Too far to work?

#21

Thanks for the update! I’ve read somewhere that USB power has a voltage drop after a certain length/run. Some of the longer cables on Amazon state they’ll be fine, but I do often wonder if that’s the case.

I have a Foscam that I’d like to replace with a WyzeCam. But the power cable length is something I’m mindful of given the distance. The Foscam uses a higher voltage power cable than the Wyze.

#22

https://www.calculator.net/voltage-drop-calculator.html

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#23

Thanks for the link!

Anyone have the specs on the cable and the power block?

#24

That’s a great link and has some very interesting information. However, using a standard plug voltage of 120V and the default wire size of 1 AWG (approx. 1/4") at 50ft (far longer than I need), I am given a voltage drop of 0.01%. Even if I go with a very small wire gauge of 10 AWG (approx. 1/10"), I get a voltage drop of 0.08%. A voltage drop of this magnitude would seem to be inconsequential.

Again, I’m not an electrical engineer, so there are variables here that I don’t fully understand, but it would seem that a distance of 25 ft with a standard gauge copper wire should not be lacking enough power to operate normally.

I just wish that the specs for operable distances would have been more clear before I embarked on this ill-fated attempt to get camera coverage to the far corner of my yard. There is obviously a limit to powered cable distance in addition to the better understood wifi range limitation, and you certainly can’t daisy-chain indefinitely. Having some data on the actual limitations of these cameras ahead of time would have changed my approach significantly.

#25

It’s only about 30 feet, and they make 25 ft cables just for this use case. I think the issue stems from the multiple cables. When I tested it and connected the camera with the long extension cord connected to the single 25 ft cable, it connected fine. But I needed more than 25 ft so I had to use an additional Wyze usb cable from one of the mounting kits, and that seems to be the issue. The additional 6 ft can’t be that much of a voltage drop, yet it won’t connect with that configuration.

Yeah, unfortunately the only option is to power from my sunroom. Believe me, if I had another option I would be exploring it!

#26

A 1-AWG wire is over 1/4 inches thick. Normal home wiring (120V) is 14 AWG for 15 amp circuit or 12 AWG for a 20 amp circuit. (The bigger the number, the smaller the wire.)

14 AWG house wiring (120V) runs all over the place with little voltage loss. But that’s big wire at 120V. Voltage matters. The lower the voltage, the more the drop. The higher the amperage, the more the drop. And, of course, the smaller the wire, the more the drop.

The cameras operate at 5VDC (not 120VAC). A typical USB cable might have power conductors of 22 or 24 AWG. When you buy them, it’s sometimes impossible to find out the actual conductor size.

For the sake of argument, lets say you have 22 AWG conductors running 25ft at 5 VDC and .7 amp. That gives you a voltage drop of over 1/2 volt or over 11%. String another 25 ft after that and you double the drop, putting the end voltage under 4 volts. You can see why that would start causing problems.

BTW, the camera and USB cable connection in the middle of the 50 feet is mostly irrelevant since the the two cables ends are essentially directly connected.

I’d suggest you plug some numbers in the calculator and then change one parameter at a time to see what the effect is.

Another example: Your 25’ cable, perhaps 22AWG, 5VDC and 1.0 amp (2 cams at .5 amp each). That give you and end voltage of 4.19. Now start with that, add 6 ft, 24 AWG at 0.5 amp. The end voltage is now 4.04. That’s way below the nominal 5VDC and not at all surprising that it causes issue.

Bottom line, you are best off getting as close as possible with 120V power before switch to 5V with the adapter.

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#27

Excellent information, thank you Loki. I know just enough about voltage to build computers, but certainly not enough to do calculations of this nature when diagnosing voltage issues around the house. As I suspected, I didn’t fully understand all those variables in the calculator and was arriving at some very incorrect numbers.

This was very enlightening and makes a lot of sense. I am going to play around with the calculator a bit to learn more about how this works, but I am sure your final example is accurate. Adding additional distance via Wyze 6’ extension cables to an already voltage-reduced 25’ cable is likely bringing my end voltage below 4, and a 20% drop certainly seems like it would cause operational issues.

Looks like I’m going to have to try to get some kind of extension cable out there to get power closer to the camera. I have my cables for the cameras under the eaves along the edge of the roof, and I can probably just add an extension cord to the cable harness without much trouble.

Thanks for your help, I really appreciate it! I learned a lot about wifi coverage and home voltage. I’ll report back when I have a working solution in place!

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#28

Great info Loki! Is there any way to measure the actual power output at the end of the USB able with something like a multimeter?

#29

You can measure the voltage at the end with a multimeter, but you need to do it under load. That would entail having a USB cable that been spliced into to expose the leads to connect the meter to. You could purchase something like this, but off on of the male, strip the wires and connect the meter there.

1 Like
#30

Great tip! Thanks!