220v soldering iron with 120v

Discussion in 'General Electronics Chat' started by Evanguy, Feb 25, 2016.

  1. Evanguy

    Thread Starter Member

    Dec 21, 2014
    81
    8
    so there is a home school group of kids my daughter is friends with, and some of the kids are into arduinos and other such stuff (just getting started i lend a few of them some of my arduino clones last week), they heard me and my daughter were build a radio (im now using tda7000 and tda2003 for it) and they were interested,

    so i offered to make radios with all of them, there is 7 in total, so i went on ebay and ordered 8 of the "diy fm receiver kits"
    since i have gotten a big roll of 1mm solder and made 7 spools of 5 feet long for the kids to use. but i have realized i only have 2 soldering irons, a 25w and a 100w gun.
    i may need a few more, looking on ebay i have found some el chepo ones and since this will be a one maybe two time thing they dont have to be good, im soaking up the colt for solder and irons they are paying me the cost of the radio though.

    i found these, (link below) they seem great for the one time use. but they are 220v 40w,
    My question is if i just plug this into the 120v (north america) outlet will it work at 120v 20w?

    or should i just spend the 5$ per iron and buy 120v ones.

    im looking at one project use, im soaking up the cost,
    7x1.5$ is 10.5$
    7x5$ is 35$
    i hate cheaping out but it may be the best bet now. **if it will safely work**

    http://www.ebay.ca/itm/DIY-40W-Elec...459069?hash=item2eea7b84bd:g:FT4AAOSwYIhWlfPg
     
  2. #12

    Expert

    Nov 30, 2010
    16,345
    6,829
    I don't think 20W is enough. I use 35W for my smallest soldering tip.
     
  3. Sinus23

    Member

    Sep 7, 2013
    163
    411
    This is what we used at school and it could take some strange amount of noobism and still work regardless of abuse and disregard for the property of others.

    But it doesn't work well with lead free solder at that power.

    http://www.antex.co.uk/soldering/lite-range-soldering-irons/30-watt/

    Just a suggestion. I would wait for others to chime in.
     
  4. Evanguy

    Thread Starter Member

    Dec 21, 2014
    81
    8
    i use a 25w for all my my work, http://www.canadiantire.ca/en/pdp/mastercraft-25w-soldering-iron-0586305p.html#.Vs-nrn0rJ0s

    im not sure is 20w would be enough, thats a 20% power difference from mine and mines about the smallest one would want. the soldering in question melts at 181*C

    but i dont want to buy them and have them not work but i also dont want to spend 35$ on them to sit on a shelf for every as spares. but they would be 35W irons, so it wouldn't be the end of the world to have them anyway

    thanks ill see more opinions and then make a decision.
    but in practice they will work but only at half the rated watts if i use half the voltage, correct?
     
  5. Sinus23

    Member

    Sep 7, 2013
    163
    411
    Woah! after looking at your Ebay link in post 1. Are you talking about a soldering iron that is about a 80 cents American per piece before shipping?:eek:
     
  6. Evanguy

    Thread Starter Member

    Dec 21, 2014
    81
    8
    Yeah. i figure its like somthing from the the dollar store. Far from the best but very well may work for very light use.
     
  7. Sinus23

    Member

    Sep 7, 2013
    163
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    True but that price is a bit unbelievable. Check what the others on ebay that are selling the same model charge.
     
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  8. WBahn

    Moderator

    Mar 31, 2012
    17,777
    4,805
    It's doubtful you would get 20 W out of it. If it can be modeled as a constant value resistor (I don't know if it can or not) then cutting the voltage in half would cut the power by a factor of four, giving you only 10 W.

    Now, I've used 7 W irons for small work, but it was designed to get to operating temperature while drawing 7 W. I doubt a 40 W iron will get anywhere close to design temp drawing only 10 W, or even 20 W.

    If they are cheap enough, you can always just buy them and see if it works.

    If they don't, you could get a cheap inverter that outputs 220 V. Even a small one should be able to drive all of the irons you are talking about and having such an inverter handy isn't the worst thing that could be sitting around collecting dust afterward.
     
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  9. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    5,001
    745
    Answer to your half the voltage question,
    NO you will get a 1/4 of the Wattage at half the voltage...

    So 220V 40W iron becomes 120V 10W,
    like you said dont be a cheap skate buy a descent iron...
     
  10. Evanguy

    Thread Starter Member

    Dec 21, 2014
    81
    8
    Thanks guys, i did notice there are about 50 being sold in the price range from 1-2$ so thats the going price for those style ones. also yeah 10 watts seems way too little. ill get a descent one, well seven in this case.


    The 220 inverter would be bad, true but i may just buy better soldering irons
    Thanks for the help guys.
     
  11. Ramussons

    Active Member

    May 3, 2013
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    92
    I have been using a 15 W 220V soldering iron for years. No issues. I'd suggest you try the 40W 220V iron on the 110V supply and see if the solder melts well ( like a 10W iron). That should work for most ods the soldering Unless you are planning to work with High current circuits or Cables/Connectors ...... heat absorbing stuff.
     
  12. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    Sounds like a great time to teach them about "sharing" too..
    "Ok Billy.. You stuff components while Lisa is using the soldering iron"
     
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  13. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Agree with Mcgyvr. If the kids are of an age where they need supervision then the fewer irons the easier that will be. Hopefully you won't have too many burnt fingers and holes in the furniture/carpets :).
     
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  14. Evanguy

    Thread Starter Member

    Dec 21, 2014
    81
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    Thats true, they are boys and girls ages 7-10. so maybe three good 35W irons and they can share and ill also have mine for helping too. good thinking, i dont want a bunch of hot pointy things being waved around everywere. easier to watch over three irons then seven.
     
  15. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
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    Antex do a very popular 15W model - but I doubt it works like that under-running an iron like that.

    The circuitry around the bridge rectifier like in the older ATX PSUs that use a series pair of reservoir electrolytics to make a voltage doubling rectifier. This would work for a purely resistive element - but most certainly not for anything with a transformer in it.
     
  16. SLK001

    Well-Known Member

    Nov 29, 2011
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    A 220V 40W device will only be 12W at 120V. Probably not enough of the watts thing to melt solder efficiently.
     
  17. Tonyr1084

    Active Member

    Sep 24, 2015
    540
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    40 w ÷ 220 v = 0.182 amps
    220 ÷ 0.182 = 1208Ω

    The iron's load (in ohms) is roughly 1.2KΩ

    120 v ÷1200 = 0.1 amps
    120 x 0.1 a = 12 w

    So, putting a 40 watt 220 volt soldering iron on a 120 volt plug will yield a 12 watt solder warmer, nothing more.
     
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  18. ian field

    Distinguished Member

    Oct 27, 2012
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    AFAIK: the element is wound with PTC wire so it is to some degree self regulating.

    When you apply the tip to the work, it takes heat out of the iron - as the PTC wire cools a little it draws more current and compensates.

    This isn't necessary with thermostat irons, so the manufacturers probably don't bother using PTC wire for those.

    A PTC element will try to get up to temperature on half voltage - whether it gets anywhere near can only be found by trying it.
     
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