How to power multiple sensors?

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Talkiet

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Topic # 222612 20-Aug-2017 19:25

I'm after options to power multiple sensors in my house. They are a combination of Aeotec Zwave sensors and NodeMCU based (8266) sensors. They can both be powered by USB power and there are battery options available for both. Battery life for the Zwave gear is good, but it's atrocious for the wifi based gear.

I can see my options as:

1) Batteries. This isn't really feasible given how hungry the ESP8266 devices are.

2) mains powered USB PSUs everywhere. Messy and would require extension cords etc...

3) Low voltage (12V) power bus through the roofspace with 12V to USB adaptors breaking off the bus for the Aeotec gear and powering the NodeMCUs directly.

4) [edit - just thought of this] Could I use powered USB hubs in a couple of places? Is USB power ok across a 5 metre run on a decent cable? How about on a rubbish cable?

Option 3 looks the most attractive to me but a couple of questions...

- Do I need an electrician to install a 12V power system? Can I do it myself without breaking any laws/code?

- I presume with reasonable sized wire and PSU there would be negligible voltage drop across a 20-30 metre run? (All the devices seem tolerant of 9 volts at worst on the low end)

- Assuming it is permissable, what would be a good PSU to use? I figure with up to 10 devices drawing maybe 100ma each, a good sized 3-4A PSU would be ample?

Any other suggestions?

Cheers - N

Talkiet

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Reply # 1849353 20-Aug-2017 19:34

Option 5) A bunch of POE -> USB adaptors... I have a few spare POE ports I could use for this, but seems overkill

davidcole

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Reply # 1849357 20-Aug-2017 19:42

I would have thought a powered hub might do it.

Also how would you have seat with 12v Poe and stepping down to 5.5v for USB?

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Talkiet

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Reply # 1849360 20-Aug-2017 19:45

With something like this (Aliexpress link TinyURLed) for 12V

https://tinyurl.com/y9pqgdou

Or this for POE to USB

https://tinyurl.com/y6w6u4yx

Cheers - N

davidcole

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Reply # 1849365 20-Aug-2017 19:56

Right. What about a 5v 5a ac adaptor? If such a thing exists?

Talkiet

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Reply # 1849414 20-Aug-2017 20:20

davidcole: Right. What about a 5v 5a ac adaptor? If such a thing exists?

I'm not sure what you mean (in terms of where to use it)

It would be unsuitable as a power source for the whole low voltage run due to voltage drop, and not required for the ESP8266 devices (They will happily use whatever the 12V drops to over any reasonable run). The USB powered devices could have a simple 12Vdc to USB power converter. Not sure where I'd use a 5V AC adaptor.

Cheers - N

DarthKermit

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Reply # 1849421 20-Aug-2017 20:28

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I'd go for a decent 12v transformer with wiring to power the gadgets.

Are you able to add up the total milliamp load all the devices will consume?

Talkiet

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Reply # 1849424 20-Aug-2017 20:30

DarthKermit:

I'd go for a decent 12v transformer with wiring to power the gadgets.

Are you able to add up the total milliamp load all the devices will consume?

Yes, best estimate so far is sub 2 amps worst case, more likely to be sub 1amp total.

I'm leaning towards this option myself, just installing the wiring and then plugging an off the shelf PSU into an existing AC outlet and plugging the PSU into a fused socket for the 12v wiring.

Cheers -N

DarthKermit

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Reply # 1849427 20-Aug-2017 20:36

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I installed fixed 12 volt wiring in our house to power a few different systems. All the smoke alarms and around ten super bright LEDS for inspection lights. I got a grunty 3 amp PSU to power it all. No problems with voltage drop it would appear. It's good to have a decent power supply to allow for future additional demand on the system.

hio77

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Reply # 1849432 20-Aug-2017 20:41

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ESP8266 becomes it's own when you use sleep mode, otherwise yeah they will drain hard.

I run them on 18650s that i change out when the voltage drops a little low, normally get a few months on my setups.

if your going to run them from a signal source, that can work long as you have the amps, just be aware that fluctuations in power and ESP8266's are not friends, they like a nice clean power source...

normally i couple a cap or two with it, mainly to smooth out the bursts when traffic is passing.

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Aredwood

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Reply # 1849532 20-Aug-2017 23:55

I vote the 12V power distribution system. Mainly as far easier to add battery backup at a later date if you want. 5V buck converters are cheap as chips on Aliexpress - Switchmode powersupplies that step 12V or so down to 5V.

Although since the devices are such low current draw each - you might as well just use 7805 voltage regulators. As they are super simple to wire up, and being a linear type voltage regulator - they output very clean power. The 7805 just needs a small capacitor between input and ground, and another between output and ground. See datasheet for values.