wall chargers as a power source?

Discussion in 'General Electronics Chat' started by epic_newb, Apr 13, 2011.

  1. epic_newb

    Thread Starter Member

    Apr 10, 2011
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    Firstly, as my name would imply I have very little understanding of electronics but am trying to learn so please bear with me.

    I am working on a simple led project and decided I want to use a stable power source vs the battery I was initially planning to use.

    I recently went to goodwill on a hunt for a regulated wall wart. I found two wall chargers. One, which outputs 9v and the other which outputs 12v. Would these work well for my purposes? I mean i think they should but maybe I am not considering everything.

    The model numbers are ACTM-09 and JOD-35U-07
     
  2. BillO

    Well-Known Member

    Nov 24, 2008
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    Are they marked AC or DC output?

    If they were at the Goodwill, I am guessing they are not regulated. Probably just a transformer with a rectifier circuit and a capacitor at best. If this is the case, then the output will vary a lot with the load you put on them. They may start out 15%-20% higher than rated voltage then nominally supply the rated voltage at the rated current. If this kind of variance is tolerable for what you want to do they should do fine.

    If you need rock solid voltage with little or no ripple (TTL logic involved), you could build a small regulator circuit using an LM78XX regulator IC and a couple of capacitors.

    Another alternative is the switching regulator type of wall-wart that are readily available these days. They will maintain very close o their rated voltage from 0 amps to rated current. They can be had on eBay for chump change ($3-$5).
     
  3. epic_newb

    Thread Starter Member

    Apr 10, 2011
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    Yeah, they output DC, I figured they are probably not regulated which is kind of a bummer. I looked for wal-wart on ebay and cheapest one I found was about 10 bucks, at least for the 12v one I need for project. I have no idea how to make a regulator circuit unless you could point me towards the right direction? Otherwise, yeah I will probably just shell out the extra dollars for a regulated one.

    Also, I should just be able to cut the wires at the end of the adapter and use the positive and negative wires right?

    and interestingly enough one of the adapters i got is going for 20 bucks on ebay and the other one is going for 10. Not bad for 50 cents huh? :)
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    The ACTM-09 appears to be a regulated switching supply with an output rated for 12v @ 1.2A

    The JOD-35U-07 appears to be rated for 9VAC @ 300mA, 2.7VA. It's basically just a transformer.
     
  5. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
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    Unfortunately, wall warts vary all over the map and there's no way to tell by just looking at one. One day a few weeks ago I needed a wall wart for a project and measured six of them. I measured output voltage as a function of load current, typically going beyond the rated current by 10%-50%, depending on my judgment and what things looked like on the scope.

    I've attached two graphs of the measurements. The first graph shows regulation; the second shows RMS ripple as measured by a scope. RS was a Radio Shack wall wart and the Ktec and 4Hi were some unknown Chinese brand. The 4Hi was a no-name cheap looking one, but its performance was excellent. All the warts were around 12 V output, as that's what I needed for my project. I eventually picked one I had from an old external USB drive box, as it was the right size for my project.

    If you want a good one, I can recommend an HP one that was probably used for a laptop. It will have an IEC power connector on one end to take typical power cords. The one I measured was well-regulated and well-behaved.

    When my wife drags me to a thrift store, I always go look through their wall warts because they're usually between a quarter and a buck. You pays your money and you takes your chances.
     
  6. epic_newb

    Thread Starter Member

    Apr 10, 2011
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    wow lots of info thanks. im going to try my chances with the hopefully regulated 12v i got but thanks guys!
     
  7. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Unfortunately, the regional Goodwill manager in my area had the employees throw out all the wall warts (and remote controls) because she thought they looked unsightly. Can you imagine that...a Goodwill store that has junky stuff in it?
     
    Last edited: Apr 13, 2011
  8. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Yes, you can do that, but you might not want to if the connector is a one of the common coaxial types especially one with a 2.1 or 2.5mm center socket like some of these. http://www.minute-man.com/acatalog/Online_Catalog_Coaxial_Power_Plugs_199.html

    In addition, your 9v unregulated wall wart can have an external regulator added to it for not much money. You might be able to regulate it to 9v, could probably regulate it to 7.5v, and almost certainly to 6v or 5v. Or with a little more work, you could have an adjustable regulator. This would make a great project for a newbie. Wall warts are fun to work with and when you get them cheap, that's even better.

    Attached is a picture of a 12v wall wart that I added an external regulator to. I cut the cord off the wall wart leaving just enough to reach the input of the regulator inside the piggy back box and reattached the cord to the output of the regulator. The piggy back box is attached to the wall wart with hot glue.
     
    Last edited: Apr 13, 2011
  9. epic_newb

    Thread Starter Member

    Apr 10, 2011
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    Yeah, I was definitely thinking of making a power source that I could manipulate, I would need to learn how to make a regulator and then just add a pot right?

    I ended up cutting the cord but it worked out nicely i found which one was positive and negative by hooking it up to an led :p
     
  10. Jaguarjoe

    Active Member

    Apr 7, 2010
    770
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    Search around for an "LM317" adjustable voltage regulator. Depending on the input voltage it will adjust from 1.2 to 30+ volts. It only needs a few common parts to work.
     
  11. BillO

    Well-Known Member

    Nov 24, 2008
    985
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    Here are samples of some regulated power supplies I have used before off of eek-bay.

    These ones are fantastic for enclosed, permanent projects. They are a little more money. You can get them in all sorts of voltages and current ratings. http://cgi.ebay.ca/DC-12V-1A-Regula...161?pt=LH_DefaultDomain_0&hash=item5198773119


    These are more like old fashioned wall warts, but are very light and use switching regulators. Again, available in all sorts of voltages and usually about 1 amp. Great for all sorts of things.http://cgi.ebay.ca/DC-12V-1A-Power-...588?pt=LH_DefaultDomain_0&hash=item4aaa6e4a3c
     
  12. epic_newb

    Thread Starter Member

    Apr 10, 2011
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    0
    Wow nice, I'll definitely have to bookmark those. Thanks! :D
     
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