Taking on the task of building a machine in a customised case is not without it’s challenges. As I soon discovered when I came to designing the front of the machine. With six LED’s, two switches and one illuminated power button. I had plenty to fill up the flat blank looking facia. But how was I going to go about it? I knew I wanted lettering under the various lights and switches to indicate function. But how exactly was I going to do it, without it look awful. Someone with money to burn, might have paid for chemical etching or some method that paints the letters on. On a budget I faced using a label maker and sticking labels on to the front facia. This was definitely not the look I was aiming for. The Altair had a wonder front to it and I wanted something similar.
It was then when I had an idea.
Placing the front panel under the flatbed scanner, I made a reasonably high resolution copy. I then loaded the image up and began designing where all the LED’s and switches would go. Having already sketched a rough design out on paper, with measurements of the panel and the components. I had a pretty good idea where things would be installed, which meant building it on the computer was fairly straight forward.
Printing a template out on my laser printer, I cut it out and taped it to the plastic panel. Then using a dremmel and a drill piece, I bore out holes for all the components. The LED’s where the trickiest part, make the holes to large and the LED’s would fallout, the fitting needed to be snug. With the holes made, I used a file to clean the panel up and removed the paper template. Offering the switches and light up, I found more filing/drilling was needing. So back to the dremmel I went.
It took a good hour of fiddling before all the components slipped in to their designated openings, but soon it beginning to look Altair-ish. I wont deny a sense of pride filled me, when I saw the front panel with all the components sitting in the case for the first time. Up until that point, the project had felt more a less like a pile of components. So seeing it come together for the first time was pretty satisfying.
With switches and light installed, I used a hot glue gun to secure the LED’s. With the wiring I know the chances of them falling out would be inevitable.
The next step was the actual facia or cover. Now this was the clever bit which I mentioned earlier. Having made a template on the computer, I had also incorporated in to the template all the various labels. Printing out another copy, I cut the out the holes for the LED’s and switches and offer it up to the front panel. Almost all the components pushed through the holes where they should. But several of the LED’s did not line up. As I had been cutting out the holes by hand with the dremmel, I guess I should be pleased at most of them aligned at all.
Taking measurements I went back to the computer and altered the layout, spacing the LED’s farther apart. This took me several attempts and many templates before I finally had one that worked. Finally with all the parts pushing through where they should. I was ready for the next stage. Making a final panel cut out, using thicker, high resolution card. When the printer spewed forth the finished version I saw a problem. Unlike normal paper the high resolution card had given the black ink a gloss look. With no way around this, I took a leaf out of my prop making skills and made a gamble. Using some Matt varnish spray I use for for water sealing decal paper. I sprayed the facia with three coats, with 4 minutes between coats. I then used a hair dryer to gentle dry the varnish. After 20 minutes it was dry to touch and had to my joy given the printed panel a Matt finish!
Using some 3M adhesive spray, I mounted the facia to the front of the case. Definitely heart in your throat work, as fowling up at this stage would have meant a big mess. As it where, it went on without a hitch.
One thing I was aware of when making the cover, was the need for it to be 3-4mm smaller then then actual plastic panel. As the panel it self, slid inside channels cut out along the front of the bottom and top sections of the case.
With the card attached the panel would have been to thick to fit. As the facia only needed to cover the visible surface of the front panel, it wasn’t much of a problem. Thou when the lid finally did go on, some trimming was need before everything went on properly. Even the best laid plans can run fowl!
Above is the circuit I built for the purpose of powering the LED PCB. At the heart of the circuit is a LM317 adjustable, three terminal regulator.
Initially setup without a 20 ohm resistor in line with the voltage out. This amendment to the circuit was needed to control the current feeding in to the PCB. Which caused the first setup to overheat and fail. In plain English, the microchip on the PCB melted, well near enough!
For the correct voltage to output from the circuit, the values of resistor’s R1 and R2 had to be determined. As my maths is terrible, I cheated by using an online calculator to figure out the necassery values. Which turn out to be 120 x 150 = 2.81 Volts. This was under the 3v given to the PCB by the 2 AA batteries that originally powered it. But given batteries are a constantly depleating power source, I did not think feeding a constant 3 volts in to the PCB would be healthy in the long term. Which is why I choose 2.8v.
I have to say that when it came to making this circuit, I found it quite a challange. I’ve always had a love for taking things apart, rebuilding them. But that has always been easy to me. It’s like working on a three dimensional jigsaw, where the pieces are components, which all slot together in a specific way. But making a circuit from nothing, this was something else, especially as I did not fully understand circuit diagrams and symbols. Luckily consulting several people online via IRC, proved the most useful thing I could have ever done. It is thanks to those individuals i was able to understand what i was doing and actually turn a rough diagram in to something that functioned.
With it completed, I connected a universal PSU outting 3v 1.5mah and tested the regulator. Nothing, the thing had zero output. except from when i hooked the voltmeter to the V in and ground. So something was wrong. I had nothing coming from the V out and Adjuster. While to this day I’m not sure how it happened. R2 somehow became perminently open, perhaps it was a faulty component, who knows. But for the cost of a few pence, i wasn’t really bothered. In addition to this, i had the feeling that my brief fight with a stubborn soldering iron, which refused to get properly warm. Had resulted in the regulator being damaged. In the end, I bought full set of replacement components. Using my dad’s older 70’s soldering gun, yes a gun with a trigger. I was able to fit the replacement parts in minutes. Honestly i dont know how i’ve managed so long without having this tool, compared the standard wand iron i have. The trigger iron, applies heat when you need it.
With the new components in place, i tested the circuit and discovered huzaar 2.8volts!! When i saw the reading pop up on the multimeter I was relieved. As i was sure the reason for the fault had been something i had wired wrong. But no, the circuit layout as it turned out was good.
With the circuit tested, I set about putting all the parts together within the case. The end result was a rather full looking box of wires and parts and myself looking ever more worried something would surely come loose.
Switching from the universal PSU to the internal mini ITX power supply did not strike me as anything that would set off a red flag. Having taken in to account the 12v and 5v feeds, I had already worked out that i would steal power from a redundant HDD molex connector. When the machine powered up, it was on the kitchen side. Everything worked! Leaving the system on while I went for my camera up stairs. I thought five minutes turned on would tell if everything was working. I couldn’t have be more correct. On my return i noticed one of the LED’s was nolonger working. Flicking the switch, it came back in to life, while two others had died. Placing my hand over the microchip on the LED PCB to check the heat, the hot glue covering the chip stuck to my hands. It wasn’t warm, it was cooking! Powering down for 10 minutes and then back on, revealed the PCB was indeed cooked beyond repair.
It was at this point i realised something i had overlooked, the current! the universal PSU had a maximum output of 9v 1.5mah. But what rating was the Uniross adaptor i was now using to power the entire system through the ATX power connector? A lot more then 1.5mah.
A great deal has happened since my previous post regarding the mini ITX computer. While I am not always able to post upto date photo’s of the project as it is happening, I am making every effort to keep posts relatively fresh from the press 🙂
Since the last blog the little machines has come along in leaps and bounds, the front panel is complete along with LED’s and switches. One issue has been how the tiny PCB that drives the LED’s will be powered. Originally I had it in my head that there was a 3 volt feed available from the ATX power supply. Sadly I discovered i was mistaken, i actually had 12v or 5v to choose from. Not promising when working with a fragile circuit that was originally intended to run from 2xAA batteries. So began a search to reduce the DC coming from the PSU, this eventually led me to regulators, specifically variable regulators, which are capable of reducing a 5v feed to as little as 1.5volts. At first i attempted to construct my own 2.8v rated regulator, using an LM317 and two resistors. As i have never done anything like the before, i found my soldering, indeed my knowledge of circuits coming under pressure. However after consulting several people on the subject, i pressed on and succeeding in a prototype circuit. As is typical for my luck, it did not work. Why, has yet to be determined, but the most likely answer is the regulator was damaged while i was struggling with a faulty soldering iron.
I have subsequently purchased another set of parts to attempt another build. If there is one small mercy out of all of this toil. It is that my work was checked by Thrashbarg from the Vintage computer forum and given the ok. Hey my soldering isn’t as bad as i thought! just a pity the damn thing doesn’t work!
While i shall work on getting it operational, I have already formulated a backup plan, involving a power supply kit which can be purchased from Maplins. The k18231a requires assembling, however the quality of the kit is far better then the one i am building. With an integrated potentiometer to adjust the output to your requirements, over all i feel this PCB is better suited to the task of powering the front panel LED’s.
Assuming i get the front panel operational, the next step will be to get the machine working.. I originally intended a CF card to be used for storage, however from first hand experience, i discovered they do not always lend themselves towards booting with an active partition on board. Whether this is something that can be fixed i had no idea. If not, i shall had to investigate the possibility of an internal 2.5″ hard drive.
Circuits aside, I was truly pleased with how the front panel graphics came out. No before you ask, i have not had the white lettering etch on. In fact what you see, is a sheet of gloss card with a front panel template printed on and placed over the original black plastic fascia. This was to me the only way to get the front done without going to ridiculous expense. After spraying the panel with matt varnish, the graphics lost their overly gloss look, which was much to my relief 🙂