Custom Power Supply

Discussion in 'Electronic Projects' started by Krafter, Sep 11, 2017.

  1. Krafter

    Krafter

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    Hi all. I'm new to these forums.

    I'm in need of a high current DC power supply to power a butt load of RGB LED strips. I've powered them in the past by using old computer power supply's but they don't hold up long after a good nights use at an annual Halloween party. On top of that, I've found it impossible to use a PWM controller as it will shut down the PS after a few seconds. This year I'm wanting to build one that will last. I want one no less than 20 amps at 12 volts. I'm looking at something like this to for the power and this to regulate the voltage. I just want opinions on if this is a good solid plan or maybe even recommendations on something else heavy duty that will last. I really don't want to pay over $150 or so on this project.

    Any feedback would be much appreciated.

    Thanks

    Here's last years party to give an idea what I'm doing.
     
    Krafter, Sep 11, 2017
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  2. Krafter

    kellys_eye

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    kellys_eye, Sep 12, 2017
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  3. Krafter

    Krafter

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    I've never thought about using a car battery for the supply. It does sound like a great idea but I don't think a battery will hold out as long as I need it to. And using multiple batteries would add up in cost pretty quick. I need at least 3 hours of a constant 12 volts to run the LEDs.

    The power supply you linked.... bought a similar one last year. A 25 amp one and it was a waste of money. I'm not sure how they get their ratings but I shut it down almost immediately with only a portion of my strips.

    I'd really like to build one. Do you not think my idea would work? I'd love to hear some feedback on that.

    Thanks again.
     
    Krafter, Sep 12, 2017
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  4. Krafter

    davenn Moderator

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    for the current levels you are suggesting you need, unless you have years of solid electronics experience,
    building one is not a good way to go... it's a VERY significant project


    those look respectable
     
    davenn, Sep 13, 2017
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  5. Krafter

    Krafter

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    Years of experience no. Just hobbyist. I've made a few small projects but you are correct, building one from scratch would be a huge undertaking and beyond my abilities. That's why I was looking at piecing one together which I can do. I was unsure about that mainly because from what I've been reading, LED drivers are switching power supply's and not regulated as I'm looking to build. The power supply's I've used in the past as said in the OP are from old computers, which are regulated and I can't do PWM with them. I was told once that it was because the motherboard does a lot of the filtering from the power supply and I needed more filtering which I've never pursed. But as I found out, they don't hold up long anyway.

    Thank you for the reply.
     
    Krafter, Sep 13, 2017
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  6. Krafter

    kellys_eye

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    Can you power the LEDs in smaller strings to make it a multiple-supply situation or do you want 'all your eggs in one basket' from a single source?

    Given you link to a $300 PSU as a potential solution, what is your actual budget?

    Computer PSU's CAN be used to drive a PWM source - you aren't modulating the 'internals' of the computer PSU, you're modulating the DC output which should be perfectly ok to do. OK, additional filtering 'might' be required but that amounts to a decent electrolytic capacitor (a few 1,000μF at most) at a cost of 'pennies'.

    Computer PSU's are to be had for the asking (your local PC repair shop probably throws out more than you could ever want to use!) and a few of them distributed around the place would solve any supply issue you have.
     
    kellys_eye, Sep 13, 2017
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  7. Krafter

    Krafter

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    I guess in theory I could use multiple PSUs... I've never really thought about that either. Last year I had 5 channels and this year will be similar so I don't see why I couldn't. Maybe I will do some more experimenting before I pull the trigger on anything.

    The first computer PSU that I was used worked great with PWM on the first LED strand or two but as I started added more, the PSU started making a humming sound and the more I added, the louder it got and finally shut it down.

    Question 1: If need be, could I safely add multiple PSUs in parallel to increase the current? I'm sure the reason they don't last long is because I over work them.

    Question 2: With multiple PSUs, I'm assuming I'll have to tie the grounds together since the LEDs will be controlled by one controller (Raspberry Pi). Is that correct?

    And my budget is ~$200. The PSU that I linked above is listed for $109 here in the US.
     
    Krafter, Sep 13, 2017
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  8. Krafter

    kellys_eye

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    Q1. not really - there is no facility to 'balance' the loads.
    Q2. common grounds are necessary as you state.

    If you modulate the LEDs are you quite sure your requirement is for 20A? Have you multiplied out the LEDs per-foot/amperage figures to determine exactly what you need? - although 'more-than-you-need' is, of course, a good way to go.

    Car batteries should still be considered. They negate the requirement for AC mains supplies, can be recharged using low-current chargers (ok, takes longer but after-party, who cares?) and can last the 3 hours you need quite easily. They also don't need trailing leads everywhere.
     
    kellys_eye, Sep 13, 2017
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  9. Krafter

    Krafter

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    Thanks for the answers. Your answer to my first questions agrees with what I've been reading.

    I will still consider batteries. If I do that then I just need to be sure to find something with enough amp hours.
     
    Krafter, Sep 13, 2017
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