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Ring Doorbell

Discussion in 'General Electronics Discussion' started by muzzzzy, Nov 2, 2016.

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  1. muzzzzy


    Nov 2, 2016
    Greetings all,
    Have a small issue as i have been asked to install a psu for a ring doorbell. The psu is fairly straightforward 8-24vax however it specifically asks for a wirewound resistor to be fitted in series.
    The Resistor apparently has to be a wirewound 25-30 ohm 20-50W.
    This resistor is not the most generally available and i was wondering what the purpose is in an AC circuit.

    Thanks for any information.
  2. Gryd3


    Jun 25, 2014
    We could guess, but ideally we would need more detail regarding the PSU you currently have.
    Also, is it asking to install the resistor in series with what component? PSU, button, or bell?
  3. muzzzzy


    Nov 2, 2016
    If you do plan to connect directly to a transformer and do not have a home doorbell, a resistor is REQUIRED in place of a mechanical or electronic doorbell kit for this alternate configuration to work successfully. Do NOT install a diode.


    This is all the information given but the resistors are not readily available which made me question what its for i guess it has something to do with the internal circuitry of the Ring unit.
  4. davenn

    davenn Moderator

    Sep 5, 2009
    yeah, Im not surprised they are not readily available ... that's totally crazy ...
    seriously, it would be easier to pick a much better product
  5. duke37


    Jan 9, 2011
    I do not understand why a wire wound resistor is mandatory.
    Resistors contained in an extruded aluminium tube which can be bolted to a heat sink are available.
  6. Bluejets


    Oct 5, 2014
    I think one would need to know more about what this " doorbell kit" comprises to give an educated answer. 2amps is some bell.
  7. Audioguru


    Sep 24, 2016
    The doorbell might use a high power motor to spin a hammer that strikes the gong as it rotates. Then maybe the motor draws a very high current when it starts and the resistor limits the current?
  8. muzzzzy


    Nov 2, 2016
    The ring unit that the psu supplies is a wifi product so has a push button and camera incorporated. When pushed the video and alert is activated on a smartphone app so you can see and talk to the caller wherever you are. Problem is i cant try the unit out because my customer has purchased it directly and wants me to hook it up to the appropriate supply. So the first time i would see it is when i turn up to do the job. Just wondered if it was obvious why the resistor was required so i could source an alternative product .... but thanks so far .
  9. AnalogKid


    Jun 10, 2015
    Those are wire-wound.

    Depending on the construction, wire-wound resistors can be much more survivable with high transient currents, or intentionally blow like a fuse (the 'fusistor'). Hollow core vitreous enamel parts are very rugged. Note that when operated continuously at 50% or more of their power rating, they get too hot to touch.

    The resistor probably is acting as a ballast to take some of the heat dissipation away from the onboard voltage regulator, but 20-50 W seems,,, conservative.

    Last edited: Nov 2, 2016
  10. Gryd3


    Jun 25, 2014
    Did a quick search to confirm some thoughts on this.
    If this device is intended to 'ring' a household door bell, then it's quite probable that the device will temporarily short itself out when the button is pushed.
    It's how home door-bells are installed. (In series)
    Transformer -> Button -> Bell -> Transformer.

    If you have no 'Bell' and you push the 'Button' or have another device emulate a button push, you will fry the PSU/transformer.
    If this device is meant to be 'retro-fit' to an existing system, the wire-round resistor is in place to protect the PSU and potentially the switching mechanism inside this 'smart' door-bell.

    This is what happens unfortunately when the client chooses their own device. If you can't get your hands on it first to approve charge them extra for the hassle to make it work!
    It most certainly seems like you need to either get your hands on a home door-bell, or buy a beefy resistor.

    The interesting thing here though, is that we have no details on how the device is powered... If we know the operating voltage and current of the device and it's behaviour we might be able to recommend a more exact value for the resistor, or even find a way to not use it!

    Keep in mind that my notes here are completely based on the perception that this device is sold to homes/residences that already have a door-bell installed... so this would be a drop-in replacement for an existing door-bell button.
    If this is indeed the case, a resistor of too high an Ω rating may limit the operating voltage/current of the door bell causing operating problems. A very small Ω value would be ideal in this case, but the Watt rating of the resistor needs to be much higher to handle the current. That said... the Ω rating can NOT be too small as to allow excessive current to be drawn from the PSU/transformer... the fact that the 'current' or 'power' rating is unknown right now makes the suggestion questionable.
  11. Jonnystuart


    Sep 16, 2017
    Hi. Did you get to the bottom of this?
  12. mathewjg


    Mar 29, 2018
    I am struggling with this same problem. The recommended resistor is 4" long and seems a bit ridiculous. An AC to AC mains adapter is recommended with 8 to 24 volts output. Current is not specified. On Amazon there are some simple AC/AC 18v 500mA adapters being sold as suitable for direct connection to the ring 2. I do get the point that a short might be occurring when the door bell is pushed but 50 Watts seems excessive.
  13. KMoffett


    Jan 21, 2009
    From watching the online videos, what the OP is trying to do is use a bell transformer to power the RING unit, but with no "dorbell" in the house. With no existing dorbell the RING unit runs on batteries. The resistor would simulate an electromechanical chime. Hooking the transformer directly to the RING contacts would short out the transformed when activated. I think.

  14. mathewjg


    Mar 29, 2018
    I just put a meter across the ring 2 terminals. It stays very high resistance when the bell button is pushed so I am not sure what's going on! it would be handy to see a circuit diagram of the ring 2. I have found some physically smaller resistors on eBay so I suppose just go with the manufacturers recommendation
  15. Retired Engineer

    Retired Engineer

    Apr 19, 2018
    Comment: "Otherwise known as up a well known creek without a paddle."
  16. Steverabs


    Sep 3, 2018
    Assuming the bell switch is electronic or a relay with low on resistance when forward biased the resistor wattage will vary according to the transformer voltage selected. So assuming likely rms voltages of 8 V, 12 V, 16 V and 24 V, the following dissipations (Rounded up) would be seen in a 25 Ohm and 33 Ohm resistors:

    24 V....... 25 Ohm = 24 Watts, 33 Ohm = 18 Watts
    16 V....... 25 Ohm = 11 Watts, 33 Ohm = 8 Watts
    12 V....... 25 Ohm = 6 Watts, 33 Ohm = 5 Watts
    8 V......... 25 Ohm = 3 Watts, 33 Ohm = 2 Watts

    RING have rounded the Power dissipation ratings up to industry standard values, ie. 2 Watt and 50 Watt, hence the huge discrepancy between 24 Watts absolute tops calculated and 50 Watts recommended. Of course even with the figures I've calculated, you'll only get the resistors up to the maximum case temperature if you keep the button pressed continuously which obviously won't happen. So, if RING suggest 8V as the lowest voltage we really only need to use a 2 Watt 33 Ohm resistor, likewise if you only have a 24 V output from your transformer, then you only really need a 25 Watt 25 Ohm resistor.

    One other thing to remember. Round axial leaded resistors (leads either end) are specified in free air and usually between 25 deg C and 70 deg C. So if your resistor is exposed and is not in an enclosed or insulated box then the power ratings I calculated are correct. If encapsulated, then you'll possibly have to increase the rating. Panel mount resistors dissipate their heat from the base to the mouning panel. So if the Panel is large and at 25 deg C the rating is correct, but if the panel is warm or you aren't bolting it down you'll again have to derate the resistor (Increase the max dissipation figure).
  17. Demonjrw


    Jun 3, 2020
    so what resistor do I need as no one seems to have give answers.
  18. AnalogKid


    Jun 10, 2015
    This thread is over three years old. Better to start your own thread with the details of your particular question.

  19. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    @Demonjrw: The thread starter, @muzzzzy joined EP on Nov 2, 2016, made three posts the same date, and has not appeared here since. This was a drive-by poster looking only for a quick answer, not a dialog. If you are having a similar problem installing a Ring video doorbell, please create another thread as @AnalogKid suggested. Please don't be a drive-by poster. And welcome to ElectronicsPoint.
    narkeleptk likes this.
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