Mains power supply for IOT devices

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I have some Sonoff SNZB-06P Human Presence Sensors I wish to install, I wish to 'spur' out from a mains wall socket, and provide power from a power supply module fixed inside a surface box.
This requires an Input Voltage of 5V 1A.

I note the input voltage for this is rated at 1A, this seems quite high for such a small device, is that because the Voltage is very low (5V).

I am considering something like this:

240v > 5v
Input voltage: AC 85 ~ 265v 50 / 60HZ or DC100v-370v
Output voltage: DC5V (± 0.2V)
Output Current: 350 mA
Power: 3.5W

Or

5V 2A
It but doesn't quote a Wattage.

I calculate the power consumption as W=amp x volts, but cant work this simple equation out.
How can a 5V 1A Output supply, equate to 350W ?? (5W=1A x 5V) ...confused.

I presume these little Power Supply modules are what you will get in say a plug in mobile phone charger, like this: (bigclive.dom is not a fan:
)

I also want to power a TRVZB Radiator TRV with a Power Supply, rather than run it off the batteries:
It takes 3x 1.5V AA batteries, so Power Input is 4.5V, but it has a motor in it, so will assume the power required will be more than the Human Presence Sensor mentioned above (the SNZB-06P)

Any thoughts appreciated
 
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While i havent taken a look at your links (I'm probably not in a position to advise if they are of good quality or not). Is there a reason you wouldnt want to either have a single gang socket with usb instead of a spur and those modules inside of it or even better, just replace the socket you was going to spur from and put a socket with USB on. Then you keep your sockets and gain the USB for the presense sensor. Or you can get euro modules with USB which might be better than a diy DC converter which might not be a good idea loose inside a backbox or have the right heat disapation etc.. not to mention if it goes wrong.

I have smart TRV's and I only replace batteries say once a year so rechargeable batteries would be easier although I get the idea of a permanent supply. I have used DC to battery converters for fairy/christmas lights before but I suspect you will have issues with the cable and battery cover unless you get the flat cable type ones or do a small cut in the cover. Do not do as the video has done and convert an actual battery and cut a usb just to save a few £, just get the premade ones from Amazon or wherever as I think they have a resistor in them to bring the voltage down to the correct one. This is the one I have personally used this christmas without issue (https://www.amazon.co.uk/gp/product/B0BJQC2H32?ie=UTF8&psc=1)
 
I note the input voltage for this is rated at 1A, this seems quite high for such a small device, is that because the Voltage is very low (5V).
I think it's ass-covering. It's unlikely it draws 1A continuously, but it is constantly broadcasting a radio signal so that's why it's not battery powered.
 
I wish to 'spur' out from a mains wall socket, and provide power from a power supply module fixed inside a surface box.

Alternatively, you could feed it from the lighting circuit - occupation detectors, usually work best, ceiling mounted. They are very unlikely to draw the 1amp.
 
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I have smart TRV's and I only replace batteries say once a year so rechargeable batteries would be easier although I get the idea of a permanent supply.

Such devices, tend to sleep most of the time, then just wake for the fraction of second, needed to do the sampling, and reporting to base.
 

Lots of ways to lose the batteries, but how well made are they from a Fire Safety point of view.

Is there a reason you wouldnt want to either have a single gang socket with usb
I dont want the USB cables unplugged by the occupant, otherwise the device stops working, I can see them doing so to charge what ever they bring into the property, I'm after it being permanently on, rather like a bathrrom fan.

The wattage draw will be very very small, so would assume very little heat generated.

Need to consider fire safety, this stuff is going to be in sleeping rooms, and powered up permanently.
UK mains and USB sockets from what I can see will be to a good standard, unlike all the chinese rubbish we see which the power supply modules I illustrate above will be, for some reason I am finding it a task to locate a good quality branded power supply module, they are mostly 'power bricks' or plug in PSs, again I do not want the occupant to be given the chance to unplug it.

just replace the socket you was going to spur from and put a socket with USB on
Why didn't I think of that !
 
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