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Thread: Doorbell wiring

  1. #21
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    Quote Originally Posted by LarryFine View Post
    That diode is there to allow electronic door chimes to complete the programmed music after the button is released.
    Oh that makes sense. Thanks!

  2. #22
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    Quote Originally Posted by LarryFine View Post
    That diode is there to allow electronic door chimes to complete the programmed music after the button is released.

    You should read zero volts across a doorbell button when it's being pushed.

    Again, the voltage you're reading across the un-pushed button is in series with the door chime.
    So you think I'll have a problem when installing the Ring Pro in regarding to sufficient voltage to start the unit? Ring says they need 16V, but the transformer is only rated for 16V and the chime will need some power so I think I need to upgrade the transformer right? To maybe a 24V unit?

  3. #23
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    Quote Originally Posted by petersonra View Post
    No idea what that is supposed to do.

    However look at this youtube video

    https://www.youtube.com/watch?v=3vaGGiJrE2k
    The link was very helpful thanks!

  4. #24
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    Quote Originally Posted by minesh21 View Post
    So you think I'll have a problem when installing the Ring Pro in regarding to sufficient voltage to start the unit? Ring says they need 16V, but the transformer is only rated for 16V and the chime will need some power so I think I need to upgrade the transformer right? To maybe a 24V unit?
    No, I believe it will work fine. I have installed a few, and have had no issues.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  5. #25
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    Quote Originally Posted by minesh21 View Post
    I can do without your judgements and attitude. I stopped reading after your opening statement. Try working on your people skills and maybe people will listen to what you have to say.
    Oh my! You should have read the rest.
    Following is just observation, not criticism.

    If you can actually tell the difference between a diode and a resistor and text with the photos was a typo, the details given in gar's post would tell you exactly why you measured what you did - esp as you were measuring across a diode.

    BTW, my youngest son AND his wife both have EE degrees from UW and son also has computer science degree - lots of $$ income from digital work. Someitimes in discussions with them on some aerospace power problems I've encountered I'm amazed at some of the analog and power knowledge they are missing. You seem to be missing the same type .. makes one wonder what other basic universities leave out to cram in all the digital information.

    Please go back and read the rest of gar's post to educate yourself.

  6. #26
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    I'm pretty sure that you cannot just read the voltage across the two terminals on the push button switch because it is in series with the chime (load). You need to depress the switch and read the voltage across the chime terminals.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  7. #27
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    Quote Originally Posted by minesh21 View Post
    So you think I'll have a problem when installing the Ring Pro in regarding to sufficient voltage to start the unit? Ring says they need 16V, but the transformer is only rated for 16V and the chime will need some power so I think I need to upgrade the transformer right? To maybe a 24V unit?
    I had one job where I needed to install a 30va transformer for the Ring to work.

  8. #28
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    Quote Originally Posted by minesh21 View Post
    The button wasn't depressed but I think it's the resistor that they placed in series at the button.
    Quote Originally Posted by petersonra View Post
    Not a resistor. Is a diode.
    Quote Originally Posted by minesh21 View Post
    Whoops. Thanks for the clarification. But that looks like it was added separately. Can you tell me what its use is for in this situation?
    It it parallel across the button switch.

    In a state of rest the diode is a half wave rectifier - pulsing DC is returning to your controller, and probably is what your measured 14 volts was, try switching your meter to DC and see what it says. Pressing button will shunt across the diode and full wave AC will return to your controller.

    Can't say I know any more about how your controller works, but apparently that AC signal starts the ring process, and possibly presence of the pulsing DC signal allows the programmed ring cycle to continue. Maybe if you took the diode off, you would have to press and hold the button to keep the chime playing.

    Haven't dealt with many electronic chimes. But for the typical solenoid type chimes - 16v is the typical nominal voltage. Many are wired with 18, 20 or even 22 AWG conductor, has to be some voltage drop in those - especially when the solenoid is pulling in, but at same time they are not designed to be anything but a brief load and coils burn up easily (solenoid or transformer) if the switch is closed for too long.
    I live for today, I'm just a day behind.

  9. #29
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    180505-1253 EDT

    minesh21:

    I ran some experimentx on two different small transformers.

    The first one is a 1958 or 1959 Nutone Inc., 24 V, Chime Transformer, Cap 20 VA, Made in USA, UL. No other information. One assumes 120 V input, but still might have been 117, not likely 115, and by this time not 110. The EI core on the outside reads 2.63" x 2.21" x 0.94".

    57.2 ohms is primary DC rrsistance.
    3.0 ohms is secondary DC resistance. 62.1 is estimatre of secondary reflected to primary. Thus, 119 ohms is total seen at primary with secondary shorted. A close comparison with 127 below. But there needs to be some additional equivalent resistance added for core loss power.

    Using a Kill-A-Watt EZ and a Fluke 27 the measurements were:

    Open secondary with no load,
    119.8 V, 0.02 A, 1.4 W, 2.6 VA, 0.53 PF, secondary 26.4 V.

    Shorted secondary with reduced input voltage. 70 V is about lowest with EZ.
    70.0 V, 0.55 A, 38 W, 38 VA, 1.00 PF. Apparrent input resistance 127 ohms.

    With nominal 120 V input and various secondary loads:
    57.5 ohms ---
    119.7 V, 0.10 A, 12.2 W, 12.2 VA, 1.00 PF, secondary 24.0 V.
    ............... --- load power 10.0 W, eff is 82%.
    ............... --- Approx source impedance of sec 2.6/(24/57.5) = 6.2 ohms.

    26.5 ohms ---
    120.7 V, 0.20 A, 24.4 W, 24.4 VA, 1.00 PF, secondary 21.5 V.
    ............... --- load power 17.4 W, eff is 71%.
    ............... --- Approx source impedance of sec 4.9/(21.5/26.5) = 6.04 ohms.

    With an estimated turns ratio of 4.55 the approx secondary source impedance of 6.04 reflects to the primary as 6.04*4.55*4.55 = 125 ohms. We seem to have fairly good corrrelations.

    What is apparent is that this transformer has been designed with a high internal resistance compared to its leakage inductance. Besides the PF of 1 showing on the Kill-A-Watt EZ scope traces show current and voltage very close to in phase.

    My expectation was that a current limiting transformer would have been designed with a high leakage inductance to resistance ratio. This Nutone was obviously not.

    I will get back to data on the other transfotmer later. It is designed for rectifier power supplies, and does show substantial leakage inductancre compared to its winding resistance. It is a newer transformer and has less iron and lower resistance, but its VA is higher at 30.

    The transformer of post #1 appears to have a large internal impedance, and for current limiting that is what you want.

    .

  10. #30
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    Nobody use wireless doorbells here? Mine cost around the equivalent of $10 or less. If they fail, other than for battery replacement, I'd just check 'em in the bin.
    Si hoc legere scis nimium eruditionis habes.

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