signal may extend out for thousands of feet before a loss in signal strength is seen. Any kind of dry contact output (i.e. relay output, switch, push button, limit switch, thermostat, or one of our current sensors) may be used to control the status of the dry contact input – just be sure there is no power present at the device doing the switching!
Choice of Input Voltage and Relay Size
Our family of dry contact input relays comes in a variety of options for input voltage. The input voltage designation may be found within the model name of the device, “01” being 120 Vac input voltage and “02” being any value between 208-277 Vac input voltage. The power to energize the control circuitry may be brought to the relay on a separate pair of wires or may be a local power source near the relay. As for the relay within the device, there are four options:
- 10 Amp, SPDT relay
- 20 Amp, SPDT relay
- 30 Amp, DPDT relay
- 30 Amp, 3PDT relay
* Please note that the list above gives Amp ratings for a resistive load. Refer to the device datasheets on our website for a full listing of the contact ratings.
Choice of Device Operation
Within the family of dry contact input RIB® relays, there are options to control the way the device operates. To start out, you may add an override switch RIB01SBDC or RIB02SBDC) that can be used to switch the load on or off regardless of the status of the dry contact input wires. This option reduces the relay’s contacts to just the normally open for wiring. Want access to the normally closed? Well, consider adding a “-NC” to the end of the model name or you could use either the RIB01SBCDC or the RIB02SBCDC, both of which provide access to the normally closed and normally open relay contacts. Finally, do you want a time delay function for the device? We have that, too! There are “delay on make” and “delay on break” options to choose from (RIBD01BDC or RIBD01BDC-DOB). Of course, those are available in 120 Vac or 208-277 Vac input options as well.
The Choice is Yours
Whether wiring up a limit switch to stop the flow of water into a tank or activating the trap door under your welcome mat when that salesman rings the door bell, I would heed the advice from the wise old frog: RIB-it! The RIB21CDC makes for a great utility truck relay, considering its 120 Vac to 277 Vac acceptance. You can even permanently short together the dry contact input wires or terminals to get the device to act as a normal relay when the input power is applied or taken away. Whatever you do, though, practice safe installation procedures for our device and don’t blame us for the injured door-to-door salesman!