Frequently Asked Questions

RFC-1/B Latched Control Relays

The RFC-1 control relays provide a momentary contact when energized. The length of the contact closure is adjustable from 0.3 to 4.8 through a firmware setting. The setting is global–it effects both the raise and lower relays on all channels.

There is no built-in provision for latching relays on the RFC-1. The hardware architecture simply does not allow it.

Nevertheless, there are applications that require the use of a maintained contact. In those cases an outboard latching relay is suggested. Relay selection depends largely on the voltage and current requirements of the device to be controlled. There are literally hundreds if not thousands of variations.

Generally, an appropriate relay from any reputable manufacturer should work. It is impossible to suggest a specific relay that is appropriate for every installation. We can make a few suggestions to assist in the selection process.

The choice of control voltage, contact ratings and mounting options can be tailored to the application. The control voltage must be within the contact ratings of the RFC-1 control relays. These contacts are typically rated for 5A @ 30VDC. This should pose no significant limit on relay selection.

A dual-coil relay is easy to connect to the RFC-1/B and it is more intuitive to operate than a single-coil relay. With a dual-coil relay, one coil can be connected to the "raise/on" control relay of the RFC-1/B and the other can be connected to the "lower/off" control relay.

Single-coil relays sometimes require a polarity reversal to toggle the relay contacts. Additionally, a single-coil relay may toggle on and off using the using the same command from the RFC-1/B. This inconsistent behavior may lead to more frequent operator error.

Connections using a dual-coil relay are straight forward: use the common (COM) and normally open (NO) connections of two control relays on the RP-8 to switch a low voltage control signal–one control relay will operate each coil of the latching relay. Make the connections so that the latching relay operation is consistent with the on/off behavior of other channels so that operation is intuitive.