Converting 240VAC to 12v DC

[2Pringles]

What components are needed to convert 240VAC to 12VDC?

 

[UNG]

A transformer and a bridge rectifier is a good start

 

[James]

https://www.amazon.co.uk/SHNITPWR-Switching-Converter-Transformer-Security/dp/B07TZMJBZX/ref=sxin_14_pa_sp_search_thematic_sspa?crid=L19W08Y1VIF4&cv_ct_cx=12v+dc+power+supply&keywords=12v+dc+power+supply&pd_rd_i=B07TZMJBZX&pd_rd_r=5afdf611-9a09-4c2b-a63e-52ba806b6bd1&pd_rd_w=uu3pS&pd_rd_wg=wC3ok&pf_rd_p=7468d229-fb8e-4951-8ff4-df03d0bdb454&pf_rd_r=541NKST46MAFS2B8MSY7&qid=1649522637&sprefix=12v+dc%2Caps%2C72&sr=1-2-b75715df-0cbd-4312-a971-de5362256967-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExTVJaMkRBMkpDS1hEJmVuY3J5cHRlZElkPUEwODE3NDgzM0FUNTU2S0tQTVRMSyZlbmNyeXB0ZWRBZElkPUEwODIzMjc0WThSNk9TVkIyNlRGJndpZGdldE5hbWU9c3Bfc2VhcmNoX3RoZW1hdGljJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

 

[2Pringles]

what about somthing like this guys?

 

[Lucien Nunes]

What current do you need at 12V and what type of device is it powering? There are many different ways of doing this, some are more suited to certain applications than others. For example, that LED driver might not work well for a 1A motor load because of the starting current. But a simple transformer-rectifier which would be fine for a motor, would be unsuitable for a piece of audio equipment due to voltage ripple.

So more info needed please...

 

[2Pringles]

What current do you need at 12V and what type of device is it powering? There are many different ways of doing this, some are more suited to certain applications than others. For example, that LED driver might not work well for a 1A motor load because of the starting current. But a simple transformer-rectifier which would be fine for a motor, would be unsuitable for a piece of audio equipment due to voltage ripple.

So more info needed please...

Hello Lucien.

They are mobile Routers, one 4G, one older 3g.

I am looking for the most compact smallest solution.

Also, the currents required for each device are

1x 12vdc 2.5amp
1x 5vdc 1amp

 

[Lucien Nunes]

Small switched-mode PSUs are what you want then. Regulated output is important but surge capability is not needed. There are literally hundreds of options, plug-in style, brick style, grounded, floating, low leakage etc. If size is super-critical you will have to trawl all the offerings trying to find dimensions. With a supplier such as CPC or RS there will probably be dims included in the product details, but the prices might be higher.

How about:

https://cpc.farnell.com/pro-elec/pell0021/5v-1a-uk-plug-2-5mm/dp/PW04596

as an example of a plug-in unit and

https://cpc.farnell.com/powerpax/sw3473g/ac-adaptor-12v-2-5a-c8-30w-vi/dp/PW04072

as an example of a mini brick.

You will need to choose a supply with the right DC connector (2.1 & 2.5mm are popular) and double-check the polarity. Almost all are positive inner but a small percentage are positive outer. Or buy a supply that meets your size constraints and fit your own connector.

 

[2Pringles]

Thanks for the help Lucian.

How about inline converters like these

www.mr-resistor.co.uk/item.aspx?i=7579

 

[2Pringles]

How about LED inline drivers Lucian?

providing the output voltage is correct, would they be appropriate?

 

[mainline]

How about LED inline drivers Lucian?

providing the output voltage is correct, would they be appropriate?

You need a well regulated, smooth DC supply so no not one of those.

It also doesn't instil confidence when they state : The AC-DC Convertor changes resistance from AC to DC

 

[brianmoooore]

Thanks for the help Lucian.

How about inline converters like these

www.mr-resistor.co.uk/item.aspx?i=7579

Definitely not! That's just an over priced diode in a case, or maybe four diodes if you're lucky.

 

[Lucien Nunes]

Those appear to be just rectifiers, that turn 12V AC into 12V DC, based on the statement: "This allows LEDs to be run off AC transformers." Why they would sell an electronic product with no specification (what current, voltage etc can it handle?) and no real description I am not sure. Anyway, no.

Ignore these lighting products, buy normal wall wart PSUs like the ones in my links. They are the types of product supplied new with the routers. Anything much smaller/cheaper/weirder probably isn't suitable.

 

[Avo Mk8]

How about inline converters like these
www.mr-resistor.co.uk/item.aspx?i=7579

If you look at the little diagram top right in your link you'll see that a transformer is required in the circuit, and then this appears to be the rectifier part. Using this on its own, powered from the mains, will destroy your routers!

Buy regulated psu's intended for the purpose, as per Lucien's post

 

[westward10]

Those appear to be just rectifiers, that turn 12V AC into 12V DC, based on the statement: "This allows LEDs to be run off AC transformers." Why they would sell an electronic product with no specification (what current, voltage etc can it handle?) and no real description I am not sure. Anyway, no.

Ignore these lighting products, buy normal wall wart PSUs like the ones in my links. They are the types of product supplied new with the routers. Anything much smaller/cheaper/weirder probably isn't suitable.

I believe he is trying to avoid these.

How to wire AC cable direct to DC cable > on Free Electrical Advice - Electricians Forums

Find How to wire AC cable direct to DC cable Advice and Help. How-to How to wire AC cable direct to DC cable in the UK Electrical Forum advice boards on Electricians Forums. How to wire AC cable direct to DC cable on ElectriciansForums.net Electrical Advice Forum.

www.electriciansforums.net

 

[brianmoooore]

There are inline PSUs available, which have a mains cable in and the DC cable out. Removes the large lumps from the wall socket, but they're still large lumps that have to go somewhere.
How about a 2 gang 13A extension lead, with the wall warts plugged into it, an tucked away somewhere? Not too tucked away, since they need ventilation to stop them overheating.

 

[mainline]

A transformer and a bridge rectifier is a good start

Followed by a capacitor and a regulator

 

[telectrix]

find a couple of peeps who are scrapping fauly routers or upgrading. beg the PSUs from them. I havwe a couple of netgear ones sitting around and occasionally used for experimental (flash,bang) projects by yours truly.

 

[Avo Mk8]

It used to be the case, maybe still is, that the approval process /CE marking /CB marking to get your new product legitimately onto the market (normally using an accredited test house), was much easier and cheaper, if the product was designed as low voltage, with all the mains filtering, associated EMC issues, and creepage and clearance hassle kept out of it, and 'subcontracted' by buying in a wall wart.
I think that's why there has developed such a proliferation of products using these annoying bulky plug-top(ugh) power supplies, where the lump hangs down (or pokes up) exactly where you don't want it, and the wire always comes out of the wrong end

 

[Lucien Nunes]

Yes that is true and it's a convenient method that I rely on when making one-off speciality devices. I have to say that I am generally a fan of external power supply units. There can be advantages in keeping the PSU heat, volume, weight and electrical noise out of the product itself. Also in the (surprisingly rare) event of failure, wall warts can be easily and cheaply replaced without having to send the gadget away for repair. There was almost a whole industry dedicated to reparing the small SMPSUs in early digiboxes that were notoriously unreliable, which would have been avoided had the PSUs been external. Yes they can cause socket clutter but how serious is that really? I can live with a bunch of wall warts under the 'gadget table' in the lounge but if the gadgets had integral power supplies they would be larger and wouldn't all fit on the table.

I have a specific reason to favour external PSUs in my particular line of electronic work, because they allow me to modify and improve power configurations when integrating hardware into a system, without hacking and invalidating warranties on the products themselves. For example, my portable media capture & processing systems are designed to operate from external Li-Ion battery packs or mains. I build a custom multi-input, multi output power supply chassis that powers a dozen or more separate products at 5, 12 and 48V and gives UPS functionality if a battery is left connected while on mains. It combines low noise, very high reliability (sometimes dual redundancy) monitoring and control in a convenient, all-ELV chassis. The mains input goes via two or three 19V 240W medical grade level VI power bricks that can be hot-swapped, so I keep the mains out of my own power chassis too. If the powered devices were mains-fed, an inverter would be needed which is less efficient, typically less reliable, acoustically noisier, tends to produce horrendous electrical noise (HF inverter) and/or adds serious weight and bulk (LF inverter.) Otherwise I would need to open and void the warranty on dozens of pieces of gear costing up to £5,000 each to bypass the internal PSUs.