Posted on Apr 1, 2017 in enclosure, hardware, laser chopping, power
In my final article I built a controller board across the Artesyn NXA66 server power supply module that I picked up very cheaply on ebay. This board gave me the power to regulate the important thing features of the module and shaped the idea for a fairly good, excessive current desktop PSU for voltages of three.3 or 5V with the power to modify out the module for a three.3V/2.5V module if I so desired.
To finish off the undertaking I made a decision to make a case for the controller board with typical switchgear and sockets for the entrance and rear panels. This is the writeup for that venture and there’s an associated YouTube video you can watch as properly.
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Earlier than I can design something I have to know what it’s that I’m going to design so these are the essential specs for the case that I’ll be constructing.
- 4mm entrance panel jack sockets for power output.
- Front switches for output-enable and degree selection.
- Front rotary encoder for options choice.
- Rear 2.1mm input for 12V supply.
- Rear on/off change.
- Rear DB9 connector for RS232 knowledge logging output.
- Rear 4mm jack sockets for load voltage sense inputs.
- Aspect mount 40mm cooling fan adjoining to NXA66 module.
With that in mind it’s time to determine upon the fabric that I’ll use.
The apparent selection for a hobbyist corresponding to myself who doesn’t (yet) personal his personal CNC machinery is laser-cut acrylic because of the convenience with which it can be minimize for me by an internet service. I additionally want a minimum of some a part of my case to be clear in order that the massive LED displays mounted on the PCB are seen from the surface.
So acrylic it is. It’s a cloth I’ve used before when designing the case for my reflow controller so I’ve at the very least a naked minimal of familiarity with the fabric.
This time I’ve decided to go for a transparent neutral gray colour because I recall that in the course of the YouTube video for the controller I used a small piece of transparent grey perspex to filter the LED shows so that they showed up on the digital camera. It seemed really nice and clear so I’ve determined to go forward and use it for the entire case.
The final choice to make is the thickness. The web providers supply 3mm and 5mm. I selected to use 5mm for the reflow oven case because it was fairly giant and I needed to scale back the prospect of it flexing. It’s a must to watch out when choosing thicker panel supplies because the shafts of most of the switches and notably cable glands (in the event you’re using them) might not have an extended enough thread to undergo the panel and depart sufficient thread protruding to attach the locking nut.
This time my case is smaller in measurement than I made earlier than so I’ve chosen the 3mm thickness. Let’s hope it really works out favourably.
The service that I exploit to get the supplies minimize have to be selected earlier than I begin designing as a result of there will probably be some constraints I’ve to abide by, for example:
- The template measurement. They are going to be shopping for in sheets of uncooked acrylic and I’ll want to fit my design inside the measurement that they offer, in all probability even on a template file I can download.
- The laser kerf measurement. They’ll inform me the diameter of the laser beam that does the chopping and I’ll need to use this to calculate offsets from the perfect positions of elements of the case which might be meant to suit snugly collectively. This is essential.
- The colors and widths of strains in the design that I’ve to make use of to point areas that must be minimize and areas that must be engraved.
Final time around I used RazorLab within the UK for the slicing service. It labored nicely and so I’ll be utilizing them once more. I downloaded their ‘P2’ template and obtained started with the design in Inkscape.
Inkscape is a freeware drawing program that I used last time. It has a considerably clunky UI, it’s definitely no Illustrator or Corel Draw, but I want only a small subset of the performance to create a case design and it’s not arduous to study. It doesn’t maintain me up or cause me to curse the display so I’ve no drawback recommending it for this objective.
Designing the tabs used for the case closure is a laborious and repetitive activity so to get me off to a headstart I used the MakerCase website to supply the initial outline. I exploit the T-slot option to create a design that features captive screws to hold the case together.
The finger joints hold the panels within the right position relative to one another and the captive screws within the T-slots pull them together in order that they don’t crumble.
Whenever you save a design from the website it asks you for the laser kerf width. It’ll use that width to shrink again the minimize strains with the expectation that the width of the laser will spill over from the center line sufficiently to make a cosy fit.
Final time I used a setting of 0.2mm and, while I might get my case together, it was very troublesome and I had to apply silicone oil to get the finger joints to return together. This time I’ve lowered the kerf to 0.1mm to permit more beam spillover and hopefully a neater fit that’s not too unfastened. That is the type of factor that you could solely study from expertise.
Now with the essential case panels created I want to add the cutouts and engravings.
All of the bits and items I want have been ordered from ebay so it’s just a matter of getting the calipers out and measuring the sizes of the holes that I want after which positioning those holes evenly at one of the best place on each panel.
I don’t essentially comply with a scientific technique of doing this. I take a greatest guess at where I feel the holes are going to should be and then I’ll print out the design 1:1 on a bit of paper and use scissors to cut out the panels. Then by providing up the controller board to the mock panels I can accurately measure how far off I’m from the place I assumed I’d be and make the required corrections earlier than doing one other spherical of printouts.
Click on to download unique SVG. There’s a second design for another, unrelated case at the prime of this graphic.
Lastly I’m ready to add. The worth charged is predicated on a flat fee for the piece of acrylic and then a variable charge for the quantity of laser time that will probably be used to do the chopping. You possibly can add and check your design at Razorlab’s website as typically as you wish to see how much it’s going to value earlier than you submit it for making. Keep in mind that the fee quoted is before supply and 20% VAT.
The flat price for the acrylic is pretty low and I’ll burn up most of my value on the chopping time so it pays to optimise that as much as I can. Finger joints and T-slots require various chopping so the MakerCase website does try to optimise by putting panels back-to-back the place similar cuts could be merged into one.
I can optimise a bit of myself by decreasing the number of finger joints to the minimum required and, since I have one other PCB for a unique design that needs a case, I will embrace it within the unused area. It’s a balancing act between the fastened value of the acrylic and the additional value of spending laser time on utilizing up unused area.
Razorlab have been very quick this time and I received my bits again inside every week at a total value of about £40 together with VAT and delivery. It’s fairly costly relative to the cost of having ten PCBs made in China however nonetheless much lower than anyplace else I’ve seen.
All the items are wanting very nice and a quick verify reveals that my selection of the gray clear acrylic is an effective one because LEDs show by means of simply.
A number of the elements had bits of the protecting movie missing however I’m completely happy to say that there have been no scratches, just some areas with some glue residue that was easily eliminated with some white spirit.
The first thing I checked was that the finger joints would slot collectively. Making an allowance for the issues I had final time, I was actually hoping the lowered 0.1mm kerf setting would repair it. I’m pleased to say that it did. The panels slot collectively nice and straightforward with no lateral play at all. zero.1mm is the right setting for kerf at Razorlab.
Next up is to make it possible for the switchgear match within the holes and this is where I hit two snags, both of my personal making. Firstly the power change doesn’t quite match alongside the long aspect.
It’s really very, very close; much lower than a millimeter and I’ve no concept how it happened. I measured it with calipers and I’m positive I added somewhat for security but I assume not. The laser minimize gap matches my design so it’s all my fault for positive.
The opposite drawback is the anti-twist notch on the rotary encoder. It’s presupposed to mate with a small gap on the case to stop the encoder from twisting around the case.
The case gap for the notch is just too small. Again it’s a tiny distinction and this time I’m scratching my head as to the way it occurred because I did a copy-and-paste from my reflow oven design on to this one and someplace alongside the best way the opening received smaller. The only factor I can consider is that I should have had the opening by accident chosen in Inkscape once I utilized a change or pressed a key mixture that did a resize as an alternative of a move. Once more, consumer error.
Both of these errors might have been spotted with a extra rigourous QA examine before importing and that’s one thing I’ll be doing sooner or later. Anyway, for now I can fix these issues fairly easily.
I fastened the change drawback through the use of a dremel on excessive velocity to very gently shave the case hole just a little bigger. Within the video that accompanies this article I recommend that I’d shave the change as an alternative but I tried that and the plastic appeared to be the sort that may quite soften than shave so I gave up and gingerly tackled the case as an alternative and it worked out effective.
The encoder notch was simply fastened through the use of a dremel to shave the notch in order that it’s somewhat slimmer. It’s made from some low cost and gentle base metallic that simply gave solution to the dremel.
Finally I can now assemble it.
It took one of the best part of a day which was just a little longer than I assumed it will. It might have been simpler if I removed the PCB terminal blocks and soldered directly to the board however I opted to go away them in case I ever needed to carry the board again out from the case.
Fats 2.5mm wires are used to connect up the incoming power source. Strong core hookup wires are used to connect the load sense inputs. The UART connections go to an affordable UART-to-RS232 board that I obtained on ebay. This got here as a package of elements that I needed to assemble.
The entrance panel has a pleasant balanced look with the encoder knob in the middle, the power outputs on the left and the switches to the proper. I already had clear acrylic screws out there so I used those for the case fastenings. Initial misgivings concerning the constrasting color of the screws have been misplaced because I feel it seems very nice like that.
The female DB9 connector for the RS232 output screws into the case leaving sufficient area for the shroud of the cable to fit in and absolutely mate with the pins. I had some considerations concerning the proximity of the screw holes to the connector opening however it does seem to be OK.
The fan opening is designed to be right by the power MOSFET on the module which should be the primary source of warmth. It’s a Gelid Silent 4 that looks nice in white. For consistency I used the identical clear acrylic screws as all over the place else and ran the connector beneath the board and back over the left to keep it tidy.
A set of four 3M Bump-ons full the case. Should you never used this stuff before then I extremely advocate them. The rubber compound that they use is extremely tacky, simply preventing the case from sliding over your workspace once you operate the controls.
I stored testing it throughout the assembly. There’s little point in absolutely assembling it only to understand that one thing doesn’t work that may require it to be all taken to bits again. Once I finally came to shut the lid I used to be assured that it will work.
Here’s a photograph of it operating. The effect of the clear grey case is to attenuate the glare from the LEDs in order that the digits turn out to be very clear to learn and you may’t see the inter-segment elements in any respect. Should you’ve ever used these seven-segment LEDs before then you definitely’ll know what I imply concerning the readability and over-visibility of the fabric used to separate the segments. I extremely advocate this material as a filter for seven-segment LEDs.
The rear power change has a built-in 12V green LED that looks good glowing behind the case.
Regardless of a few utterly avoidable operator errors I did take pleasure in spending a day putting this case collectively and the result is that I’ve a accomplished undertaking that I can and can use in future.
I shot a reasonably brief video of the meeting course of. For those who’d like to observe it then click under, or higher still open it on the YouTube website to view it in a lot better quality.
Please be happy to go away a comment under or should you’d wish to ask a extra detailed query and begin a dialogue then do please be a part of the forum thread.