Transformerless Power Supply - AC-110v to DC 5v 1A (60hz)

[JuanDH]

Hello Guys,

I have the following need and never been involved in designing one of these before so I need all the help I can get.
I need to be able to put a very small transformerless power supply (because of space) to feed my circuits, I have no
idea how those USB chargers out there are so small, maybe they are transformerless too? But don't know how do they
handle having the circuit live. I'm VERY concerned about having this on my circuits but have no idea how to make a
very tiny power supply to fit it into my project (I have very limited space).

I need somebody who could design this for me or provide me with all the possible help, not for free, of course.

Thanks!
Juan

[Ioannis]

Have a look at this:

http://www.picbasic.co.uk/forum/showthread.php?t=12249&p=81417#post81417

Ioannis

[JuanDH]

Hi Ioannis,

Thanks for the link. I've also searched the entire forum looking at the different posts (invested quite some time there) but the power supply you mention is for 220v not for 110v and as I don't have any experience on the matter I prefer not to "guesstimate" on this kind of designs. I saw a thread where the user Melanie posted, what it looks to me, at least a safe power supply (as much as this ones can be): http://www.picbasic.co.uk/forum/showthread.php?t=3265&page=2

Thanks
Juan

[JuanDH]

I don't think it is isolated and it is expensive, but is everything in one module, it is attractive at least. Experiences?

http://parts.digikey.com/1/parts/1884291-conv-ac-dc-90-264vac-5v-1a-rac05-05sb.html

Thanks!

[dhouston]

... the power supply you mention is for 220v not for 110vDid you read the entire thread?

Also, you asked for transformerless and now want isolation. You cannot have both.

[JuanDH]

I did, I'll give it a try and see how it works with 110v

Regarding the isolation I thought that this module could be something "magical" :)

Thanks

[dhouston]

Regarding the isolation I thought that this module could be something "magical" :)
If you are referring to the module at Digikey, it's a 'switching' power supply. They are isolated and they have a transformer - there's no magic. Why can't you use an external 5V/1A (or more) SMPS, readily available for $5 or less? I almost always design for them.

[JuanDH]

I would love to use one but I have 2 problems:

1) This circuit is going to be inside a closed plastic box with minor ventilation 4"x3"x2" deep.
2) Price, I can't find a good price for those power supplies.

I'm obviously looking at the wrong direction because you mention that there
are SMPS readily available for $5, will you please point me were should I start
looking?

Thank you very much.
Juan

[dhouston]

1) This circuit is going to be inside a closed plastic box with minor ventilation 4"x3"x2" deep.
All the more reason to use an external supply.
2) Price, I can't find a good price for those power supplies.http://arduino-direct.com/sunshop/index.php?l=product_detail&p=123
(http://arduino-direct.com/sunshop/index.php?l=product_detail&p=123)
(http://arduino-direct.com/sunshop/index.php?l=product_detail&p=123)

[JuanDH]

Believe me, my life will be MUCH easier if I can put an external supply is not that I don't want to do it.

Maybe buying those $2.5 opening them and using the boards inside them to my purpose.....

[dhouston]

If it must be internal, start here (http://www.maxim-ic.com/app-notes/index.mvp/id/4087)...

Other chip companies make similar ICs.

[Ioannis]

The Elektor circuit is working from 0 to about 39 volts. So it is not a problem for the 110 VAC.

You do not have to make any changes.

Maybe only R5 to a lower value, say 15 ohms, but I doubt it is going to be needed.

The design is very clever and very efficient.

Although no isolation is offered. Watch out!

Ioannis

[Docedison]

Well one very dangerous thought would to cut the ac terminals very short AFTER soldering wires to them for the AC supply and connecting the DC out to your project. I've done it but I ALWAYS made a plexiglass case for the supply (Looked Real Good albeit a poor means of construction) workable though if PROPER SAFETY considerations were foremost in mind.
The 'Better thing" might be for you to search Ebay for the correct item or a combo that will work, a wall wart and an internal switcher either buck or boost as conditions require could be purchased inexpensively. I know because I Frequently shop there.
Personally I would recommend a 'Wall Wart" for 2 reasons, First You don't have to build and test it carefully before you use it... (Power Supplies tend to be Real Important). and Second, they are very easily replaceable. All it takes is a matching Jack for the PS chosen.
Doc

[Docedison]

ANY Construction that Directly uses the PS Mains should be a last option and then ONLY by a competent Tech or better an Experienced Engineer... IMHO
You Could get your self DEAD or worse, Someone else...
Besides it is much easier to buy and install a connector for the right supply... IMHO
Doc

[JuanDH]

All comments and experiences are more than welcome. I just ordered the module from Digikey (Recom AC/DC) so at least I don't have to worry too much about it. It is costly ($14 for 5v 400ma) but I don't want to play with safety here and these little modules are UL certified.

Thanks