Connect with us

Convert from AAA to wall plug in

Discussion in 'General Electronics Discussion' started by sidefly, Feb 23, 2015.

Scroll to continue with content
  1. sidefly

    sidefly

    7
    1
    Feb 23, 2015
    Hello All! New member here looking for some assistance. I am just handy enough to get something really wrong, so I figured I would ask.

    I am trying to convert these candles from batteries to plug in. I don't want them all to fail if one goes out, so I need a solution for that too.

    http://www.walmart.com/ip/Mainstays-Flameless-LED-Pillar-Candle-Set-of-6/21151418

    I would prefer to set them up with banana plugs or something so they could be taken apart and put back together. I'm trying to safely power a cross at church vs constantly replacing batteries.

    I will be using a total of 12 candles.

    The big question: How? I'm really good at following directions!

    Thanks!
    Sidefly
     
    Last edited: Feb 23, 2015
  2. Arouse1973

    Arouse1973 Adam

    5,165
    1,087
    Dec 18, 2013
    Hello. Another member here, Bob gave an idea earlier in the week on something similar. He said use a wooden dowel the same size as the AAA battery and some electrical connections to each end. I am thinking maybe a couple of drawing pins pushed into the dowel.

    Then connect some wires to the pins and you can then connect them to a power supply.
    If you connect them in parallel, all positive terminals together and all negative terminals together then if one fails it will allow the others to still work. This is of course only if the LED candle doesn't fail short circuit.

    You may want to add a small inline fuse to protect the power supply. Make sure the power supply has an adequate power rating for all the LEDs connected together.

    Thanks
    Adam
     
  3. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    First, how many batteries in each? One AAA battery is 1.5V
    The candle I have uses 3, so I would need an AC-DC adaptor to provide 4.5V. You may need a different value.

    The next part is a little trickier... The current draw of each candle needs to be added together. We can loosely determine this if we know how many hours the batteries last in the candle. This will determine how many mAh you require for the AC-DC adaptor.

    Last thing... wiring. Please don't use banana plugs, the metal is exposed and you risk shorting out the replacement power supply. Instead, consider barrel plugs, or other plugs that encase the end of the wire in plastic in case it's dropped.


    When they are wired together, they will be wired in 'parallel' so if one light dies, the rest will remain lit.
     
  4. Arouse1973

    Arouse1973 Adam

    5,165
    1,087
    Dec 18, 2013
    I thought he meant banana plugs connected to the LED light? He needs to clarify. And yes I though one initially as he said convert AAA to wall wart. He needs to clarify this also.
    Adam
     
  5. sidefly

    sidefly

    7
    1
    Feb 23, 2015
    Thank you for the replies! The candles take 3 batteries each and seem to last about 8-12 hours (although the light noticeably fades some after about 6 hours). A barrel plug would do fine. I was thinking of putting a female and male one on each candle (a 12-18" wire with a male on it) - sort of a in/out for the power. Then they can be arranged in any order and easily disassembled. I would guess the AC/DC adapter would have a male on it to plug into the first candle in the series.

    I'm ok soldering the wires to the leads in each candle, I just want a permanent fix. I'm just not sure how to set it all up.
     
  6. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Well, The batteries are most likely arranged in alternating order side-by-side in the battery compartment.
    Lets use a worst-case draw of 8 hour life in a AAA. According to Wikipedia an alkaline AAA may hold up to 1,200 mAh (http://en.wikipedia.org/wiki/AAA_battery)
    For this to drain in 8 Hours would require the candle to draw 150mA.
    For 10 candles, this would require that you find an AC-DC adaptor rated for 4.5V and at least 1500mA (or 1.5A). You may, and are encouraged to buy something with a higher mAh rating depending if cost permits. The voltage rating MUST be 4.5V, although this situation may allow 5V to be used. (Test with a single candle if you are to try 5V)
    This satisfies the power requirement... now to actually wire it in.
    To attach the wire to the candle, you could simply use a piece of dowel to physically hold the wire in place against the metal pad the AAA battery normally contacts. Your candle may require 2 dowels, one to hold the positive wire, and one to hold the negative wire. From here, you can do whatever you want with the other end of the wire... May I ask however how the wiring is desired?
    Typically 'topology' would be to daisy chain them like Xmas lights, or to run a separate wire to each one from the power supply. The preference here would dictate what kind of connectors would be prefered.

    No worries, pictures and diagrams can be provided to help you out ;)
    If you can, post a pic of the batter compartment for us to see as well.
     
  7. sidefly

    sidefly

    7
    1
    Feb 23, 2015
    I can post a pic of the compartment later tonight. The batteries are definitly wired as if they were one long battery end-to-end. Here is my mock up of what I want:

    image.jpg
     
  8. Arouse1973

    Arouse1973 Adam

    5,165
    1,087
    Dec 18, 2013
    Have a look at Lithium Iron Disulphide also. Alkaline batteries capacity like most other batteries will change with load. I doubt you will get 1200 mAh out of a AAA driving these LEDs, but I might be wrong.
    Adam
     
    Gryd3 likes this.
  9. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    The 1200 mAh is unlikely, but I used it as a worst case reference. I would rather oversize than undersize the AC-DC adaptor. The actual batteries used could have had as little as 300-400 mAh :p In any case, Many cell phone chargers are now providing at least 2A outputs at 5V . I'd rather suggest a 4.5V, but I would use a 5V in a pinch.
    Good call that the actual rated capacity is usually never reached depending on current draw.. I keep forgetting that.
     
    Arouse1973 likes this.
  10. sidefly

    sidefly

    7
    1
    Feb 23, 2015
    Here is the front/back of the battery compartment: image.jpg image.jpg
     
    Gryd3 likes this.
  11. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Very very nice pics!
    Not only did you get the battery compartment, you took the bottom housing off so we now know how it's internally wired.
    The 150mA per candle that I estimated above is gross overkill, but following that number would leave you with a little head-room to add lights at a later date if you needed too. (perhaps as much as 50% more.. but I'm nervous exceeding that without any real measurements)

    So... next thing to tackle...
    Wiring!

    Do you want this modification to be permanent or temporary? I see you don't have a problem opening them up, are you willing or wanting to modify the housing for your project?
    There is also a budget to consider, both for your time and parts.

    Personally, I would put two barrel sockets in the bottom or side of the candle. I would then wire them in parallel and use small 'patch' cords to join them. This would look pretty clean and if a wire were to be damaged, anyone could simply grab a new patch cord and plug it in. This is also probably the more expensive route.

    Connecting a lead with a barrel plug on the end to each candle, and having a barrel socket on each candle would use far less parts, at the expense of having a wire permanently attached to a candle at a pre-set length.

    Lastly and less preferred... would be speaker box terminals or another type of bare wire termination. You could use speaker wire (as long as the gauge is large enough for 2A). To protect from hooking the wire up backwards, each candle should also have a diode wired internally. Each candle would only need one set of terminals... as two wires could be fitted together on each terminal. (The voltage drop on the diode would also make using the more common 5V AC-DC adaptors much more suitable. If you have trouble finding an AC-DC adaptor... simply look for a USB charger that can handle 2A and that will be plenty!)

    Edit: of course, you may use the now empty battery compartment for any additional parts you may want to add ;)
     
  12. sidefly

    sidefly

    7
    1
    Feb 23, 2015
    So it appears the center of the barrel connector is the positive (let me know if this is wrong). In summary I need a 4.5-5V 2A power supply.

    I like the idea of two females on each candle. So here would be my plan:
    1. solder the center pin of both females together with a wire then use a second wire to solder it to the candle positive connection.
    2. solder the outer connection of females together with a wire then use a second wire to solder it to the candle negative connection.
    3. use jumpers to interconnect the candles.
    4. plug the power supply in anywhere and they all should light.

    Good/bad plan?
     
  13. davenn

    davenn Moderator

    13,786
    1,937
    Sep 5, 2009
    look on the label of the plugpack to confirm that
    It is USUALLY the case but not always
     
  14. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Exactly what I was thinking!
    Of course, when you daisy chain them together, the very first and very last connected candles will have the 'open' socket to feed in power. If you are fine with this proceed! Otherwise, you could stick a third female socket in a 'hub' candle which would allow you to put power in anywhere in the middle of the string of candles. (Wherever the 'hub' is)

    Now... as far as the barrel plug is concerned, they are often center positive, but they can be wired with the center negative too!
    Take a look on the pack that plugs in the wall like Davenn suggested, you should find the following picture on it:
    zsp7C.png
    If this image does not exist, you will need to determine this yourself... Ideally, you would use a multi-meter or volt-meter to test. Black probe on the outside and red on the inside. If you get a positive reading, you have the left image, if you get no reading or a negative reading you got the right image. (Swap the red and black probes to be sure)

    As far as wiring is concerned, you can find all sorts of tables online telling you what gauge wire you need to handle the amount of current you will be providing to the lights.
    Personally, I use the table from : http://www.powerstream.com/Wire_Size.htm

    So... what does that mean exactly? Well... if the wire is too thin, or too long the voltage will drop in the wire! So the 4.5V AC-DC adaptor you have may only provide 3.5V which I'm certain would be noticeable and undesired.
    Personally, I would try to use 18 gauge wire (But only if I can comfortable attach this to the female barrel plugs.) I've chosen this based on the 'transmission' column... partly because I am unsure how long the patch cords might be in total, but you can choose smaller wire if you have any ideas or limits on the maximum length that your string of candles will be.

    *I should clarify the use of the 18 gauge wire. This ideally should be the gauge of the wire from the AC-DC adaptor, the gauge of the wire in the patch cords, and the gauge of the wire that connects the female barrel jacks together internally because this will be the 'backbone' that all the current will flow through. Each candle will 'branch' off from this main line, so the wire that connects the actual candle electronics to the power line you are putting in can be much smaller. (You can use the existing wire that was used for the battery pack if you want to keep is easy... Soldering onto existing circuit boards can sometimes be ... tricky depending on the quality it was originally put together with.)
     
  15. sidefly

    sidefly

    7
    1
    Feb 23, 2015
    Sounds great! Thank you so much for the ideas. This weekend I will buy supplies and get started. I will post some pictures of the project so you can share in my joy! :) Thanks again!
     
  16. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    You are very welcome!
    Please include an in-line fuse holder in your supply list!
    Other than that, a little heat-shrink tubing may become quite useful for you, but this should be a pretty straightforward project.
    If you have any questions along the way let us know!
     
  17. sidefly

    sidefly

    7
    1
    Feb 23, 2015
    Where would I put the fuse and how big of a fuse? I'm guessing just before the first candle I connect?
     
  18. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Position. As close to the power supply as possible. If the fuse is close to a candle, you run the risk of having a wire short between the fuse and power supply... this can cause some damage.
    Additionally, the lights won't care if the fuse is close to them, or close to the power supply.
    (That's why you have a large fuse box under the hood of your vehicle. They get a couple main fuses right next to the battery in case something funny happens with the wiring.)

    As far as the size is concerned... This will entirely depend on the normal draw of the lights which we don't exactly know right now...
    It could be as low as 30-40mA per light, to as high as 150mA. With 10 lights this range is pretty wide... 400mA to 1500mA.
    Worst case you pick something too small and the fuse will pop. Simply put a bigger one in next time. If you start out too big, the fuse may not provide fast enough protection for the lights. Personally, I would probably try a 1A fast acting fuse.
    (Ideally, a multi-meter would be used to measure how much a light takes, and calculations would be done on that... but without this, the only thing left is guess work)
     
  19. AlwaysLearning74

    AlwaysLearning74

    2
    0
    Nov 9, 2015
    Hello I saw this post about daisy chaining led candles that ran on 3 AAA and wondered what the final result was? I have 24 candles and want to daisy chain them... all run on the same configuration as your candles.... I need to do this as batteries are way too expensive. Wondering if you could in layman's terms explain (pics would be so greatly appreciated!) how I would link them all to a power ac/dc source for plug into a wall. What type of wire... connectors... fuse and what tpe and how to connect to line... adaptor minimal or max voltage or current. I am extremely capable of soldering (worked in telecom maufacturing production line doing repairs) but just not confident in linking all these lights up And what wires to solder where (which contact points in battery compartment with which wires do I solder)? I hope that you respond or I will spent countless hours trying to figure this out at great cost. I am doing this for my parents as I bought them these candles for their home but they definitely can't afford the batteries nor can I. Thanks to anyone that could help me. Much appreciated! (Hardworking Guy)
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-