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Restrict DC-DC buck to 5v

Discussion in 'Power Supplies' started by deblen, Jun 8, 2018.

  1. Juz89

    Juz89 New Elf

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    Hi, I was looking into the same sort of thing a few months ago but I am by far from being an electronics expert (Just have a love for electronics).After some research online i have found the following crowbar circuit which i added an inline mini ATO fuse to and some screw terminals for ease of use. I was looking into using a SMD poly fuse but thought it maybe easier just using the ATO fuse. I have designed a PCB for this design also but havent gotten around to getting it produced yet and trialled. @AAH or @David_AVD are you guys able to give any input as to if this circuit design will work. crowbar.JPG
     
  2. David_AVD

    David_AVD Bite my shiny metal ass! Community Project Designer Generous Elf

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    Yep, that's the common way to do a crowbar. Since you've done up a design, have you worked out a price they can sell for ?

    BTW, convention is to have input on the left and output on the right. :)
     
  3. Juz89

    Juz89 New Elf

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    This was one of my first designs i played with so it wasn't drawn the best so i am going to redraw it. I reopened it to take the screen grab and thought that doesn't look right at all. I have not worked out price they can sell for as im not good with that sort of thing (Usually go less then i really should). I know what they would cost me to get made but due to not having a reflow oven (Looking at building an arduino controlled one) not sure how long it would take me to assemble them. I have made them using 1206 Package size resistors and the LM431 is SOT-23 so i think it wouldn't be too hard to do with the hot air gun on my soldering station.
     
  4. David_AVD

    David_AVD Bite my shiny metal ass! Community Project Designer Generous Elf

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    For a small quantity, I'd possibly hand solder them.

    For the reflow oven, I use a Kambrook unit with pizza function ($200 unit, not a $50 unit). No need for fancy timing and curves as the heat ramp time is reasonable and we crack open the door once the solder flows and the heat is off.
     
  5. AAH

    AAH I love blinky lights :) Community Project Designer Generous Elf

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    I use the $50 unit I reckon. I do a pre and post heat on the top of the oven and just monitor the boards while they are in there. Once the solder has flowed I swap them out onto the top for a bit of a cool down ramp, swap the next pcb that was pre-heating and then remove the board to a cooling tray.
     
  6. plasmadrive

    plasmadrive Full Time Elf

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    I just saw this thread and thought I would jump in..
    1st off, I have used over 60 Buck converters in my display and I have only had one failure and it just shut down never over voltage that I am aware of. It took nothing out with it. If you don't cheap out and try to use the $1 version you will most likely have great results.

    If you are still sweating the over voltage, you could always get something like a 5 or 10 watt Zenor and put it on the output. The zenor voltage would depend on the protection you want. You could use a 5.6v 2% for example. Personally, I wouldn't sweat it.. I bought all mine from ProDCtoDC and got the potted versions..
     
    Last edited: Jul 12, 2018
  7. Juz89

    Juz89 New Elf

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    For anyone interested i have sent my design off to the board house to get some PCB's manufactured. Once i receive these i will build and test them to make sure they do function as they are supposed to. Once i am happy with the way they are working i will post them up and find out how much interest there is for them.
     
    deblen, David_AVD and AAH like this.
  8. plasmadrive

    plasmadrive Full Time Elf

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    I was asked which I used. Here is a small list on this page.. there are a lot more on the web site and there are also many other sellers. A lot of them already have over voltage protection. They also have over current protection which saves me an inline fuse many times. http://www.prodctodc.com/car-buck-power-supply-c-22
     

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