this should be a simple question, but no product pages seem to describe this situation. I want to hook up a wired doorbell with two buttons and two chime units. Both bells should respond to both buttons (i.e., one chime back door, two chime front door). However, my dad tried this years ago and the result was the transformer burned out. I'd like to try again. Can anyone tell how to build such a circuit properly?
Double Doorbell
doorbell
Related Solutions
Here is my suggestion of what you can do.
Go to good old eBay and purchase a kit that looks like this:
You can find these for very reasonable prices using a search string like "wireless remote control".
The fob is battery operated and activates a relay on the receiver board when the buttons are pressed. The particular model shown comes with a nice looking wall mountable plastic enclosure to cover the circuit board. (Do not mount the plastic box outside however).
Connecting into the existing doorbell is simple. Just access the wire pair between the door bell and the push button and splice in a new pair that will connect to the relay of the receiver box at the NO (normally open) and COM (common) contact points. This connection will allow the activated relay to act as a parallel button with the existing button with no modifications to the existing button.
The relay receiver box requires a 12VDC source to operate. This can be supplied from a surplus AC wall adapter that you could also purchase on eBay or visit your local GoodWill store where you can find a huge assortment of adapters. If you chose to mount the receiver in an attic or crawl space you could find an electrical junction box and mount an outlet cover plate on it to get a convenient place to plug in your 12V adapter.
You could mount the dongle out on the gate directly (the dongles I've used had a sealed inner liner inside the case that keeps moisture out of the inside electronics). What may be preferable is to modify the dongle with a wire pair soldered across one of the button contacts and then run those wires over to a more conventional style of doorbell button that you would mount on the gate. The hacked dongle could then be enclosed in a plastic hobby box that is sealed and then mounted to the exterior in an unobtrusive area while at the same time the plastic box letting the wireless RF signal come through the box and make its way to the relay receiver board. You will occasionally have to replace the dongle battery but they seem to last a year or more with moderate use.
I've used almost identical kits to replace my very old non-functional garage door openers with the relay module wired across the manual open/close buttons that are inside the garage. The dongle is then easily carried around or kept in the automobile.
I ended up buying two new doorbells with speakers instead of chimes. I was told by the manufacture that these will work on 16va. Plugged everything together and now it works.
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Best Answer
You don't need a relay and you don't need two transformers. You do need a transformer powerful enough to operate both chimes, so you can't buy doorbell kits with transformer included. You'll need to select the transformer separately.
You should purchase two identical chime units. If the chime units are different, their voltages must match. The transformer voltage must match the chime unit voltage, and the transformer amperage must equal the sum of the two chime unit amperages.
A single dual-tone chime is easy to wire up. Usually there are wiring diagrams in the package and sometimes they even make sense.
Select one low-voltage terminal on the transformer to be the supply leg and the other to be the return leg. It doesn't matter which because it's AC and isolated from your house mains. Connect the supply leg to both doorbell buttons. Connect the other terminal on the front door button to the ding-dong terminal on the chime, and the other terminal on the back door button to the ding terminal on the chime. Connect the common terminal on the chime to the return leg on the transformer.
Now, to wire two dual-tone chimes is almost as easy. You just connect the second chime unit to the first in parallel, ding-dong terminal to ding-dong terminal, ding to ding, and common to common.
This diagram has the transformer at the circuit breaker service panel, but you will probably put yours in your utility room. In any case, for safety reasons, please mount your transformer on a junction box.
The aqua ring indicates where all the wires come together in your utility room. Black indicates the low-voltage supply leg, and white the low-voltage return leg. Of course, the colors are in the diagram only; I'm not trying to suggest that you buy red and blue wire.