A Mechanical Relay Conundrum

[James Sentman]

long thread with much data so sorry if I've missed things, but do I understand that your doorbell connects to a timed relay for running the chimes? And you're considering putting the button directly into XTension and let it turn on the chimes? That would certainly work but thats a lot of work for the doorbell.

Does the doorbell work just connected up normally to the button? I can't understand why a momentary connection on the button doesn't let it ring out it's entire chime sequence unless you're powering the power and not the trigger. One is not normally required to hold the button in until the sounds are finished are you?

Doorbells can be a bit tricky because of they way they used to work with the solenoid and a lighted button that passed a little current through but not enough to actually make the solenoid move and hit the physical bell. The electronic ones often mimic this so that you can have a lighted button so there will always be some current flowing through the wires and you can't just put a relay between them because they are a switch loop and not a dry contact or powered pair or something.

If the doorbell is just a solenoid or a series of solenoids that strike a physical chime then getting them into XTension is easy. Just use a DS10 and tape the reed switch to the solenoid. I've done that at 2 houses now. The magnetic pulse from the chime going off triggers the reed switch easily. You could also connect the reed switch to just about any other method to get it into XTension.

You should also be able to use an AC relay to get the switch, IF the switch isn't passing too much power through to light it's bulb. It doesn't normally take much power to turn on a relay so this might be tricky or might require a resistor inline with the relay to limit that. But, you can't just connect it across the 2 wires from the doorbell button. The doorbell circuit is 24v (or 16v if thats what I read in your emails) out one side and return on the other. So if you just put the relay across them it will just be on all the time and probably your doorbell going off all the time and thats not helpful ;) You need to find the switched leg of the doorbell wire and put the relay between that and the neutral of the 24 (or16) volt transformer. (assuming the switch leg is breaking the hot side and not the neutral, could be anything with a doorbell) that would probably work.

The powerflash would definitely work, but again I think you'll have to place it between the switched leg of the doorbell power and the neutral from the transformer rather than just across the switch leg. But this might also suffer from the same potential problem of too much current flowing through the bulb in the lighted button.

And then there are even more complicated solutions like putting the wire through a current sensing relay. They make those for building automation and there are some low power versions for arduino sensing that could be used to close a contact when the current passing through the sensor was above a certain point and use that to get your contact closure into XTension. This would work with a solenoid type doorbell as there is considerable current passing through to ring the bell, but I doubt that it would work with an electronic doorbell as the amount of current necessary to set it off would be very tiny.

The idea of putting the button directly into XTension and then letting XTension set off the bell bothers me a little because single point of failure. The one time you're expecting that package that you must sign for or it goes back you'll be in the closet with XTension and have just pulled the plug to do a system update or something and you'll miss it. 



On Sep 16, 2014, at 12:00 AM, George Handley <ghandley at kc.rr.com> wrote:

> You are correct in that I had completely forgotten about the PowerFlash module  as another tool, and I may end up trying that approach, but it might require completely redoing my little component box for the present 16v relay into something much larger to accommodate even an inline appliance module. Not impossible, not simple and elegant, but worthy of consideration.
> 
> The whole project has been frustrating, as the chime needs a good momentary contact to play it’s entire tune. If it has less than, that my relay shuts it off as soon as they release the button. No, the more I ponder what can go wrong with each idea, the more I realize I need that doorbell button to be a dry contact triggering a Weeder board point that I already have… or the PowerFlash, then write the scene and timing with XTension as I want it.
> 

Thanks,
 	James


James Sentman                       http://sentman.com		http://MacHomeAutomation.com