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Online DIY (0 - 30V, 2mA - 3A) Power Supply Kit

Discussion in 'Power Electronics' started by Old Grey, Feb 5, 2016.

  1. Old Grey

    Old Grey

    26
    2
    Feb 5, 2016
    DIY Kit Current Limiting (0 - 30V, 2mA - 3A) Continuously Adjustable DC Regulated Power Supply

    http://www.gearbest.com/development...62rEZG06prA1yyxc8ZuBBK7EaQUItzM0EgaAmMp8P8HAQ

    This online kit looked good at only $15 - it looks pretty good and is way more than I need -.
    But when I started looking at all the extra hardware, transformer, panel meter, case, heatsinks, etc, it soon blew out to over $50 - way too much for what I need -.
    But after I opened up a blown ATX PS - caps -, I noticed all the hardware I need to finish the kit was inside for free. The gutted ATX case has a 12V fan, 240V connections, 240V switch, case, heat-sinks, and what I think is a filter - cap and inductor - soldered to the inside 240V socket, so it's practically ready to go.

    The kit needs a 29V 3A 240V transformer, but I only need something like 12V 1A, and looking inside the ATX PS there is a large-ish EI-40c transformer.

    I can't find an accurate datasheet, so I don't know if it will be suitable.
    Maybe this
    http://www.kondzio.info/images/artykuly/2015/transformator-impulsowy/EI-33-datasheet.pdf
    http://chipsen.en.made-in-china.com...a-EI40-Current-transformer-specification.html

    Here are some pics
    https://www.mediafire.com/convkey/c141/4uva5mjt899iyto6g.jpg https://www.mediafire.com/convkey/edff/z66lnkp4g9f05jd6g.jpg
    https://www.mediafire.com/convkey/5cfc/snsaot1xhjknz3b6g.jpg

    I removed the EI-40c, and it has 3 legs on the input with the centre one cut - I presume it's for 110V -, and the output has 6 pins and a large common. Do you think I can use this transformer?

    Any advice would be appreciated. Thanks
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,178
    2,690
    Jan 21, 2010
    It wont be suitable. The transformer(s) in the PC power supply are designed for high frequency use.
     
  3. rickselectricalprojects

    rickselectricalprojects

    118
    12
    Feb 1, 2015
    I also wouldn't use the caps from the broken atx power supply, there values have probably been effected.
     
  4. rickselectricalprojects

    rickselectricalprojects

    118
    12
    Feb 1, 2015
  5. Kiwi

    Kiwi

    313
    71
    Jan 28, 2013
    "I only need something like 12V 1A"

    Why not just get a 12v adapter?
     
  6. Old Grey

    Old Grey

    26
    2
    Feb 5, 2016
    Ouch!
    Some of the online info said it might be high frequency, some said current transformer - not that I would know the difference because I'm low level new -.
    Just doing some quick reading it seams most stuff is now changing to HF. How do you even know what you are buying, and can you spot the difference.
    I've got my cheap DSO138 running, will I check it, or is it 100% HF.

    All the other online stuff won't go below 1.4V, and I need semi accurate adjustability down to 0V, like a lab PS - I'm making a AF meter for narrowband lambda 0 - 1.0V -.
    I'm getting a bit into electronics because I want to build the Arduino based EMS (Speeduino) - that's all I can afford -, so a cheap lab PS might be handy.
    The kit has current and voltage adjustability, something a AC adaptor doesn't, and a better range than anything else that's cheap - no income -.
    Currently I've just been using a pot with batteries, but for $15 it would be a cheap step up.

    I think that eBay thing is a buck converter with display, and I don't think it can go below 1.2V
     
  7. rickselectricalprojects

    rickselectricalprojects

    118
    12
    Feb 1, 2015
    If you want a bench power supply getting that kit is probably the cheapest and most reliable way of getting a bench PSU as the cheap $70 eBay ones are very low quality.
     
  8. Old Grey

    Old Grey

    26
    2
    Feb 5, 2016
    It's been hard finding info about HF transformer cores, so it's taken all day, but it looks like in a ATX PS they increase the frequency of the 204V 50Hz before the transformer core, so that the actual core will be a lot smaller and cheaper.

    I don't know what will happen if you do use a HF core in non HF circuit, but I think that means that the core will be out of it's optimum operation spec range, and will not work very well.

    I still don't know how to spot one from the other, but it seams unlikely that modern equipment would have something you can salvage that isn't HF.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,178
    2,690
    Jan 21, 2010
    That is pretty true. Connecting one of these high frequency transformers to the mains would result in a blown fuse. If you didn't have a fuse you'd end up with a lot of smoke.

    One simple approach might be to find a laptop power supply with an appropriate output voltage and use that as the input to your regulator. It will mean you don't have to play about with mains voltages.

    Common laptop power supplies are rated for several amps at voltages around 19V. This would allow you to easily provide a regulated 12V output, and whatever else the regulator does.
     
  10. Old Grey

    Old Grey

    26
    2
    Feb 5, 2016
    I was at the junk sale and found a 13.5V 1.5A power pak that is heavy like a brick, and just about as big, for $3.

    It's got an iron core transformer and 8 components, and because it's simple inside I guess it's what I'm looking for.

    I talked to the Youtube guy and he reckons a 12V AC transformer will be a 17V PS with the kit.

    DIY Kit - $14.30
    Panel meter - $3.63
    10 turn 10K pot - $2.06
    Transformer - $3
    terminals - $1.50
    Other parts from ATX PS - free

    For $24.50 it looks like a plan.
     
  11. supertech007

    supertech007

    5
    1
    Feb 28, 2014
    Check MCM electronics they have nice units very cheap and good quality
     
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