Using a CASIO PC board as a MIDI controller

A simple question to ask and if this is possible for conversion:

You have a CASIO keyboard where the PC board needs the carbon buttons under the keys to make contact on the PC board. You would like to use that PC board as a controller since it has MIDI out.
How would you attach the wires from a switched keyboard to that PC board since the etched imprint on the PC board looks a bit complicated to figure out what is what.

Thx a bunch - KAR

KAR,

Generally those PCBs are actually a matrix etched into the copper. Each conductive pad provides a 'switch closure' with resistance type of action. The perfect switch has no resistance and mechanical switches have very little so you may need to add some resistor in series with the connection. Some of those patterns have a coating which is very difficult to solder to also. Have you considered a way to use the conductive pads as is? I also occurred to me that putting long unshielded wires on the switches may cause unwanted levels of noise from the matrix scanner. I lean toward a mechanical solution or a metal enclosure.

Tom

Thx Tom for your replies and suggestions. I do feel the same way - staying with the simple switched contacts to eliminate the noise in the closed contact.

It was worth a try - KAR

I'm not so sure noise would be a major issue, especially if you mounted the PCB relatively near the keyboard. say within a foot or so. Lead length would be around 2' max. MIDI is fairly robust and careful wire routing should work.

You could do a test by extending the wiring from several contacts and see what happens. If you are not familiar with matrix switching, it would serve you well to do some homework. Essentially, it's not that complicated. Most circuits use a system of 8 key contacts per 1 common and they are laid out sequentially. In other words, for every 8 keys, there should be 1(separate) common bus. The second group of 8 keys are connected key for key to the first group of 8, but have another (separate) common, and so forth.

A search of such products will show this much clearer. I have some circuits at home. When I get back I can check if you haven't already found one. Don't be confused by the other circuits on the PCB, the bottom line is, when a (keyboard) key is pressed down, a single connection is made. You would just be extending that connection. You can download a free program http://www.midiox.com to verify what is happening with the MIDI messages. There is an equivalent program for MAC's , http://www.snoize.com/MIDIMonitor

This isn't rocket science and definitely has been done by others. Write down everything you do. I sometimes take a photo of a PCB before doing a mod. Another suggestion is to connect the MIDI output from the Casio to your computer and use one of those MIDI programs to see what MIDI messages are being sent (by the Casio). Log those for future reference.

Rgds,
Ed

Kar,
I was actually refering to the electrical noise coming from the scanning of the key matrix which is usually at a much higher frequency (maybe 1 Mhz?) than the MIDI which is about 31 kHz. But like Ed says, it may not be a problem. It should not be a problem in the MIDI circuits.

Can you explain more what you want to accomplish? It might change the answers a bit.

ED,

It is my observation that many if not most of the MIDI keyboards use an octave matrix of 12 X something where something is the number of octave commons to include all the keys. In the case of 61 keys the scan on the 61ES is 12 notes by 6 octave commons I believe. I know my Yamaha keyboards have always used that matrix and I think my Casio and M-Audio do too.

Can you explain more what you want to accomplish?

Thx for all of the replies on this topic from the fellow Hauptwerk members.

Basically, I have an old HAMMOND manual assembly that has the naked switch contacts underneath and wonder, since soldering is elementary for me to do, is to disassemble a small CASIO keyboard and use the PC board which also contains the MIDI controller interface on it, solder 26g wire from the switches to the PC board to take advantage of that controller circuit on that PC board. I've seen a similar project from a site where a fellow Hauptwerk member took a small keyboard apart to use that PC board's MIDI controller for his pedalboard project since he added microswitches to the pedalboard,soldered wires between the two devices and this pedalboard mod worked without a hitch of a problem.

..what I'm shooting after ... thx KAR

Do you have a pedal board?

Rgds,
Ed

Oh yes, I do have a pedalboard that I wouldn't mind to use switches on it as well .... This is a new world of the "Virtual Organ" that I'm getting into and seeing other topics on the "handyman's" way to go to make due in what you got available.

If the pedal board doesn't already have switches, I have in the past used recessed alarm magnets/reed. Usually around $40 (which includes shipping) for 32 to these. Just a thought.

Rgds,
Ed

That sounds rather 'do-able' as they say.

Tom

Hello Kar and Tom

I've used a Yamaha keyboard (with conventional MIDI out) and an Evolution eKeys 37 (USB MIDI output) to midify pedals and pistons. It's a bit fiddly but not difficult. I assume that the Casio system will be very similar.

If you look at the key contact area of the circuit board, you will see that for each group of (probably eight) notes, one side of each contact pair is connected to a common, which goes to another area of the board where there is a contact point for the next component. Similarly, the other contact will go to a track, again leading to another component. The reason for mentioning the "next component" is that this is the easiest place to make your connections. Then all you need to do is to connect the reed/micro switches or contacts in groups of 8 to a common and on to the correct common on the board - easy to solder at the points described above - and each of the other switch terminals to the other contact point.

On my pedal board the cables are up to 60cm, and the piston cables will be rather longer. There are no problems with crosstalk, audio interference etc. The cable used is either similar to or actual alarm cable.

My only other thought would be that it would be easier to use the MIDI keyboards themselves for the manuals, unless your manuals are particularly well made and have a good "feel".

For 2 different pedalboards, I've done what you're asking.

For the second pedalboard, I dismantled a small Fatar midi-controller. It contained 2 circuit boards, one for the midi output and the other, like the one you described in the Casio. Using an xacto knife, I scraped away the carbon pads, revealing the copper. I then drilled holes for the wires, using a very fine drill bit (#60, I think) and a Dremel. This gave me the wiring matrix for the each of the pedal switches. The longest switch wires are several feet long and have had no problems with noise.

Since the Fatar was velocity sensitive, it required 2 reed switches per pedal. The Fatar didn't work properly with just 1 switch. If your Casio is velocity sensitive, be sure to see if you can switch it with just one switch or not.

Pedalboard 1 (many years ago, before Hauptwerk) used a small Casio without velocity sensitive keys. I didn't dismantle that one. Instead, I put a 25 conductor D-shell connector on the back of the keyboard and mirrored the internal bus to it. In this case, I think that I scraped the laquer coating off of some of the copper traces and drilled through the traces. Then, I connected the pedalboard switches to it through a ribbon cable. For switching, I made my own out of bare brass spring wire (bad idea!) But other than having to constantly fiddle with the switch wires, it worked.

I had planned to do the same thing with some old electronic organ keyboards I picked up, but I ended up building an ugly stack of surgically altered M-Audio keyboards instead. (They work so well for my use as a practice instrument, that I have no plans to make them prettier.)

Kirk