Doorbells in parallel

[kamchow]

(1) a big sorry to MJL. i emailed you with this problem. please please please ignore the email. i did not read the clear instructions on your contact page and wasted your time with my email. again, apologies.

ok, forum people, could one of you come to my rescue? yes, i'm a complete noob and need spoonfeeding! 

i have 2 doorbells. the doorbell pushbutton is connected to one doorbell in the normal way. the other doorbell is connected to the first doorbell via the same terminals that the pushbutton is connected to. the pushbutton operates both doorbells.

afaik, this is a parallel circuit and it works. press pushbutton and both doorbells chime.

here is the problem: first doorbell runs off a 9v battery and the second one runs off a 6v battery (4 x 1.5v).

when the pushbutton is pressed, for that split second the circuit is closed, does the 9v battery "flow" into the 6v battery?

even when the circuit is open (pushbutton not pressed), is anything happening in the circuit - between the doorbells?

i do not have any measuring instruments like a multimeter.
also, since these are cheap doorbells, i do not know the resistance of the doorbells.

another thing, say in the future i bought a multimeter, how would i go about measuring voltages and power consumption etc across various points in the circuit? it would be great if someone could post a video showing how to do this.

ok, over to you boffins to help me out. i thank you in advance.

[ProBang2]

The status "Pushbutton pressed" is not the problem. It is simply closing the circuit of each battery.

Connecting both plus and minus poles in parallel together has the following effect:
The 9V batterie tries to charge the 6V (4x1.5) batteries unless their potential will be equal. The 9V batterie drains, the 6V will be overloaded.

[kamchow]

ProBang2, thanks for your reply. i had a suspicion that would happen between the batteries.

tell me, would i have the same issue if both doorbells were connected to the pushbutton separately?
so, 2 separate circuits, both connected only at the pushbutton terminals.

but in the back of my mind, i think since both doorbells wires are physically touching each other (at the pushbutton terminals), so there is still a "circuit" and the 9v battery would still drain into the 6v battery. is that correct?

if that is the case, is the simple solution for me to get another 9v (or 6v) doorbell and then it doesn't matter whether the doorbells are in parallel or separate?

[SeanB]

That, or use 2 1N400x diodes to prevent reverse current flow. This really depends on the bell itself. The old one used a solenoid, with the bell push closing the circuit, while the newer ones are all electronic, and you simply are pulling a digital logic input low to trigger it. However a diode in series with the wire, such that it will be forward biased when the button is pressed, will isolate the 2 from each other, provided the common connection is actually connected to the negative terminal of the battery. If not you need 2 identical doorbells and connect like that.

[kamchow]

SeanB, thanks for your input. this is probably the route i'll take just so i can dabble a bit and hopefully learn a few things.

ok, i think this case is closed.

let me say, it is truly refreshing to find a forum where people answer questions in a straightforward manner and in a nice way. a tip of the hat to both of you gentleman.