Everything You Need to Know About Wall Warts

If you work with electronics at any skill level you need juice. [Jon] has a great, and clearly worded tutorial about Wall Wart Power Supplies with pretty much everything you need to know about those little black boxes hanging off of your outlets.

The whole thing starts off with the basics like transformers, rectification smoothing and regulation, then moves on to the different basic types, dedicating a page to linear, regulated and switching types, giving output performance charts under different situations.

Also included is a run-down of DC barrel jack structure so you get the right plug every time, wall wart type identification, a random sample comparison test, and a good selection of formulas to even keep the old hats reading along. Although you might want to set aside a little time at 9 pages and some Q/A in the comments, it might take a moment to read.

Comments

  1. TMXOD says:

    500 Internal Server Error‽

  2. tamasko says:

    This sounds awesome but the site is down. Mirror?

  3. Thuli says:
  4. Elias says:

    Why on earth are they called wall warts?

    http://en.wikipedia.org/wiki/Wart

    I don’t see any warts on my walls for sure.

  5. Olivier says:

    @Elias : the wart is the power supply you plug in your wall.

  6. Eli-0 says:

    @Elias – Because they often look ugly when plugged in, compared to a standard electrical cord. Like a “Bump” on a smooth wall…. or a …wart on smooth skin.

  7. Slipster says:

    … Problem loading page. Looks like it’s overloaded.

  8. Elias says:

    Thanks for the explanations guys :)

  9. TecKnight says:

    I am getting:
    DB function failed with error number 2006
    MySQL server has gone away SQL=SELECT name, link,id FROM jos_picmicro_menu WHERE published=’1′ AND link LIKE ‘index.php?option=com_comprofiler%’
    when trying to access link.

  10. Jon says:

    The site’s server is 100% loaded at the moment. It’s being looked into.

    I don’t think it’s too much traffic from Hack-A-Day, but thanks if it is!

    Please check back later if you can’t get through now.

    Jon

  11. G8erB8 says:

    It loaded for me. Thank you so much for writing this. I’ve been putting off getting a power supply for my project just because I didn’t fully understand everything. This is a huge help.

  12. error404 says:

    Coral Cache!

    I’m curious about this but alas I’m getting a blank page.

  13. LordNothing says:

    this article just does not want to be read

  14. Jon says:

    I think the site is down for a bit for maintenance now. The article has received over 5000 hits since the Hack-A-Day post this morning…amazing!

  15. I’m the web admin @ digital-diy.com and I’m sorry about the load issues guys! The sheer volume of HaD traffic put the site to test..

    Have made some updates and it might be a little slow, although it’s working now.

  16. Jon says:

    Here is an alternate site if the above link does not work. The plot links are being added.

    http://www.clever4hire.com/special-articles/home/ac-dc-power-supplies—using-wall-warts

    Sorry for the problems at Digital-DIY.

  17. freddyb says:

    Pawn shops are a great source for wall warts. They usually have a large cardboard box full of them by their electronics area. They’re usually $0.50 to $1 each.

  18. setlahs says:

    I’d be interested in information on hacking switching power supplies to output different voltages.

  19. mikellekim says:

    If you feel like expanding the article, it would be interesting to have efficiency comparisons among the different units.

  20. Jon says:

    “If you feel like expanding the article, it would be interesting to have efficiency comparisons among the different units.”

    Interesting you should say that. This was part of my original plan! I was using a Kill-A-Watt to measure AC watts, VARs and power factor but the Kill-A-Watt just didn’t have the required resolution for the measurements.

    Some tentative results are that a switcher is hands-down the winner at lower output levels. But if a switcher and a linear supply are compared at near their rated load, the situation may be different. The switcher may draw less “real power” but when the power factor is considered, the apparent power is higher. You don’t pay the utility for apparent power, but if you’re using a generator or UPS, you have to generate the higher level.

    I’d love to do this study when I come up with a more accurate way to measure true power and power factor.

  21. mikellekim says:

    I have the same issue with my Kill-A-Watt. The error is especially obvious at low wattages (LED xmas lights for example).

  22. nixar says:

    I’m sorry but the linked article kinda blows. Repeating 5 times that you need a regulator if you use a linear power supply is also pointless. It’s missing the main point about linear supplies, the fact that they’re as obsolete as the aged casings they reside in shown in the pictures.

    They simply should not be used. Replacing them with cheap modern switched supply will pay for itself rather rapidly in electricity savings.

  23. Jon says:

    Actually nixar, several of the linear power supplies are from current-release NetGear products.

    I wasn’t able to complete “phase 2″ showing efficiency because of lack of resolution in the Kill-A-Watt but I do have enough data to suggest that switchers and linears when operated around mid-point in their range may be about a wash in terms of power used. Switchers win when plugged in and no load is connected but when under load, this may not be the case.

  24. nixar says:

    Switched power supplies used to be much more expensive — 20 years ago — because they required more advanced power electronics. Nowadays those components cost pennies, while the relatively high Cu content of linear supplies is not getting cheaper.

    That’s about the only advantage linear supplies had. They have much a worse PF, or at least switched supplies can easily be made to have much better PF.

    Switches supplies have, as you said, much better low load efficiency — in fact, they can be made to have as little consumption with no load as you’d want, while linear supplies are in the best case one big resistor.

    The thing is, there is no circumstance where a linear supply has better efficiency. They’re at most as good as bad switched supplies in some loads, and definitely worse the rest of the time.

    I have no idea why Netgear would ship those. Maybe on the low end they are more reliable?

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