Powering RING video doorbells


In the last few months, Digi-Key has been receiving a fair number of calls from folks asking for resistors and/or transformers for use with ring brand video doorbells, and it seems likely that many are finding DK through this page on the support.ring.com site.

There, the FSOT30-25-ND
and FVT50-25-ND

are recommended by the ring product team for use with their equipment, and folks have been asking about the difference between the two.

Both are within ring’s recommended window of 25~33 ohms resistance, and 20~50W power rating. The FSOT30-25-ND measures roughly 1.25" x 1" x 0.6" and has some fairly convenient mounting holes, whereas the FVT50-25-ND is rather more cumbersome at 0.56" diam x 4" length. For the simple reason of physical convenience, the FSOT30-25-ND is likely the better choice between these two.

A related question along these lines is “Where can I get a suitable transformer?” All of these fall within the recommended output voltage range of 8~24VAC and come in a convenient plug-in form factor. Among them, the HM1574-ND would probably be a good first choice, as it lands nicely in the middle of the recommended voltage range and ties with several others in the group for lowest list price.


In follow-up, some have asked “Why the resistor?”

Please note that Ring requires this resistor only when a traditional bell/chime device is NOT being used:

While I’ve yet to reverse-engineer one, it would appear that the Ring doorbells are designed to be able to function as a direct replacement for a traditional doorbell switch, which simply connects two wires together when pressed.

The recommended resistor is intended to act as a substitute in place of a traditional chime/bell mechanism in this case; without it, Bad Things would be expected to happen to the Ring device and/or the installation the first time somebody rang the bell.

Though on a much smaller scale, omitting the resistor without using a traditional bell/chime would be akin to cutting the cord off one’s toaster, twisting the conductors in the cord together, and plugging the cord into a live outlet. A stout spark and a tripped breaker/blown fuse is about the least unpleasant outcome one can expect from doing that… Similarly, omitting the recommended resistor when required is likely to cause permanent damage to one’s new $200 doorbell.


There is a setting in the doorbell app where you can tell it whether there’s a doorbell or not, and if there is whether it’s a mechanical or digital type. If you configure your Ring to not have a doorbell, then in principle the resistor is not required. But it’s probably good practice in case of misconfiguration or software error.