I finally had a chance to get a Ring Pro, and needed to connect it directly to a transformer. Thanks for this great discussion. There seems to be some mystery to why this is all happening. I’m an electrical engineer, so have insight into this, but am not an expert on these devices. I can describe the issue and some options…
The Ring doorbell devices were designed to be spliced into the loop of a standard doorbell circuit. The Ring must not only do its fancy work, but also act like the switch you replaced so it rings the doorbell. When you use it this way, there is another load in that loop, the doorbell solenoid. That’s the thing that moves the striker to ring the bell. So when you push the button in this normal installation, the switch is shorting out the circuit to some extent in order to ring the bell.
Now… when you connect the Ring Pro directly to a transformer with no bell, you’re shorting out the whole regular transformer with no load in the circuit… bad idea. High current flows in the wire, transformer, and your Ring Pro… which might damage things eventually.
So, this is why the above solutions include a 25 ohm (wire wound) 50 watt resistor in the loop with the transformer and Ring Pro. This acts like a “dummy load” replacing the doorbell. When the button is pushed, the current is limited. The reason the resistor needs to be 50 watts and wire-wound is to keep it from getting too hot should the button be closed for long periods.
Ring also has a couple other solutions for this. One is that they include a Ring Pro Power Kit to help with a couple situations. Situation 1: It is used to jump across the doorbell to get extra power to the Ring Pro. In our case (just a transformer) this is useless. Situation 2: If you look at the instructions online for transformer-only, you will see you can remove the sticker on the device and get to a second set of connections called “Bypass Mode” … which is pretty much exactly like putting the 25 ohm resistor in the loop with the transformer and Ring Pro… it acts like a dummy load. So, you already have what you need in the Ring Pro box to do what you need to install the Ring Pro with transformer only! You can find this instruction in the Ring Pro wiring diagrams for transformer-only use.
What’s inside this Power Pro Kit are more sophisticated devices we don’t need to understand here. I opened up mine out of curiosity and this is what it looks like. The smaller square connector is for Situation 1, and the larger connector is for Situation 2… the bypass mode.
There is another simpler solution, purchase the Ring Plug-In Adapter For Video Doorbell Pro, which costs $29 each and has a long wire on it with terminals. This plugs into an outlet and connects directly to the Ring Pro. Although the gentleman’s 4-doorbell project was fun and impressive, I bet buying four of these would be way easier. What is this? This is a plug-in transformer with a built in “dummy load” that most transformers do not have… so you don’t have to purchase anything else. Way simpler, although less impressive.
But… don’t forget, when you use a transformer-only installation, you don’t hear anything when the doorbell button is pressed! That’s another issue to solve.