lylehaze

Moo: More changes, Assuming that's a Bipolar supply (+ and -) The transformer center tap is GROUND for both regulators. The + side of the bridge (both cathodes together) goes to 7805 input. The - side of the bridge (both Anodes together) goes to the 7905 input. http://www.midibox.org/dokuwiki/lib/exe/detail.php?id=pga%3Abuildregbrd&cache=cache&media=pga:txandbridge.gif CAUTION: the 78xx series are "In, Gnd, Out" pin order. The negative 79xx series ARE DIFFERENT!! Have Fun, LyleHaze

Sorry, I've been away for a while. The good news, I have a job now! It's a 2+ hour drive each way, so I don't get much free time. Multiple capacitors: Why? 2 reasons.. A Big cap and a little cap: Big cap filters the power, little cap is much more effective for high frequency noise. A bunch of big caps: Will fit in a low-profile case better than one cap that is the sum of them all. That's especially useful if you are fitting your toy into a 1U rack mount. Have Fun, LyleHaze

"IMO it is bright 'cause it is 74HC595 DIP and not SOIC." I've never seen a 74 series chip with different ratings for different package styles. But it looks really sweet! Have Fun, LyleHaze

Moo: You are asking all the right questions. I don't have "proper" training, but I'll take a shot at a few answers for you, and if I've got something wrong, I'll hope that a smarter person will correct me. Capacitor values are "magic": It's true. To choose the right capacitors, always choose a voltage rating higher than your expected voltage, and a capacitance higher than you need. This is especially true for electrolytics, as they will lose capacitance over time. How much you need depends on load current, allowable ripple, and supply impedance. I'll get back to current and ripple later. There is math involved in getting it figured out, or just shoot high and test the circuit. :-) Does rectifying AC cause a voltage loss or a voltage gain? Yes. You will "lose" the forward voltage of the diode in the rectifier. This is usually 1 or 2 volts. But your meter will tell you the voltage is higher! To understand this, picture an AC wave. This is a sine wave going up and down in nice smooth waves. the centerline will be ground. half the time, the wave is abnove ground, half the time it is below. Now we will add a diode to "half wave rectify" it. Two things happen: The positive voltages will be about 1.5 volts lower (diode forward voltage drop) and the negative voltages will flatline at ground (reverse biased diodes do not conduct). It is no longer AC, as it has no negative part. It is 0 Volts half the time, and somewhere above zero half the time. With me so far? Now we add a big capacitor to "smooth" this pulsing voltage. What happens now depends on the load we are supplying. If there is no load at all, the cap voltage will rise to the top of the voltage peak, and there will be (almost) no ripple, as there is no load to drag it down. But as we add a load to the supply, the capacitor will discharge during the times between the voltage peaks. This will cause some "ripple" in the voltage readings. The greater the load, the more the voltage will fall between the peaks. Also, a larger capacitor will give less ripple in the voltage. Obviously, any transformer will only reach it's "peak" voltage for a small percentage of time. It spends most of the time swinging back and forth between the peaks. so the voltage rating of the transformer is not the "peak" voltage, but the "Root Mean Square" of that peak. This is a more realistic description of the total power available. That's why converting AC to DC never comes out as easy as you think it would. The results depend on a lot of details that are different for each project. There was a java applet somewhere that draws this all out.. I don't know where it was though. I hope this helped.. LyleHaze

As mentioned above, getting multiple transformer windings does not eliminate the need for regulators. According to the T.I. datasheet for the 78xx positive regulators, you must provide 2 or 2.5 volts higher input voltage than you expect for the output. For a 7805, you must give no less than 7 volts (vout +2) for a 7809, no less than 11.5 volts (vout +2.5) for a 7812, no less than 14.5 volts (vout + 2.5) So the common way is to choose a transformer that will supply the highest positive voltage you need, and let the lower ones burn a little extra heat. We need multiple secondaries, or center-tapped secondaries, if we want a bi-polar supply, with both positive and negative voltages. Doing it with two transformers works fine too. Most transformers with multiple secondaries at different voltages are custom made for a specific product. That's why you don't see many of them at your supplier. It's cheaper than using multiple transformers, as they can all share the same primary. Heatsinks: I often use the metal project case as a heatsink for the positive regulators. I just insert the legs from the back of the board, and don't solder it until the board and regulator are mounted. Positive regulators (78xx) have the tab grounded already, so no problem there. negative regulators are NOT at ground, so either insulators or separate heatsinks are required. You can make your own parts for Eagle too, if you want to make library parts that match your suppliers heatsinks. Adding up all your power needs is important. 100ma per LED? That sounds pretty bright. Mine operate at 5 to 20 ma each. I suppose if they are multiplexed you might be pushing higher currents..?? Have Fun, LyleHaze

I'd like to get a job. I'd like to see MBMixers become a more common project (right now I have the only one) I'd like to finish a non-MB PIC audio project I call "The Whistler" I'd like to design animated lighting for stairways. I'd like to teach then world to sing, in perfect harmony... LyleHaze

"JSx If you intend to stay around here then I suggest you cool it with the attitude." True Stryd is very helpful, but then users like JSx are very important too. Stryd gets hungry sometimes. We need a steady supply of newbies to feed the monster.. :-) Just joking folks.. Smiles all around the thread. ;-) LyleHaze

Based purely on the picture given, I'd say you would need a 7812 and a 7912. But that's just a guess. :-) LyleHaze

very nice. Good idea. Simple, attractive, protective. I have a LOT of "naked" projects that could really use this kind of protection. LyleHaze

You stated: "50 V Limit is no problem for MIDI, I think. MIDI is 5 volts." But the Wikipedia reference stated "50 V and below" Last time I checked, 5 volts is below 50 volts, at least for positive voltages. The failure rate for optocouplers is relatively high, both for complete failure modes and for gradual degradation. Replacing the optocoupler is a good practice for a failed or temperamental MIDI Input. I would change the opto with a new, fresh replacement before trying to re-design the circuit. Have Fun, LyleHaze

Stryd_One said: "community needs to act like the group of intelligent engineers that we are," Hey Stryd, apparently you're new around here. ;-) Come join us in chat and see how long you can continue to support that assertion that we are "intelligent". Just funnin' LyleHaze

Those links are actually to a site that documents the MIDI standard(s). While I have never used Cakewalk, I would be very suprised if it could not synch to an extrnal MIDI clock. What you would need is something like: The Bellows crank turns a low-resolution encoder. A MIDIBox core reads the encoder, possibly scaling it, and transmits MIDI CLOCK events every (n) pulses. The MIDI OUT from that core connects to a MIDI IN for Cakewalk. Cakewalk has the desired MIDI file loaded, and is set to follow an external MIDI clock. CakeWalk drives MIDI OUT To the same (or a separate) Core that controls the DOUT module(s) that drive your organ. At least, if I understand your question.. but maybe I've got it wrong. Have Fun, LyleHaze If you want it "all in one", you will need to write a Format zero MIDI file player (I have a code that will get you started), and you will need some kind of storage for your MIDI file(s). If I were you, I'd start with doing it through cakewalk first, to get that part ironed out before going forward. [edit] matched process to details in the original post.

The tempo of a MIDI file is defined in a Tempo meta-event, as part of the MIDI file format. You can learn all about it here: http://home.roadrunner.com/~jgglatt/tech/midifile/tempo.htm So to "play" with the tempo, there are two approaches: You can add a bunch of tempo change meta-events to your MIDI file. This would work only if you knew in advance what all the changes are.. OR You can Synchronize your sequencer to an external clock, and then all you need to do is to create MIDI clocks by hand as you go. http://home.roadrunner.com/~jgglatt/tech/midispec/clock.htm This would allow "live" playing with the playback rate. Something like this COULD be made with a core and a encoder, using the pulses from the encoder to trigger the clock messages. You would probably also want buttons for start-stop-song position-song select-whatever else. Sounds like fun, LyleHaze

Somehow I get the feeling I'll accomplish nothing with this post. Regarding changing to a Schottky diode at the MIDI receiver circuit: "The most evident limitations of Schottky diodes are the relatively low reverse voltage rating for silicon-metal schottky diodes, 50 V and below, and a relatively high reverse leakage current. The reverse leakage current, increasing with temperature, leads to a thermal instability issue." ref:Wikipedia So it would appear to be a poor choice to replace a diode that is normally reverse-biased, as you described in your above post. As for myself, I operate my equipment within the specifications, and it works reliably. I have no great desire to design outside the standards because it "seems to work better" with questionable equipment or practices. You are welcome to hack your stuff any way you want to, but if you want the rest of us to adopt your changes as the "new standard", you might reach a wider audience by petitioning the MMA directly. I'm sure they will review your suggestions carefully. Have Fun, LyleHaze

A good bootloader (like we have in MIOS) means you don't need a programmer very often. But when you do need one, I like the http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en023805PICKit2. It works with a lot of PIC devices, connects by USB, is small enough to be convenient, supports some Microchip SEEPROMS (I have not tried that), has support built in to MPLab, can be used for debugging, has a command line program for use outside of MPLAB, is USB powered, and it's cheap. Hard to beat. When I was using a parport programmer, I "made up" my own 5 pin header for plugging in the programmer. By pure luck, it matches the first five pins of the 6 pin PICKit2 header, so I can just plug it straight onto any of my existing project boards and I'm ready to go. Last time I plugged it into MPLAB, it detected newer software and updated itself automatically. Cool feature. Of course, the MIOS bootloader is still more convenient, because I don't even unplug my MIDIBox from the rack, I just dump a new program by SysEx. But a programmer is still needed for the first time on a new PIC. Have Fun, LyleHaze

FSR's are usually used in a resistor-divider network to determine pressure on the sensor. this is a static reading that will last as long as the pressure does. Piezo sensors actually generate a voltage pulse when struck. This is a short pulse that must be read very quickly, or "stretched" with a conditioning circuit. This makes multiplexing more of a challenge. That should give you enough search terms to get started. Have Fun, LyleHaze

So far, I have only built a 4 board version. I am using it as a simple line mixer, combining eight stereo pairs. I currently have the software configured for 16 channels, for testing purposes. The board designs have not been released to the public. They will be carried in SmashTV's webshop. He has refined the design a bit, and I will announce them here when they are ready for distribution. If you'd like to build your own version, you can find all the circuit design details in the datasheet for the PGA4311. Available from Texas Instruments. When I designed the set, I never thought anyone would build above a 16 channel set. Comments here indicate that some people may want more. I look forward to seeing how far they can be expanded. Since the hardware inputs are CMOS, I doubt we would need much more than a terminating resistor to get big fan-outs. The software will require re-writes for more than 16 channels, but the driver core should have no trouble with that. Comments regarding expansion limits have been posted in the WIKI, and I'll add more details (including confirmation of expansion sizes achieved) as they become available. Thanks for your interest, when the boards become available, I hope we'll get more people interested. LyleHaze

You can't post that photo. I never signed a release. LyleHaze

Goblinz: Most "modern" keyboards aren't made with separate switches anymore. It's cheaper to mass produce the membrane type like the picture above. Werlin: You CAN buy individual keyswitches and design your own board layout just by using a circuit board design program. You "create" the footprint of a single keyswitch, then lay them out any way you want. "Eagle" is free for smaller boards, but will cost you for bigger ones. There are other programs that are free too, read up on the subject in these forums. Stryder-Man: You are so right. wanting to design a one-of-a-kind membrane keyboard is a huge investment in time and money. I suppose anything is possible, but the odds are swinging hard against the likelihood of success at this point. As far as big projects go. I finished ONE. and that's all, I'm tired now. :-) Have Fun, LyleHaze

Ground Loop Issues? Are they both using the same power supply? Just guessing. :-) LyleHaze

re:making keys. Most modern PC keyboards today have the key making contact with pads on the circuit board. I would guess this is not the easiest thing to re-make on your own. Looking for complete keyswitches at some parts supplier (maybe Digi-Key or Mouser in the USA) will give you the flexibility to layout your own key patterns without having to actually "make" each keyswitch. If the legs on the keyswitch are spaced on a 0.1" matrix, you can even use perfboard to make up your switch panel. You might look at some of the buttons that others around here are using. There was even a few threads about adding your own lighting under the caps of some button types. re:Matrices I have no experience with doing switch matrices in MIOS yet. Have Fun, LyleHaze

Sounds Like you have chosen an ambitious first project. Good for you! I will offer the following thoughts on the subject: You are wandering into at least three different areas all at once. You wish to learn more about MIDI, You wish to learn more about electronics, You need to know something about how PC keyboards work. If you are willing to stick with it, this project can be done, and there are people here who will help you along the way. But you must understand that it will take time, study, and patience if you want to pull it all together. If you expect to be finished with this project in a few days, you will fail. I think a reasonable guess would be a few weeks to a few months, if you stick to it. Your time will be well spent, and at the end, you will have a device of your own design and a great deal of new knowledge. Now, you asked for more information. To learn more about how MIDI works, I like this site: http://home.roadrunner.com/~jgglatt/ Click "Technical Documents and Programming", then "The MIDI Standard" Read all you can, then read it again. It's an incredibly complete site. About electronics, I'm not sure where to send you. It really depends on how much you know already. Lief has it right, build a core, DIN, DOUT, and LCD display. Those can be purchased as kits. Once they are built, study the schematics and if you don't understand something, ask questions. The real "magic" comes when you can see the links between hardware and software, and better understand the big picture. Playing with DIN and DOUT modules will get you much closer to that "Aha!" moment. Finally, you can follow the 64 keyboard project for ideas (I have not looked at that yet), Or you can hack the keyboard keys to a DIN module, either discrete or in a matrix, or if you want a more "standard" keyboard, you might go study the PS2 keyboard protocols, and try programming your own. That would give you the choice of hundreds of inexpensive keyboards to choose from. That kind of information is best found with a tool like Google. Try "PIC PS2 keyboard" Have fun, but understand that it will not happen overnight. LyleHaze

I always liked the Headline at Jeff Glatts site: "MIDI is the language of the Gods" Does sound a bit ominous. Might scare away the newbies. Perhaps some reference to the DIY nature of this group would be useful, since that is the point of a frequently repeated discussion. Or we can help to support the ISP costs by selling perfume! LyleHaze

Looks great from Firefox, but I am usually on my OS4 machine, which doesn't yet have a decent browser. I'll stick with the classic look for now. But hey, it's an option, so everyone gets to choose their own way to go. I really like the "Buy a Beer" option, there's a few people here that I'd really like to show a bit of thanks to. Then again, how about a "throw a beer at" button for some of the other people? :o As far as Thorsten taking all the credit, I am AMAZED at what has been accomplished here. Yes, it's a team effort, community powered and all that, but keeping a community of this size "managed" is not easy at all. He has done very well, and chosen his team well also. But that's enough for now, I'll save my praise until I can afford to buy him a beer. LyleHaze

MBStor is a project based on the Vinculum VMusic2 device. It allows read/write file access to a USB flash drive. This might be good for projects that need more space than you can find on a bankstick. It also can play MP3 and Format 0 MIDI files on it's own internal audio chip. The core drivers are here, written in ASM. It is setup now to take all console I/O from SysEx messages. This can be changed as the user wishes. I have a CON: to SysEx program on my AmigaOne, I will gladly provide the source to anyone who wants to write a OSX/Linux/Windows port. The VMusic2 Home Page: http://www.vinculum.com/prd_vmusic1.html The instruction set we get to play with: http://www.vinculum.com/documents/fwspecs/UM_VinculumFirmware_V205.pdf The MBStor distribution archive is on this page: http://www.midibox.org/dokuwiki/doku.php?id=lylehaze Have Fun, LyleHaze