101 lines
4.8 KiB
Markdown
101 lines
4.8 KiB
Markdown
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date = "2014-11-26"
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title = "VoltMeister 100: Bench Power Supply - Part 2"
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tags = ["electronics", "voltmeister", "power supply"]
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categories = [ "Electronics" ]
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description = "In Part 1 of this series I discussed how an ATX power supply can be usedto create a poor man's bench power supply. In Part 2 I'll show you howI managed to fit the ATX power supply, my control board and everythingelse neatly into a single box."
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slug = "voltmeister-100-atx-bench-power-supply-part-2"
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In [Part 1](https://ariejan.net/2014/11/24/voltmeister-100-atx-bench-power-supply-part-1/) of
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this article I've discussed the design and PCB layout for my _VoltMeister 100_ project.
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I've converted an ATX power supply to a safe-to-use bench power supply. Although not ideal
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for anything serious, it's a great way to actually get started and complete a project.
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This is Part 2 of a two part write-up of how I designed and built my first bench
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power supply.
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* [Part 1 - Design, schematic and PCB](https://ariejan.net/2014/11/24/voltmeister-100-atx-bench-power-supply-part-1)
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* [Part 2 - Enclosure and finished build](https://ariejan.net/2014/11/26/voltmeister-100-atx-bench-power-supply-part-2)
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## The enclosure
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I think that in a professional design process there is some tension between the PCBs you design, the
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components you use and the enclosure you need to all fit it in. I tried to be smart and opted to buy a
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'universal enclosure' that would fit my ATX power supply and leave some room for a small PCB.
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Because of the dimensions of the ATX power supply (roughly 140x50x80mm), I needed something that would fit that.
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Note that most dimenstions specified when shopping for enclosures are _outside_ dimensions.
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In the end I opted for a nice Hammond enclosure, large enough to fit my power supply snugly and not
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too expensive. It even has nice aluminium front and back panels. For those wondering, it's
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the [1598ESGY](http://octopart.com/1598esgy-hammond-46506) from Hammond.
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![](/img/hammond-enclosure.jpg "Hammond Universal Enclosure")
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Another thing I learned is to take a detailed look at the specification drawings.
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![](/img/hammond-inside.png "Inside the enclosure")
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Notice the two supports circled in red? Yeah, those are used to screw the top and bottom parts of
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the enclosure together. And guess what, my ATX power supply does _not_ fit between those
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two supports and is now protruding about 10mm from the back. Booh!
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This is really a problem. I don't want to have an ATX power supply hanging out of the back.
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At first I thought of just buying a larger case, but I would not be that easily defeated.
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Because I'm curious by nature, I opened up my ATX power supply to see what's inside and
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remove some of the cables I would not need.
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The PCB for the ATX supply is pretty tightly packed, but I noticed that transformer on the side was
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not mounted on the PCB. There was a nice cutout on the PCB to allow room for the transformer.
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Putting one and one together I decided to remove the ATX enclosure and see if I could fit
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the PCB in my small Hammond case. The transformer could be moved just a bit so it would
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not interfer with the support inside the case.
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This worked brilliantly. All I had to do was make cutouts for the powercord and 120/230V
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selector.
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The only reason I did this is because there is a clear separation between the high
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voltage parts of the supply and the control (for the fan, I presume). Because the
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orientation was just right, it would also shield my own PCB nicely.
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## The build
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Here you can see the inside of my bench power supply.
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![](/img/case-inside.jpg "Inside the case")
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The bottom half is filled with the ATX PCB. You can see the ground wire floating around,
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this has been connected properly tot he front and back panels.
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The transformer is leaving a bit of a gap and has been placed just on the other
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side of the support.
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On the top you can see my PCB with the ATX connector attached to it and wires going
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out to the LEDs, the power switch and the different output voltages.
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## The result
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And, this is the end result. Suffice it to say that my precision drilling skills need
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some more love. But other than that, I'm quite happy with how it turned out. It's my
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first project, after all.
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![](/img/voltmeister-100.jpg "VoltMeister 100 in all it's glory")
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## Conclusion
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Building an ATX-based bench power supply like this is nice. If you need
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a stable and reliable power supply, you're probably better off buying a cheap
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linear power supply online for like € 50.
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I did this project to learn something. And I did. I learned how to SMD solder components,
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I learned what to look out for when selecting an enclosure for your project. I also learned
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about ATX power supplies and how you don't want to mess with them. These units handle
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pretty beefy currents. If you don't know what you're doing you could end up hurting yourself.
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What's next? The VoltMeister 200, of course!
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