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169 posts

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Topic # 228853 25-Jan-2018 16:01
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I've seen some references and some questions where this has been suggested, but not seen any photos or success stories.

 

Has anybody run a 12v PSU to power multiple devices - I'm thinking getting rid of wall transformers (particularly in comms cabinet) and powering IoT devices without adaptors. If so, what are suggested PSUs and methods?


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  Reply # 1946779 25-Jan-2018 16:35
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Very interested in this as well (but don't have anything to share sorry).

 

A mate is almost at pre-wire for his new house and asked me about wiring/lighting options. I am meeting his sparky next week to discuss. I like the idea of running low voltage wiring around the house to all lights and light switches. Then run them all back to a central location. The idea being you buy/build a relatively simple controller which takes the switches as inputs, and the lights as relay driven outputs. 

 

Something like this... https://www.superhouse.tv/25-arduino-home-automation-light-switch-controller/

 

Not sure of the realities of this type of wiring, but in theory it seems to make a lot of sense. Can run 12V LEDs without the need of any drivers, can easily swap in/out different dimmers, controllers, automations, plus you can quite easily hook up a 12V UPS to run all your lighting in the event of a power outage.


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  Reply # 1946798 25-Jan-2018 17:22
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Been thinking about a low voltage system for quite some time as my plan is to go totally off grid. My understanding is that one drawback is significant voltage drop, particularly over longer runs, with a 12 volt system. I was thinking one possible solution could be to run 48 volts or greater and use DC - DC converters at the access points. Not an electrician so this is just an amateurs theory. Be interested to hear from someone who knows.


 
 
 
 


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  Reply # 1946870 25-Jan-2018 21:10
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Even in a 48 volt system you'd need far larger cables to transport the same amount of power as with a 230 V system.

Plus, DC has an inherent problem of corrosion at contacts and switch points.

Have you investigated the relative prices of DC-DC converters vs the usual 230 VAC - 12 or 5 VDC converters?

I've been off grid for 12 years. I like being able to use the same mod cons as my on-grid mates.

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  Reply # 1946874 25-Jan-2018 21:19
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Losing isolation of AC power adapters will be the biggest problem IMO. With AC wall warts, they are all totally isolated other than the RF filtering capacitor. No chance of any ground loops at all.

 

If you want isolated DC-DC converters, suddenly the efficiancy isnt there, and you may as well have just got normal AC power supplies. Efficiency of those are typically very high because of legislation.

 

Only real reason I can see it being worth it is for backup power, and I have all the critical gear (wifi APs and cameras) running off power over ethernet, so all I would have to do is get a commercial grade switch with a 48v input connector and use that to get power to those things from battery. Or use a UPS on it.





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  Reply # 1946879 25-Jan-2018 21:36
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I believe http://www.dreamgreenhouse.com/ has a fair bit of stuff about it

 

I've certainly done it with a DIY 12V UPS using PicoUPS and a DC-DC programmable power supply. Individually fused each device


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  Reply # 1946886 25-Jan-2018 21:46
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I too would like to get rid of the wall warts - my plan is to eventually use PoE for those devices (A couple of my devices are already PoE ready, the others I'll look into getting a PD splitter)


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  Reply # 1946939 26-Jan-2018 01:14
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I have my whole comms cupboard running from a central power supply. But the main reason was so I could have my devices on a 12V UPS system. Have also added a 270W solar panel. So I have long term backup capability as well. Each device is individually fused. And are divided into 3 different banks.

Regulated 12V with over voltage protection.

Direct battery bank voltage, 11V to 15V possible range.

And non battery backed loads.

Future plan is to also power my solar hot water circulation pump from the same system. But the pump motor is a mains powered induction motor. Which hates running from modified sine wave inverters. So to avoid excessive power usage, I will need a system that can start and stop the inverter to match when the pump needs to run.

Easiest would be to find one of those inverters that can detect when a plugged in device is switched on. So the inverter will start and stop itself as required.





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  Reply # 1946960 26-Jan-2018 07:26
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I used to run a handful of fans in a cabinet and LED lighting on 12V.

I grabbed one of those "mousetrap" transformers from an old halogen light. The black wire wound ones are best.

Worked mint...





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  Reply # 1946964 26-Jan-2018 07:47
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Aredwood: I have my whole comms cupboard running from a central power supply. But the main reason was so I could have my devices on a 12V UPS system. Have also added a 270W solar panel. So I have long term backup capability as well. Each device is individually fused. And are divided into 3 different banks.

Regulated 12V with over voltage protection.

Direct battery bank voltage, 11V to 15V possible range.
Do you have a link to the kind of PSU you used?

 

I'm not looking to go that far (a few m) so don't think the cabling diameter / efficiencies will be too extreme.


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  Reply # 1947012 26-Jan-2018 09:35
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The power supply I'm using is this
Click to see full size

Main advantage of it being simple rugged construction, and fully adjustable output voltage.

You need to decide right from the start if you want battery backup or not. As that changes many factors with your system design. Including what power supply to buy. As you need min 13.5V to charge a 12V battery.

Use a computer power supply if having battery backup is not a consideration. But get one that has a single main 12V supply, and DC-DC converter stages for the 5V and 3.3V outputs. As this type is perfectly happy with max load on the 12V rail, and no load on the other outputs.

The cheaper units use a single transformer with different tap off points to get the different voltage outputs. This type become unstable if you don't keep each output within the same % of its max load.





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  Reply # 1947029 26-Jan-2018 10:33
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phrozenpenguin:

 

Has anybody run a 12v PSU to power multiple devices - I'm thinking getting rid of wall transformers (particularly in comms cabinet) and powering IoT devices without adaptors. If so, what are suggested PSUs and methods?

 

 

Yes, I currently have a small PC power supply connected to many of the RG6 coax cables that I installed throughout my house and office when we built it back in 2006. I have RG6 and CAT5e running to all rooms and areas from a central 'star' cupboard.

 

We ended up with dozens of wall warts powering a range of devices using 12V, 5V and 3.3V then remembered that perfectly good DC conducting cabling was already available at most places because of the RG6 installation. 

 

I have built many IOT devices for sensor monitoring and home automation (mostly ESP8266 based circuits) that run from either 5V or 3.3V and also have other 12V devices such as network switches, routers for access points, landline phone units etc.

 

It is easy enough to calculate the total load on the supply and in my case, the load is well within the specifications.

 

They have all been running from a single PC supply (attached to a UPS also) for many months with no issues.

 

 

 

 

 

 

 

 


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  Reply # 1947039 26-Jan-2018 10:52
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Some PC power supplies have a trimmer inside to turn the voltage up a little. Too far and the over voltage protection kicks in but you should be able to get a little more.

12v is a pretty silly voltage to distribute tho. You can go to 50 and still be extra low voltage so 48 is the way to go. Or 36 if you're wanting to charge batteries so 3 in series will have a 42ish volt requirement. Also many more DC to DC converters are ok up to that sort of range.




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  Reply # 1947042 26-Jan-2018 11:01
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That is very interesting, I have RG6 run throughout my place as well (not being used)...


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  Reply # 1947051 26-Jan-2018 11:12
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SumnerBoy:

 

That is very interesting, I have RG6 run throughout my place as well (not being used)...

 

 

Yep, same here. In 2006 I was undecided if I should install RG6 or not but went ahead anyway. It has become useful for DC power.

 

It's a bit clunky fitting connectors to it for plain voltage but a bit of good old stripping and braid twisting into plain screw connectors works fine.

 

I also made up some custom 'tidy' fittings using short pieces of RG6 to convert the wall plates screw fittings into more usable DC output socket connections.


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  Reply # 1947054 26-Jan-2018 11:14
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datahawk:

 

I also made up some custom 'tidy' fittings using short pieces of RG6 to convert the wall plates screw fittings into more usable DC output socket connections.

 

 

 

 

Got any pictures?!


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