How can I interconnect two doorbells operating on different voltages?

i'm a noob/have rudimentary knowledge about batteries in series and parallel. i'll explain what i'm doing and would like your input as how to solve my problem.

i have 2 doorbells, one at the front of the house and one at the back.

please see attached photo of one doorbell to see how i've connected things up.

a 9v battery is attached to the black & red wires at the bottom. this doorbell uses the lower left & right terminals (at the top, where the white wires are) to connect to the push button. this forms one circuit.

then, the upper left & right terminals are connected to the other doorbell. that forms another circuit. that doorbell uses 4xAA batteries. so 6v.

as far as i can tell, both doorbells (batteries) are +ve to +ve.

so, first question: is this a series or parallel circuit?

what seems to be happening is that the 9v battery is draining/leaking because it becomes dead within a few weeks/months even if not used - ie not many people ringing the doorbell.

next question: how do i solve this 9v & 6v problem?

can i use a diode to stop the 9v battery leaking to the 6v one? how do i work out which diode i need to use?

or can it not be done? ie cannot make a 9v and a 6v parallel circuit work? (i'm assuming it is parallel).

or is there another way of configuring the wires so the 2 doorbells are separate? eg rather than using the upper terminals for the 2nd doorbell, i connect it directly to the push button? but then, the wires for both doorbells will be touching each other at the push button, and won't that also make a circuit and cause problems?

ok, over to you good people to give me the correct solution. thanks in advance.

the top circuit diagram shows the current and voltage if the first doorbell was by itself. the next circuit diagram shows the current and voltage if the second doorbell was by itself. however, I have the doorbells set up as in the last circuit diagram and there is a drain from the 9v battery into the 6v battery.

• A circuit diagram would be infinitely better than a photo. (You can add one by editing your post and clicking the circuit diagram button.) That being said, 9V batteries generally suck, and are especially unsuited for this type of use, because the solenoid will draw more current than the 9V battery can deliver in any efficient manner. You should be able to power the circuit from a single 4XAA battery if you wire the push buttons in parallel with each other and put them in series with the battery and the solenoid.
Dec 11 '17 at 11:20
• The first thing I saw was a out of focus picture, then two incidents of sloppiness in the first line, including the very first letter. That's where I stopped reading. Closing since now I don't know what is being asked, and -1 for thumbing your nose at all the volunteers here. Dec 11 '17 at 11:48
• why do you have two door bells?
– jsotola
Dec 11 '17 at 23:44
• install a relay in the 9V door bell. the relay would be operated by the 6V door bell. the contacts would be wired in parallel with the 9V door bell switch
– jsotola
Dec 11 '17 at 23:49
• the front doorbell cannot be heard at the back of the house. ok, thanks for your advice regarding the relay. i'll either take your advice about the relay or get another matching doorbell (either 6v one or 9v one).
– kamchow
Dec 12 '17 at 0:51

I agree with the other answer that it's very possible they'll both work on 6V or both work on 9V. If that is the case you could wire it so both doorbells are in parallel off one battery. There may be an issue if the battery doesn't have the power to run both doorbells.

You could use a relay as suggested in the comments. With the relay coil in parallel with the 9V doorbell, and the contacts switching the 6V doorbell, you'd be done. You'd just need a relay with the proper rating, and again the relay coil will take away a little of the power available to the 9V doorbell.

You could use surface mount DPST momentary switches for the doorbells, if you can find them, but you'd have to run four wires to the doorbell.

You could get a relay with two pole contacts and put another battery / power source in series with the doorbell switch in series with the relay coil, and have one set of contacts switch the back doorbell, and the other set switch the front doorbell.

You could install a PLC or home automation system that uses the doorbell as a digital input and the two doorbells as relay outputs, you could do all kinds of crazy things. You could get a dog that barks a lot or you could put up a sign that instructs people to knock really loudly.

Of course all these things are harder than just buying a system made for one switch and two chimes, which are readily available, but what fun would that be?

No matter what you do, you will have two batteries in parallel. You can only do that if they are the same voltage, which isn't the case here. The only thing you could try is if both bells would work on the same battery (either 6v or 9v) - if so, you could connect the bells in parallel to a single battery.

• from the little research i've been doing, i think you're correct. thanks for your reply.
– kamchow
Dec 11 '17 at 14:38
• @kamchow, please accept or upvote answers to show gratitude and resolve the question. Take the tour. Dec 18 '17 at 13:59
• isherwood - I accept the given solutions. I don't have the privilege to close this question. Please ask one of the moderators to do it for me. Thank you. Dec 19 '17 at 9:07
• Actually @jsotola 's comment above is correct, this can be solved using a relay, but first I would try the suggestion in this answer - see if they both work on 6V or 9V. Aug 10 '18 at 17:40