The reason for the ac of course is that they know that many bells have a
pretty bad dc or ac supply going to them already. Inside there is a circuit
to rectify it and charge the battery, and the resistor is merely protection,
if slightly inefficient at charging batteries, as it will get warm. I've
seen this idea many times in the past on less techy door intercoms and the
like.
Brian

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"Tricky Dicky" wrote in message
...
On Monday, 23 November 2020 at 20:24:41 UTC, Ian Jackson wrote:
I want to buy a 'Ring' Doorbell (probably Ring 2) and the Ring 'Chime' -
and for initial simplicity I want to use it battery-powered. However, at
a later date I might want to change it to wired power.

There's loads of information on the web, but I find a lot of it rather
confusing (and even somewhat contradictory). Much of it sort-of avoids
quite telling you exactly what you want to know, and the fact that there
are so many different versions and models doesn't help matters.

I would have thought that an external power feed would be done by simply
by removing the battery pack, and feeding it with the appropriate DC
voltage. However, apparently that is not the way. Some websites say you
use an 18V AC supply connected directly to the screws inside the
doorbell - but the official Ring support site shows an 8 to 24VAC supply
feeding it via a 25 ohm, 50W (!!!) resistor [I not it also says 'Don't
use a diode' - so I guess when it says AC it really means it.]

Some sites do tell you that if you use an external power feed you have
to retain the battery. This is because the doorbell does not run
directly from the external power feed. Instead, it uses the battery as
its power source, while the battery is trickle charged from the external
feed.

So can anyone confirm that I have my facts right. Am I safe to buy a
Ring Doorbell 2 and a Chime, and will later be able to add an external
power feed?
--
Ian
Ring Doorbell 2 can be externally powered. Actually it works off the
battery the external power just provides a constant trickle charge. I
wired ours using the following charger

https://www.amazon.co.uk/Doorbell-Tr.../dp/B07ZNGDYK3

At the time the resistor was unavailable from ring so I got these half
price than the Ring version and you get two to boot if you consider a
second camera

https://www.amazon.co.uk/YiePhiot-Re.../dp/B07PFHLVW1.

Richard