"RING" Video Bell -- Why does it need a Resistive or Inductive Load to operate?

[Drobo]

I bought a RING video doorbell about 2 years ago and it works pretty well .  The installation assumed there was a 10-24vac chime already in use, and the installation provided a diode across the AC input for the RING doorbell that gets wired in parallel to the old chime doorbell.  My old doorbell transformer was putting out 20 vac and this setup worked fine until my 20+ year old chime literally smoked (very stinky) and stopped working.  I disconnected the old chime and from the AC transformer in the basement and it was still putting out 20vac so I left the RING connected but it would not charge.  I spoke to RING who said without the chime transformer, I needed to remove the diode on the RING AC input and place a 25 ohm 50W resistor in series.

Can someone explain to me why this is needed?

Jerry

[thm_w]

Schematics of what he's talking about if anyone is wondering:

https://support.ring.com/hc/en-us/articles/205180710-How-to-Connect-Your-Ring-Video-Doorbell-Directly-to-a-Low-Voltage-Transformer-Without-a-Pre-existing-Doorbell-
https://fccid.io/2AEUPBHARG031/User-Manual/User-manual-2875778

https://www.exploitee.rs/index.php/Ring_Doorbell
https://www.ifixit.com/Device/Ring_Video_Doorbell_Pro

I can't really see the power circuitry inside from any of the photos. They say AC input only so maybe there is a small low resistance transformer inside, that is why a resistor is required?

[Drobo]

The RING has an internal lithium battery and charging circuit.  Is it possible that the RING requires a specific range of current draw that the external resistor provides (20vac/25 ohm = 0.8A).  I spoke to RING tech support and they are clueless.  Also this resistor will draw 16W continuously 24x7... a doorbell chime only uses power when the button is pressed.  Isn't this a bit weird?

[thm_w]

The RING has an internal lithium battery and charging circuit.  Is it possible that the RING requires a specific range of current draw that the external resistor provides (20vac/25 ohm = 0.8A).  I spoke to RING tech support and they are clueless.  Also this resistor will draw 16W continuously 24x7... a doorbell chime only uses power when the button is pressed.  Isn't this a bit weird?

Oh good point, for some reason I was thinking there was still a N/O switch in the loop, but that is of course on the Ring unit itself..

Now it makes a bit more sense. When the resistor is installed, you can't have the diode as well or too much DC current would flow continuously.

What I'm thinking still is there is a small high resistance transformer inside the Ring unit, and it shorts that out to run more current through the chime and actuate it.
So it is possible that the unit may not draw the full 16W (you could measure it), and it only requires that resistor to prevent too much current flow when the internal transformer is shorted. The unit may be too "dumb" to know if there is a series chime installed or not, so resistor is a simple fix. The resistor value is not necessarily determining how much current is flowing, only the maximum.

The fact that they spec a 50W resistor is a bit scary though.