Sunday, November 30, 2008

teaser pics

Just getting an idea how things will fit inside, thought it's a good progress post.

building the channel strips - pots

This covers the upper section of the channel strips - the pots. I decided I didn't want to mount my pots on the front panel and saw another user design where he used clear perspex to internally mount layers of components - I liked this as it added a challenge and should look nice and be easy to work on. Therefore I needed to drill 64 holes (plus another 64 guide holes) for the 8 pots per 8 channels. I gave this a shot myself as I had the perspex sheet ready to go.
*doofus alert*
I cut and sanded the piece to size and marked out my gridlines with a ruler. What I failed to do was use a set-square instead. Perspex can sometimes grab and crack when tooling and I had good drill bits but you need a proper bit (dowling bit) to do this the pro way, which I didn't have. Therefore I had to clamp the bastard for each hole - a grueling task that took me 2 nights to finish and a sore back. When I drilled the last hole, brushed it off and held up a set-square the holes were all off - some up to 2mm off in random directions - not very happy at all, but had learnt some lessons. In the end I decided to outsource this part as the cost was not too high and I wanted to keep things rolling. A few days later my plates were ready and it was time to drill the smaller guide holes and bolt in the pots.

My pots (and most do) have a small tooth that juts out so it can be fixed and will not slip or spin around when you turn the knob to it's extremes. I drilled these myself with a 3mm drill and it didn't take long after I ruled my gridlines, this time with a SETSQUARE! Again the fangled laser guide feature on this drill press came through as quite a cool feature - go Ryobi!

All drilled and ready to bolt in the pots. The upper plate seen is for the master section which I'll do later.

Crap - that's a lot of pots!

I followed these instructions for wiring the pots. I used wire-wrap for the 5v and ground connections and made this little module to act as a connector mount.
Advanced soldering techniques :-)

You can see how I did the wire-wrapping here and get an idea of what a sizable task this was to complete - an entire weekend worth - thankfully the 3 day test cricket was on so I kept my brain awake by listening to Australia kick the Kiwi's asses.

I'm convinced that I chose the WORST possible solution for connectors, but anyway, you live and learn. Don't use these they are so laborious - use IDC headers or others.

Fly cables made and fitted and we're done and dusted - again I was pretty stoked with the end result, but I seriously thought this one through and took my time with it.

building the channel strips - switches & faders

There's 2 parts to the channel strips - the switches/faders (lower section) and the pots (upper section) - this covers the lower section. What made this part real easy was using strip-boards. Otherwise known as vero-boards or matrix-boards they are copper etched PCB's with holes pre-drilled in a grid with standard size and layout. Commonly used for prototyping, they usually have copper strips or dots so all you need do is fit your components, solder them in place and you have a nice straight square layout without having to tool anything.

Cut and sand the 4 boards down to size and drill holes for the mounting pins on the faders.
Solder the faders in place, then snap in and solder the the tactile switches. In order to cut the copper tracks where needed I used a Dremel because I already had one and it was easy, you could use a razor, file or I'm sure there's expensive overpriced tools made for the task too.
Finally solder the grounding wires for the switches using wire-wrap then make and fit the fly cables for connecting the switches and faders to the MB modules (AIN & DIN).

I was pretty happy with the end result and didn't make any screw-ups which was awesome.

Thursday, November 27, 2008

building the housing

When you look around some of the ideas punters are coming up with for their MIDIBox projects it's inspiring to say the least. I decided that rather than mod my old C64 case or gut an unused CD DJ mixer deck I wanted to build my own housing from scratch. Keeping things simple and cheap, I found a bunch of aluminium angle strips sold at Bunnings that would do the job. Aluminium is a great material as it's cheap, strong, light-weight, conductive, safe & easy to work with and readilly available. My design was going to be a flat rectagular tablet, which I might later annodize or powder-coat to black for aesthetics. First would be make the rectangluar frame from anlge strips, then add a plate for the base and a plate for the top panel. When I get to that stage and if I still have any money left, I might get all the holes and etching in the top panel professionally done (for what I expect to be a hefty fee).

Just getting an idea of how the frame will fit together.

Clamp and cut the angle strips to length, then flush off on the disc-sander. This leaves the edges perfectly straight and square.

Finish off the sanding with some wet and dry.

Clamp 2 pieces so they meet in a corner and are square, then drill the guide holes for the self tapping screws. The laser guide on this drill-press turned out less of a gimmick than I thought.

Because I want a nice flush finish for the screws it's time to rock out the counter sync bit.

Nice....nice and uhh, counter-sunk.

Tuesday, November 25, 2008

selecting components - pcb stripboards

For the channel strip modules and other PCB requirements I decided to go with stripboards rather than matrix boards, mostly because surprisingly I couldn't find a supplyer who stocked a matrix board with actual 1mm holes (they all say they are but when I ordered them and tried to fit the snap-in switches they wouldn't fit, and there was NO way I was going to drill out a few hundred holes as a work around. Stripboards were also fine because I could use the Dremmel to finely slice through tracks as needed, use wire-wrapping wire still and I found some good size very cheap ones from WES Components which ACTUALLY DID have 1mm holes (part#PCB119).

selecting components - switches & leds

I wanted to get some of those nice tactile LED switches you commonly see in audio mixing desks but I when I saw how much the switch-pimps deal these out for I nearly keeled over. Seriously - most of these sell from $5 up to $10 EUR a piece - so in a typical small to medium size mixing desk you are likely to have at least 50 of them (I need 128), are you REALLY expected to spend $200-$500+ just on switches??! Wake up you retards these things are made in China by the millions and cost cents per unit to manufacture so it's obvious this is just a capitalist scam.


So after a few days rethinking and redesigning I came up with a really cool way to do what I wanted that was extremely cheap - take THAT switch pimps! I ended up finding a nice and simple low-profile ALPS tactile switch that sits perfectly on the channel strip modules and some nice cheap RGB LED's that also suite perfectly. My design, inspired by this, was to make my own fancy button tops out of 15mm semi-transparent white acrylic cubes and mount the LED's inside them , then glue them on top of the tactile switches, should look great. Also this way I don't need to additionally cut holes & mount the 128 LED's which will save time and money and keep the design simple and sexy. It does add a little additional work making the buttons, drilling the holes, filing the LED's down and gluing them on the switches but this is the whole fun of DIY and I know it'll be cool fun. I sourced the parts from Switches-Plus who were very helpfull and took the time to steer me in the direction of cheaper parts once I explained I was a DIY'er (switch part#SKHCAAB010 and LED part#LED5RGB9).

Had to cut off those stoopid guide pins on each button - no way I'm drilling 2 extra holes per button just so they sit flush!

I burnt out the RED cathode on my demo LED so you only see blue and green here but it gives you an idea of what I'll achieve. The other hint here is that I filed down the LED housing so I could bend the legs 90 degrees and fit the LED in the switch facing upwards to get the brightest effect.

Monday, November 24, 2008

selecting components - faders

Again the only hard rule here is the fader must be 10k linear. I decided I wanted a non-motorized, nice full length 100mm type and they had to be slimline and narrow enough to fit nicely next to the buttons on the custom channel strip modules. I ended up finding a very nice ALPS model which wasn't too expensive and had a nice matching knob that was cheap too, sourced from RS Components (fader part #263-3270 here, knob part #281-7210 here).

Sorry I never took a nice pic of these but you'll see later on when I get to the channel strip modules.

selecting components - pots & knobs

The MIDIBox hardware dictates that your pots must be 10k linear - that's about it. What I've heard is that for this particular application you don't have to get the most expensive high-quality pots. That left a lot of choices, so I decided that I wanted a standard 16mm type with a shorter 6mm D-style stem so I could mount them close together, without having to PCB mount them and without having to trim 128 stems (annoying) and that most D-type push-on knobs would fit. I ended up finding the cheapest and best match via Electus Distribution, who supply JayCar retail outlets, so you get them cheap (part #RP7510 product page found here).

Knobs were a little harder. I won't have a rant about how expensive nice components are but it's obvious the industry manages a tight strangle-hold on profits by keeping nice components expensive - especially in relation to DIY or prototyping. After spending several weeks sifting through lots of options there was really nothing available for my purpose (I even considered making my own out of aluminium or perspex rod). I needed a simple, small diametre (more than 10mm is no fun on the fingers) that suported a color indicator or cap, that would fit a 1/4" D style pot and was less than $1 AUD each. In the end what I discovered was the nice cheap knobs I got as a sample from Electus/Jaycar might work. They fit a 6mm spline pot which was originally no good to me, but I fitted a 1/4" drill to the drill press and easilly drilled a couple out and they then fitted on perfectly - the snug fit ensured they won't come loose or need a grub-screw or need to be glued and are seriously cheap in bulk and come in 5 colors! (part numbers HK7730, HK7731, HK7732, HK7733, HK7734)

Sunday, November 23, 2008

uploading the midibox software

You could write your own operating system and application for the cores from scratch (or modify existing ones provided on midibox site) - the PIC18F is well supported and you can write in both assembly and even C for those apt enough for all that jazz. I decided I would lean on the hard work done by TK and the MIDIBox community and upload MIOS (the operating system) and MB64E application. Both these are mature and have been hand optimized over a long time by very apt and passionate individuals, so a lot of hard work is done for you there (thanks TK!). Basically I followed these steps on the MB WIKI...and it all worked fine the first time for both cores, very impressed!

building modules - lcd

You dont have to have an LCD especially for this kind of project, but I decided I wanted one because you can, and it can look nice once it's running. There are a long list of LCD modules available that are compatible with the Hitachi HD44780 standard so that's a no-brainer. I went for a cheap 2x16 backlit thing from Mike's MIDI Shop (part# Nanox NDM162). The only hard part here is making up the cable that plugs between the LCD module and the CORE. You're a bit on your own here because it will depend on the LCD module you buy as to what the pin outs are, but most of them are pretty standard so you should be right. Download the datasheet for the one you buy and then read this or this and you'll soon have it worked out. I used flat ribbon cable and IDC header connectors which made it pretty easy, just go slow and think it through. I was pretty happy when after a couple of hours work the one I made worked first time...lucky!

building modules - din

The DIN, or Digital In modules are what your buttons connect to and are pretty straight forward. These were a fairly tedious to put together - lots of resistors and IC sockets and a few tricky parts where copper tracks are not very wide. I advise you check for bridged solder joints as you go with these, and invest in a magnifying glass unless you have superman eyesight.

building modules - ain

The AIN, or Analogue In modules are what your pots connect to and basically provide a way of the core to know when a knob has been tweaked. These were fairly quick and easy to knock together.