Why would a wireround resistor be needed like with this CAMERA doorbell?

[MrMobodies]

As ambiguous as that statement about requring the 30va power supply in a thread I just started.
https://www.eevblog.com/forum/chat/conflicting-va-information-about-hardwiring-door-bell-on-eufy-websiie/

I Just saw a couple of videos with Youtubers and DIY'ers installing these things recommending to use wireround resistors on this Eufi one (not in the eufi manual) and others, Ring it does) and even searching but can not seem to find the reason WHY.

Here it mentions one in the wiring diagram for a RING doorbell camera.

No reason why without it.

Nothing on the page on the EUFI about requring one
https://support.eufy.com/s/article/How-to-Hardwire-Your-eufy-Wired-Doorbell-without-an-Existing-Wires

Nothing in the manual for Eufi:
https://ankertechnologycompanyltd.my.salesforce.com/sfc/dist/version/download/?oid=00D5g000004DkWQ&ids=0685g000007fnOnAAI&d=/a/5g000000gHI7/.As1GV_d9jcdpQJySXTTjRP4E8y.ibYvpAVsXB6hQ9g&operationContext=DELIVERY&asPdf=true&viewId=05HJ1000001qy13MAA&dpt=

But a Youtube video of someone putting one of these on a Eufi despite it not being required in the manual or website:

3.04 and also i'll be adding a resistor
3:10 this resistor is a 50 watt 24
3:13 25 ohm resistor so
3:16 this will go on to
3:21 either 8 or 24 volts
3:25 so each end will go

Comment:

@mkzayar1836 2 years ago 11 thumbs up
I don't understand fully. Why do you need the resistor for ?

No reply


3:37 in the video

The wiring must be connected to a transformer
with a voltage of 8VAC - 24VAC
and an internal doorbell or resistor.

2.05 in the video

So what are you going to need the resistor.

Very frustrating seeing in the comments, in other videos "oh get one", "I got one", "this is what I need and it was very helpful" etc but NOT WHY.

Can someone PLEASE explain whether or why this would need a resistor and what it does as to opposed without.

Thanks

OOps title edit: wirefound resistor NOT fuse. another mistake with the title. CAMERA doorbell.
Sorry about this.

[shabaz]

Usually the information is pretty vague because the manufacturers hope people use installers rather than do it themselves, and probably the installers might information-hide.

At least from Ring doorbell usage (I can't comment on Eufy, but it might be fairly similar) the resistor was only needed on older doorbells.
On newer doorbells, it's not needed. Nevertheless, I went for the topology where it's powered through a solenoid (i.e. the solenoid inside mechanical door chimes), so there is a bit of resistance in effect. It sips power, just enough to keep it's internal battery topped up, and that small amount of power doesn't energise the solenoid. The Ring doorbell is designed to act like a short across its power terminals (well, close to a short; I imagine it current-limits) when the user presses the button, so that the mechanical chime can work too. Presumably the older doorbells couldn't do that, so they would have to have a resistor if there was no solenoid in series.

I can recommend these parts for a Ring doorbell (specifically the "Ring Video Doorbell 4") because it's been in use for 3 years, with no issue so far.
I used a Friedland E3539N transformer, rated at 12V, and you'll see about 22 V AC on the output with a multimeter, and wired the Ring doorbell, and a mechanical (i.e. solenoid) door chime (Honeywell "Ding Dong D117") both in series. That works great.

If your doorbell requires a similar voltage and has an internal battery, then there may be a good chance that the items mentioned will work for you.

[Kim Christensen]

If the video doorbell is designed to replace the button and ring the original bell, it needs the resistance of the old bell in the circuit. So if the old bell as been removed, it needs to be replaced with a resistor. Otherwise the "video doorbell" will short out the transformer when it attempts to ring the missing bell. (If old bell wires shorted together instead of a resistor there)

[MrMobodies]

I see so this is to do with the bell. I am not sure what's he's got. I think it was a wireless thing he he told me linked to the base but I'll look tomorrow.

Thank you very much for your comments and very helpful.

[shabaz]

If the video doorbell is designed to replace the button and ring the original bell, it needs the resistance of the old bell in the circuit. So if the old bell as been removed, it needs to be replaced with a resistor. Otherwise the "video doorbell" will short out the transformer when it attempts to ring the missing bell. (If old bell wires shorted together instead of a resistor there)

Exactly that (with the slight caveat that I believe/speculate the newer doorbells current-limit so that there won't be a complete short, and they have in any case confused no end of users because they don't explain it, they just say 'no resistor required', but of course many users will instinctively not want to do that when there's conflicting information, old YouTube videos, etc).

I think it's safer all round to just stick in the resistor if there's ambiguity in the instructions of whatever doorbell is being installed, or simply buy a mechanical chime and stick that in series (it doesn't usually hurt to have the extra sound! : )

The first week or so, the battery level needs to be monitored (at least I had to do that with Ring) since it charges slowly, and when it's close to 100%, then it tends to remain approximately there (mine is currently at 95%) and will vary slightly depending on how often it is consuming more power (e.g. if it's facing a busy road maybe), but overall, I've never had the battery deplete (it is not facing a road). It's probably not good for the battery to be charged so fully always, but as mentioned it's lasted 3 years so far, so that's not too bad.

[EPAIII]

Best argument against getting a Ring or Eufi video doorbell I have seen. Thanks for the heads-up.

[Zucca]

worth to mention that in my ring installation I was required to put a "white box" in parallel to the bell.
I assumed it is for trickling energy (lowering the bell impedance) to the ring so that the ring battery can be charged.

[exe]

I can only think of power dissipation. For 24V transformer, 2k resistor will dissipate ~0.3W in the worst case. That's not insignificant. On the other hand, most wire-wound resistors have power rating at least 1W even without heatsink. So, that might be the reason.

Of course, it's better to ask vendor, but playing a guess game is much more interesting)

[Xena E]

When I saw the title I thought it was similar to mine where a high power ww resistor is used to stop condensation within the camera housing...

Quite clearly not! 

[shabaz]

worth to mention that in my ring installation I was required to put a "white box" in parallel to the bell.
I assumed it is for trickling energy (lowering the bell impedance) to the ring so that the ring battery can be charged.

I can imagine that indeed being the case if the specific bell is either electronic, or has high resistance. The simpler bells (the ones that only have a solenoid pretty much! such as that Honeywell model suggestion) are candidates for not requiring any additional resistor.

The current required to flow through the Ring device is low since it charges at such a slow rate, but it will then try to look like a low resistance for a short period when the user presses the button.