VGA TESTERS FOR THE children
recently on our Hack A Day forums a member asked about getting some VGA testers made in our “Request and Commissions” forum for a charity called the world computer Exchange, who take old office PC’s and freshens them up to be used by children in developing countries for their education.
I sort of wanted to do a no brainier electronics build as I had been working on that Apple II weather display for quite a while at that point. I say no brainier because I decided to use one of the many already designed vga testers out there and all I really had to do was get it to fit in whatever box we ended up with.
I choose the deogen because it was already featured on Hack A Day, supports multiple raster patterns and resolutions (640×480 through 1280×1024), is already pretty darn small, and uses an ATTiny 2313 which is good because I am already set up for AVR micro controllers. For a case I choose to use some plastic “Ice Breakers” mint boxes, which due to their oval shape makes it quite a bit smaller than an altoids tin. The challenge is on to shove a PCB, switch, 9V battery, 2 buttons and a vga connector in the cramped space.
Join us after the break for a pile of pictures and some build notes.
First up would be the parts. I got most of the required parts from good ole Digikey. There were a few radio shack push buttons from another project, toggle switches from old dead power supplies and the VGA connectors came from a old multiport keyboard / vga switch (one of those with the giant mechanical rotary knobs). including the parts I already had on hand the cost of a pair of these testers would run around 20$, though I got off a bit cheaper.
You can find schematics and a parts list on the main Deogen page, along with a properly laid out dual sided PCB. I wont be using the PCB as I have less space to work with, and I really do not feel like drilling holes, also the micro, power regulator, and crystal were substituted with fairly easy to handle surface mount packages. All passive components are normal through hole with their leads soldered to pads on the board. have you seen a surface mount 18pf capacitor? At first I swore Digikey sent me an empty piece of tape!
The D shape PCB blanks were cut out on a band saw and smoothed over with a table top belt sander, and a test fit is made. As you see everything fits snugly inside of the box. At first I thought I was going to draw this PCB and reality kicked in when I remembered I needed to make a pair. Off to windows and express PCB, where I quickly eyeballed the D shape of my PCB and laid out my design with quite a bit of slack over the rounded part.
I tried toner transfer, and I scrubbed the blanks with nylon pads, acetone, steel wool, and more acetone to get those things clean. I went to my parents house to use my dad’s brand new cannon laser printer. I used the fronts and backs of old fedex shipping label paper and how are my results?
Hatalmas baki! I have never been good at making toner transfer boards but these are by far the worst ones ever. Toner didn’t stick and had a problem with smooshing. The iron I used is junk so it liked to scald the paper and screw up the copper surface. If that wasn’t enough, I didn’t measure the base of the switches which were too wide fit in the 2 holes I left in the PCB. After about the third time of this, I said “well its not getting any better” and I pulled out my little hobby knife and sharpie marker to fix any problems.
After etching, any left over problem areas were gouged out by using a super small chisel that came with a set of soldering picks, while under magnification. Both boards got each trace probed with a continuity meter, then all of the traces are coated in liquid flux in preparation for tinning.
Tinning is accomplished by pooling up a blob of solder on one of the large ground planes and you can simply dip into it with your soldering iron and paint over the traces. It looks a mess because the surface is not smooth caused by excess boiling flux, but one you start soldering on it, it flattens out real quick. I also scrubbed the board down with a toothbrush and denatured alcohol, this is vital or the board is coated in a thick gooey sticky flux syrup.
I soldered the components to the board in my layout. Unfortunately, in my layout, the board is mounted by the push button switches. The VGA connector has to be soldered in after both it and the PCB are mounted, so I need to start on the case.
First, the end is cut to fit the VGA connector. A template was made from a video card mounting bracket taped into place and crudely cut out, and cleaned up with a file. The PCB and battery were set in place and a mark for the power switch is made.While we are in there the (corrected) switch mounting holes in the pcb were used as guides to drill holes into the bottom of the mint box.
Back to the power switch. I measured it with my digital calipers and scribed its foot print in the bottom of the box, it was ttyúk kivágott egy közüzemi késsel.
Ezen a ponton készen állok arra, hogy mindent beépítem a dobozba, de úgy döntöttem, hogy szükségem van néhány grafikára is. HOPPING A Windows rendszerbe, (mert nem tudom elérni a WiFi nyomtató / szkenner munkáját a Linux alatt), beállítottam a dobozomat a síkágyas szkenneremre, és importálta a képet Inkscape-ba, hogy sablonként használja. Vázoltam a grafikámat, és kinyitottam az így kapott SVG fájlt a festékhez tartozó GIMP-be, és kinyomtatta a FEEBEE fotópapírra, amely ragasztott a menta dobozba.
A végső konstrukció magában foglalja először a VGA csatlakozó beépítését a dobozba. Mivel a doboz lekerekített végére a csatlakozó csavaros fülei hajlottak, hogy segítsenek a kontúrnak. Ezután a PCB a helyére csúszik, és most telepíthetem a 2 nyomógombot mind a PCB, mind a dobozon keresztül. Végül a tápkapcsolót a helyére emeljük, és a gorilla ragasztó elég vastag gyöngyjével újra érvényesül.
A végső vezetékezés elég egyszerű EVN, bár nagyon szűkös körülmények között. Forrasztottam a 9V-os akkumulátort klip negatív vezetését egy hosszabb huzalhoz, és a PCB földre forrasztott. The positive lead goes though a diode and into the toggle switch, which is connected to the power input of the circuit. One side of both buttons is soldered to ground, and the other side each lead to a different pin of the microcontroller. Végül a legnehezebb rész csatlakoztatja a VGA csatlakozóból származó 6 sort. Ők; RGB that need to be soldered to the correct resistor dac, h sync and v sync which go direct to the micro controller, and a ground line (which connects all the grounds via a jumper wire on the vga connector).
Adja meg a ragasztót egy kis időt a szárazra, pop egy akkumulátorba, és hátrahagyja a fedelet (amely most az alsó), és jó vagy, hogy menjen! Mindkét Minty VGA tesztelő rémülten dolgozik, és a Deogen Setup nagyon hasznos, ha hibás LCD-t keres. Ne csak vegye be a szót, nézd meg ezeket a boldog táborozókat!
Robbantunk az LCD-nak köszönhetően az LCD-knek köszönhetően! Olyan jól dolgoztak, arra gondolunk, hogy az egyiket több mint 20 másik fejezetünknek küldjük el. Minden hónapban van egy olyan önkéntesek csoportja, akik rendszeresek és néhányan alkalmanként jönnek. Mindenki, akit a csoportképen lát, sok időt szentelt az okig. Mindenki lenyűgözte és elismeri a hozzájárulását