Plug-In Transformer to Power Doorbell over Cat5

I am trying to power my Wyze Video Doorbell using existing Cat5e cabling that runs from my rack to the doorbell. The run is about 75-125 feet. I have searched the forums on this topic but couldn’t find an answer for this specific configuration. I found this plug-in 24V/1A PoE 802.3af transformer on Amazon:

Here is what I am thinking:

  1. Plug this transformer into a wall outlet in my rack closet
  2. Plug the doorbell Cat5 cable to the output port (I don’t need to run any data through this cable)
  3. At the Wyze end of the Cat5 cable, strip the plug and twist pins 4/5 for positive and 7/8 for negative (that is brown+white/brown and blue+white/blue, per the 802.3af mode b spec)
  4. Wire positive and negative to the Wyze Video Doorbell

That seems to me like it should work, but I am no electrician.

Thanks for your input!

I’m no electrician either, but it sounds like that should work, the only thing I’m not sure about is the voltage, the doorbell specs are 16V-24V AC, ≥10VA, and this power supply is 24v 1a.

Electrician here. That power supply puts out 24va.

Thanks for the feedback guys. I realize that the transformer puts out 24va, but what I don’t know is if that is too much. Wyze advises that the doorbell requires a “minimum voltage of 16V and power output of 10VA”, but it doesn’t say anything about the MAXIMUM. If this transformer won’t work, what is the acceptable range of volts and amps for a transformer in this context? Also, my googling says that VA = V*A, but if that is wrong please advise (duh, I know, but never hurts to ask!).

Too much VA isn’t an issue, the doorbell will only take what it needs. You might have more of an issue with voltage drop, but the doorbell has a pretty wide range of acceptable voltages, so it should work.

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Thanks @speadie. So it sounds like you are giving a qualified thumbs-up to that transformer, subject to voltage drop concerns?

I thought about voltage drop and am hoping that the transformer has enough headroom over the doorbell’s minimum spec to get the job done. My math is that I could lose 33% of the voltage and 37.5% of the amperage and still have 16V/10VA reach the doorbell. According to this calculator, I will experience a loss of 1.1 volts over 150 ft using 2 pairs of 24 gauge cable, so I would need a transformer that outputs at least 17.1V. This calculator indicates that this transformer will deliver 20V after 150 feet, which is a 16% drop. Either way, I will be delivering more power than the doorbell requires.

VA is more of an AC power thing. It’s kinda/sorta like watts but it also takes into account power factor (leading/lagging phase angles).

The main consideration, as mentioned, would be voltage drop, not current draw, in this application.

I’m not sure what my doorbell cam is actually drawing but my old v2 would deplete a 20,000 mah battery in about 30 hours so you should be fine.

Yes. You could use a 100VA transformer to power the doorbell and it wouldn’t hurt anything - unless you shorted out the terminals, then with wires might melt.

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Um, PoE may be nice to have around for other purposes, but why not just use a regular doorbell transformer with this cabling? That is the power supply the doorbell is expecting.

Two primary reasons to use PoE: I’m lazy, and I’m cheap.

The laziness comes in because I already have Cat5 cable installed in this location. With PoE I only need to strip & twist the doorbell end of the cable. With a doorbell adapter, I will need to strip & twist both ends.

As for cheapness, the PoE plug-in transformer is $8. A plug-in doorbell transformer is more like $15-20. If I get a non-pluggable doorbell transformer, then I also have to buy wire and a wall plug to connect it to the outlet (which, by the way, is also more work, see laziness point above).

I wonder how many decisions in my life can be explained by one or both of those factors…

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“Those are good reasons.”

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PoE adapters such as the one you bought in Amazon, outputs in DC not AC. Specs of Wyze doorbell requires AC voltage and will not work on DC voltage. How this helps.

Well, he or she could also convert it to 5V DC at the end and use the hidden USB input.

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I’ve tested my doorbell and it will run on 24 VAC or 24 VDC. Just stuck a bridge rectifier in between the wyze and my transformer, no smoothing cap. Polarity is unimportant - I tried both ways.

If you take a look at the internal photos for the wyze doorbell, you will see that the first thing the AC goes into is a bridge rectifier, so having one external to the device wont be an issue.
image

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Nice, thanks. I have to assume something is also kicking the resulting DC down to 5V?

Thanks for the feedback all. In summary, the last few posts state that: (1) the Wyze doorbell can use AC or DC power attached to the external terminals, (2) does not need an external bridge rectifier (whatever that is), and (3) can step-down the input voltage to the proper level.

So… it sounds to me like the bottom line is that the plug-in PoE transformer should work. Did I miss or misread anything?

It should work, provided the injector doesn’t try to negotiate power with the powered device. Passive generally means the power is always there, but it also says it is 802.3af Compliant , which would generally imply some sort of negotiation. The only way to find out for sure is to try it.

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That is some extreme laziness because cutting and striping a cat 5 to use it’s wires is like a minute worth of work, maybe 5 if you’re really slow and fumbly. I’m a big fan of not saving money by trying experiments with products you now have to fiddle with returning, possibly at your own expense, when they don’t work. VS just getting the right thing in the first place. Sorry if I sound like a jerk but I’ve been there at that point in my life where i’m always trying to save a buck or two at the cost of time and sometimes spending more than i would’ve spent to do it right from the start, and I’m slowly but surely getting past that point. Time is money, and you only have so much time. If you buy the poe injector and the DC output is not accepted by the wyze doorbell, then you’ve just negated all the cost savings and time savings, if you go the return route you know how that goes, could be a couple of hours of time wasted on with customer service and probably have to pay shipping to return it, and drive to ups store to send it off. If not you still have to purchase and install the ac transformer one way or another. If someone here could confirm they have used such a power supply and it worked just fine, that would be one thing, but as far as I can see, some people are saying it might work, not it will work.

I have tested the wyze doorbell and it works just fine on DC.