justinm001
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Alernative ways to power a Pi

Sat Apr 22, 2017 4:06 pm

How can I power a Pi 24x7 without using an outlet? Would any of the ways below work or are there other ways i'm not thinking of?

Plugged into a POTS phone line (I believe 48VDC 100ma)
Somehow pull power from next to a breaker box (without splicing wires)
Use solar power and battery box

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davidcoton
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Re: Alernative ways to power a Pi

Sat Apr 22, 2017 4:38 pm

1) No
2) No
3) Yes, but you will be surprised how big the panels and battery have to be -- especially if you don't have tropical sunshine.
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Re: Alernative ways to power a Pi

Sat Apr 22, 2017 6:06 pm

a POTS line won't provide 48V while you draw 100mA from it.
addiitionaly the telephone operator will probably disconnect the line when you draw power from it for too long.

W. H. Heydt
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Re: Alernative ways to power a Pi

Sat Apr 22, 2017 6:17 pm

To expand a bit on Mr. Cotton's response...

1. 48V + Pi = fired Pi. Voltage input is specified as "5v +/- 5%", so 4.75v to 5.25v. The power protection circuitry can handle up to 6v to 7v, but after that, it will fail and the board will be destroyed. In theory, you could take the 48v and do DC-DC conversion down to 5v, but even at 100% conversion efficiency, 48v at 100mA is only 4.8W. For a Pi2B, you need 5v at 2A (more for a Pi3B, less for other models), or 10W. And besides, if you try it, your local phone company will Not Be Amused, and they will have their regulators on their side.

2. Again, in theory, you could use an induction tap, reduce the voltage and rectify the results. How much of an electrical engineer are you and how well do you know your local building codes as they apply to electrical power? (i.e Can you do it both safely and legally?)

3. As noted, people have done this. Start with your full power requirements. Initially, you can assume 5v at 2A, or 10W. So 240Wh per day. On average, you get daylight about 50% of the time, so at a minimum you need twice enough solar voltaic power than the running power of the Pi, or 20W. However, sun angle will reduce how much you get. Climate will reduce how much you get (cloudy or rainy weather), local conditions (shade or partial shade at times during the day), and seasonal variation (minimal daylight in the winter). So you should probably plan for at least twice as much, or 40W capacity. Charging a battery isn't 100% efficient, nor is discharging one, so you will want even more more solar capacity, probably in the 60W to 100W range. Your battery needs to have the capacity to run the Pi for two or three days, at least, to allow for inclement weather. So the battery needs to be able to deliver on the order of 500Wh to 750Wh, or--in round numbers--1KWh.

This is all "back of the envelope" or "off the top of the head" stuff. To do it right you need to sit down, research the gear you're going to use, check spec sheets, and generally do a detail design with *all* the relevant math. It'll probably take a couple of iterations through the design before you have something that will actually do the job.

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Re: Alernative ways to power a Pi

Sat Apr 22, 2017 6:30 pm

Get yourself a 20 watt PV panel a 7 amp hour battery and an inexpensive charge controller. You can optimize the rpi usage by lowering cpu frequency and other strategies like turning on and off when needed.

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Re: Alernative ways to power a Pi

Sat Apr 22, 2017 8:17 pm

justinm001 wrote:How can I power a Pi 24x7 without using an outlet?
Do you need a pi to do what you want? They are not intended for this sort of thing and therefore require extreme measures compared to something like a microcontroller. Are you collecting data?

justinm001
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Re: Alernative ways to power a Pi

Sat Apr 22, 2017 8:38 pm

We have a lot of equipment in networking closets and many are without power in room. We're looking for a way to power a Pi without having electrician wire us an outlet. a couple have a standard screw in light bulb so we could use one of those adapters to get outlets but others either have florescent lighting hard wired in ceiling or no light. There's always power lines in the room and breakers

Se we know we could use POE but that isn't readily available at all locations.
For analog phone lines coming from a phone system (right off 66 block) they should provide a solid 48v and we could use a couple lines together. We're thinking spare extensions not even plugged into the system.

Cost isn't really a factor here, since it would cost a ton to have electricians run power just for this.

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Re: Alernative ways to power a Pi

Sat Apr 22, 2017 9:29 pm

PI consumption isn't 5V 2A thats max power. Pi 3 B with wifi is only 250mA (1.2W) zero is only 80mA (.4W) This should be plenty to pull from a phone line with a step down conversion to 5v, right? I understand it'll kill the line but if that line isn't used for anything anyways it shouldn't affect anything.

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davidcoton
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Re: Alernative ways to power a Pi

Sat Apr 22, 2017 10:22 pm

I think you will find that the most cost-effective solution in the long run is to get some mains sockets installed -- especially if there are already mains distribution boards and breakers. It should not be prohibitively expensive if you order sockets for several closets at the same time.

Second option would probably be POE, but I have no experience of the costings or practicalities.

Solar is a poor option indoors, the panels only work well in good sunlight.

(Disclosure of interest -- I earn my living as an electrician :))
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peterlite
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Re: Alernative ways to power a Pi

Sat Apr 22, 2017 11:47 pm

Example solar powered Pi Zero: viewtopic.php?f=41&t=176221
Some parts are cheaper in other countries. Some countries have less sun and need more expensive panels.

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Gavinmc42
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Re: Alernative ways to power a Pi

Sun Apr 23, 2017 2:33 am

I use DIY POE for my CamPi's.
Only 12V going up the Ethernet cable.
Simple 12V injector after the switch and a power/signal splitter at the Pi End.
The power splitter was diy from a RJ45 IDC socket and 12V cigarette USB power adapter

No reason it won't work in reverse?
Just need attention paid to the network cables/routers etc.
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Re: Alernative ways to power a Pi

Sun Apr 23, 2017 9:57 am

I'm struggling to understand your situation.

You're asking if solar power would be an option ... are these networking closets out in the wilds, somewhere?

You say "... many are without power in room" but then say "... There's always power lines in the room and breakers". Do I understand that there's power, but no free mains socket?
An extra socket shouldn't cost much, next time someone visits the closet to do some maintenance.

How are you going to communicate with the Pi?
If you are going to use some wired network, then Gavinmc42's solution may be your best option.
Or, if you can reach both ends of the pots lines and disconnect them from the phone system, you may have a solution for both power and communication right there.

justinm001
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Re: Alernative ways to power a Pi

Sun Apr 23, 2017 11:57 am

The main issue is most network closets do not have any power outlets at all in the room. They're utility closets and usually contain breakers or some form of electrical conduit. This would be great if we could induction tap into the lines, or something without requiring an electrician running a line off it. I was thinking kinda how those non-contact power meters are able to measure current just by being around them.

We use these closets to connect all data and phone lines in the building and they don't have any outlets in them, just patch panels (66 and 110 blocks). I can think of at least 10 locations like this, and it would cost over $1000 per location and take 6 months (slow approval process) if even approved. I figure for $1000 there's a cheaper way to power a Pi.

They already make POE hats for Pi and we could use standard POE injectors from the switch but that wouldn't be ideal if there's any other way to power these.

Can't most solar panels work with florescent? If we get large enough solar cells and a battery, then leave the lights on 24x7 in the room, it should work fine, right?

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Re: Alernative ways to power a Pi

Sun Apr 23, 2017 12:10 pm

It'd be good to know where (country) OP is located - or, more precisely, where this project is taking place. My reading is that it is not in the 1st world, and that that affects the economics a lot. Most of the thread responders seem to be assuming that it is 1st world.

(Would love to be told otherwise, but that is my read at the moment)
If this post appears in the wrong forums category, my apologies.

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Re: Alernative ways to power a Pi

Sun Apr 23, 2017 3:31 pm

justinm001 wrote:work with florescent? If we get large enough solar cells and a battery, then leave the lights on 24x7 in the room, it should work fine, right?
That would probably--over time--cost more that having an outlet added to the closet. You'd be converting electricity to light, and then back to electricity. An inefficient process, at best.

justinm001
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Re: Alernative ways to power a Pi

Sun Apr 23, 2017 9:27 pm

We're in the US. The issue is we need to monitor events in those types of closets but don't want any permanent changes done if at all possible.

justinm001
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Re: Alernative ways to power a Pi

Sun Apr 23, 2017 9:33 pm

W. H. Heydt wrote:
justinm001 wrote:work with florescent? If we get large enough solar cells and a battery, then leave the lights on 24x7 in the room, it should work fine, right?
That would probably--over time--cost more that having an outlet added to the closet. You'd be converting electricity to light, and then back to electricity. An inefficient process, at best.
Usually they have 2x32W florescent bulbs in a fixture, We're talking small closet. We estimate the costs for an electrician to run a line is about $1000 (were severely overcharged for structure changes). If we leave the lights on 24x7x365 at a standard .10KWH that puts us at $56 a year. Would take 20 years before it becomes cost effective.

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Re: Alernative ways to power a Pi

Sun Apr 23, 2017 9:52 pm

justinm001 wrote:
W. H. Heydt wrote:
justinm001 wrote:work with florescent? If we get large enough solar cells and a battery, then leave the lights on 24x7 in the room, it should work fine, right?
That would probably--over time--cost more that having an outlet added to the closet. You'd be converting electricity to light, and then back to electricity. An inefficient process, at best.
Usually they have 2x32W florescent bulbs in a fixture, We're talking small closet. We estimate the costs for an electrician to run a line is about $1000 (were severely overcharged for structure changes). If we leave the lights on 24x7x365 at a standard .10KWH that puts us at $56 a year. Would take 20 years before it becomes cost effective.
Don't forget the cost of the photovolaics, their installation costs (do you need to have the wiring for them done professionally as well?) and the periodic replacement cost of florescent tubes.

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Re: Alernative ways to power a Pi

Mon Apr 24, 2017 6:44 pm

If there are light fixtures in those cabinets you have power available for minimal effort. T'ain't rocket surgery.
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davidcoton
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Re: Alernative ways to power a Pi

Mon Apr 24, 2017 8:25 pm

timrowledge wrote:If there are light fixtures in those cabinets you have power available for minimal effort. T'ain't rocket surgery.
Except that power (sockets) and lights are usually on different circuits, for reasons of circuit capacity, protection, and cable size.
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CarlRJ
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Re: Alernative ways to power a Pi

Mon Apr 24, 2017 9:03 pm

Random thought - how often do you have personnel visiting these closets for routine/scheduled maintenance? Would a car or truck battery (w/suitable voltage converter) run a Pi that long (with a suitable safety margin)? Take the solar cells and nine different ways of tapping into room power out of the equation and just use a d*mn big battery, swapped out for a fully charged one occasionally. A Zero doesn't use much power (assuming you want an ethernet jack for monitoring, you could use one of these or these). If you have enough of these to do perhaps you could find, or commission, a HAT to monitor the battery's level, so your software could send a warning a few days before running out (if you built a HAT, it could also include other sensing circuitry you may want - say room temperature). Offers the advantage that even power failures to the closet won't interrupt its monitoring. And there'd be no permanent changes to the closets. Just a thought.

Say, monitoring equipment in large numbers of network wiring closets without permanent modifications - you don't work for the NSA do you? ;)

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Re: Alernative ways to power a Pi

Mon Apr 24, 2017 9:49 pm

CarlRJ wrote:Random thought - how often do you have personnel visiting these closets for routine/scheduled maintenance? Would a car or truck battery (w/suitable voltage converter) run a Pi that long (with a suitable safety margin)?
Deep discharge marine battery would probably be best in this sort of setup. Something with, say, 60Ah rating at 12v, so 720Wh. A Pi0 need about 1mA at 5v, or 0.5W, so 1440 hrs., about 8.5 weeks or 2 months. If the closets are checked reasonably frequently, then the battery could be scaled down as appropriate.

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Re: Alernative ways to power a Pi

Mon Apr 24, 2017 11:45 pm

Been some solar panel discussion on posts.
Mainly because a year of batteries for 24/7 Pi turns out to be car sized.
As big as a car :o Not a car battery.

Basic you are looking at 100W for 24/7 but that is outside.
With lights on 24/7 maybe 20W, except the power you get from lights is 1000 times less.

I've done some tests with special low light panel 40mm sq, it will give 40uA inside, outside it is 40mA.
Maybe panels really close to light, thin film ones are best for the low light levels.

Swapping batteries weekly may be a way to do it.
Model Zero - 80ma 5V battery 1.92Amphr/day - 13.44Ahr/week, so a standard 12V 9Ahr gel cell should work.
Bigger Pi's = bigger battery
You can now get 12V/9Ahr LiFePO4 equivalents, much lighter and probably you will get more cycles from them.
Seen them for as low as $70, you can get them up to about 20Ahr, getting common for motor cycles etc.

If you can duty cycle then, much longer battery life,
Turn Pi on 1 minute every 5 minutes and you now have a monthly battery swap.
Turn it on for 10seconds every 10 minutes and the same 12V9Ahr battery is now a yearly swap.
10 second boot? Well that's one reason I use Ultibo, 2 sec boot ;)
Add solar to this and maybe no swapping.

As they are in Network closets then you have cables you can do POE with.
You just inject power at the other end, at the PC/terminal/wall socket end.
You just need a power splitter in the closet to get the power off the cable.
Just make sure the cleaners don't unplug your power injector so they can use their vacuums :oops:
Only need access to just one cable per closet to get POE into it.
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Re: Alernative ways to power a Pi

Tue Apr 25, 2017 12:35 am

Gavinmc42 wrote: You can now get 12V/9Ahr LiFePO4 equivalents, much lighter and probably you will get more cycles from them.
Seen them for as low as $70, you can get them up to about 20Ahr, getting common for motor cycles etc.
At that price, installing outlets would be the cheaper alternative...even at the price the OP cited.

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Re: Alernative ways to power a Pi

Tue Apr 25, 2017 1:33 am

At that price, installing outlets would be the cheaper alternative...even at the price the OP cited.
I want the name of your electrical contractor :lol:
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