Beginner MIDI project

[tbeck]

I'm using my lockdown time to try to learn a little about electronics. I'm a total novice.

My first goal is to create a simple footswitch to send a MIDI message to control my VPO's combination sequencer. I'm currently using a single MIDI keyboard because my 2M & P console is on the fritz. I'm using a spare key at the top of the keyboard to send a message to activate the "Next" button on the sequencer but this isn't really satisfactory due to having to my my hand so far away while I'm playing.

I'm using an Arduino Uno knockoff (Elego) to learn the basics. I've learned how to create a circuit and code to manage a momentary switch. I also see that there is a MIDI code library so my first goal looks like it might be relatively simple to achieve. However, I don't have a footswitch. Actually, I do have one that came with a digital piano but I can't find it. Also that switch had a 1/4" rca connector and I'm not sure if I could use it. In the meantime my idea is to make do with the ultrasonic sensor positioned on the floor. I'm thinking that if I pivot my foot I can activate the sensor and send a MIDI message. There are a lot of obvious drawbacks to this but it's better than nothing. Maybe.

As for my console, it would be nice just to get it working again. It is a Rodgers 830. After discussing the problem with some of the members here, it seems there might be a problem with the power supply. Perhaps it will be easy to remedy. I can't find any technicians where I live so I'll have to do it myself. It is currently MI DIfied, but it only sends note on/off messages, and CCs for two of the three expression pedals. None of the other controls sends messages. The sound production system doesn't work at all, and I have no interest in using it. So the ultimate solution would be to gut the console and reuse the current MIDI wiring with a new encoder.

I'm going to have a lot of questions as I go along with these projects and I hope I can find some help here.

So here is my first absolute new beginner question. I need to buy a multimeter. Is any cheap one as good as another? Are there any non-standard features that would be helpful when working with organs or MIDI applications?

Thanks in advance for any help or suggestions,

Tom

[jbird604]

Tom,

Best wishes for your new endeavor. You'll be an expert before you know it! It's a real shame that the Rodgers console quit working, but to be honest, we have thrown up our hands and put two or three of those 80's serial-keyed Rodgers organs into the dumpster in recent years. When they are working, they work great, but once they go off the rails, I don't have much luck finding the root of the trouble.

Could be something obscure in the power supply. Some socketed connection that's gone flaky, some little pico fuse that doesn't look like a fuse at all, and then there are all kinds of possible malfunctions in the CPU system. My feeling is that it's hardly worth the trouble if you can't fix it in an hour or two. Just get an old MOS Allen for free somewhere and you'll have a suitable base to build on. That's how I wound up with a sad-sounding Allen MOS in my house -- it was free and otherwise useless, so I have nothing to lose in turning it into a VPO.

As to your question about a multi-meter.. The cheap ones for $15 at Lowe's will do the basic stuff just fine. Measure DC and AC voltages, check continuity and resistance, tell you if a diode is good or bad. These are the most frequent uses I have for a meter. But my REAL meter cost a lot more money than that. I've had it for 20 years or more, so I don't even know what it cost, maybe a couple hundred dollars back then. It does all that simple stuff, but it also does auto-ranging. In other words, I don't need to even guess what the voltage is at a certain point, just touch it with the probes. Doesn't matter if it's millivolts or hundreds of volts, the meter finds it instantly. Same with resistance, and it even measures capacitance over a limited range (though I have a true capacitance only meter that covers a far wider range). So you get what you pay for. I wouldn't spend $200 just to do simple projects, but if you use it every day and need it work quickly and reliably every time, you may need a mid-grade model or better.

Please post about all your experiences with this. I'm really interested in seeing how this goes, as I may be doing some of the same things in the near future.

[tbeck]

John, I would love to get an old MOS for free, but there really aren't any here in PR. I did track an ADC-222 down more or less by accident. I was driving by a Lutheran church and noticed a side door was open. Out of curiosity I went in and the first thing I was was an organ console with a bunch of boxes on top of it! I found the (rector, priest, preacher, not sure of the correct terminology) and asked him if it was available. Apparently it hadn't been used in years, the musicians having switched over to a keyboard. I made him an offer of a couple hundred dollars for it and he said he would gladly sell it but he had to run it by the church council (or whatever).

Apparently when it was bought there had been a campaign to raise funds and family were allowed to pay for a key, or more than one key. So I guess there are still people in the church who donated and don't want to get rid of it even though it is collecting dust in a hallway.

In any case, I have enough trouble with an AGO pedalboard. I don't think I'd be happy with the princess pedalboard. I checked with the nearest Allen and Rodgers dealer in Florida, but there are only a couple of installations here.

Even if I could find a free Allen in the US, shipping is very expensive. It cost me nearly $1000 to get the Rodgers here.

My ideal solution would be to take the keyboards and maybe the stop jambs and the pedalboard of course and find a woodworker or cabinet maker to build a table or something for it. Something minimal. Then, with luck I could figure out how to MIDIfy it myself. I was wondering if it would be possible to reuse the board running from the pedals to the bottom of the keydesk. I'm not sure what the name of that piece is, but it holds the expression pedals and already has the magnets and I assume the reed switches for the pedals. It might make it easier to get the pedals going. It's probably all a pipe dream (pun intended) anyway. But gives me something to aspire to as we slog through this crisis.

[John Kinkennon]

For the multimeter I would look for a manual, not autoranging, model and see no need to go over $30 for basic electronics use. I just saw a Klein tools model at Home Depot for $30 and while there many choices I tend to think that the name brand ensures that the multimeter is not junk and they do provide a good protective cover. It's my opinion that the auto-ranging models are slower to use and I am frequently setting my auto model to the manual mode.

[lizny]

About your Arduino - one of the things I learned along the way is you want a model that does USB MIDI natively, not over Serial USB. the magic keyword you are looking for is ATmega 32U4

[tbeck]

I've just discovered that the hard way. I finally decided that I had enough knowledge of the Arduino to set up my test for the simple MIDI controller. As I compiled my first test program, I was informed by the compiler that I didn't have the right microcontroller to run USB over MIDI.

It looks like there is a way to flash the firmware to make it work, but it looks fraught with danger. I saw some issues on the forums where people had bricked there controllers. So I just ordered a new one with the ATmega32U4.

[Admin]

I've flashed R3 Arduinos to do USB over MIDI. It's not easy, and not all R3 Arduinos have a USB chip that permits this. Best use an Arduino, or better yet a Teensy, that supports USB HID

[tbeck]

I'll order a manual range model. As long as I'm buying, what are some other basic tools I should have. I really don't have anything. Well, a hammer and some screwdrivers, but I'm sure those won't be appropriate. Well, I'll keep the available in case I lose my patience. I don't have a soldering iron or solder. Any recommendations?

[jbird604]

Haha! You might need a good "finishing hammer" if the project gets just too frustrating -- a good old guy I used to work with on a construction crew used that term to refer to a sledge hammer!

[twnelson]

Should diagnosing/repairing the 830's original electronics be unsuccessful, the conversion to using other MIDI encoders is straightforward because Rodgers uses a single bus, non-matrix contact input scheme for each keyboard and the pedals with gold contact surfaces that work successfully with 5V. The stop controls (either tab or DK) are set up similarly and simple to modify. The expression and crescendo pedal pots are already set up to feed ADC inputs.

Been there, done that on dead and non-MIDI consoles.

--- Tom

[physicsmajor]

Careful converting the 32U4 chip into a USB MIDI device before you're REALLY SURE you are done with the project - or have an AVR ISP programmer with access to the ICSP header to reprogram the chip. The 32U4 controls all serial and USB communication with the Arduino, and also houses the Arduino bootloader. Changing that chip to a USB MIDI emulator works, but means you lose the ability to reprogram the main Arduino chip itself (unless you want to access its ICSP header directly).

Basically, work with MIDI over serial USB for as long as possible with a software bridge like Hairless. Then after you think you're done, keep using it that way for a few months. If you really haven't had any desire to change anything, then maybe burn the 32U4 to turn it into a USB MIDI device.

If you do go down the road of converting this to MIDI, OrganDuino may be of benefit. The sketches might be useful to look over even if you don't use the rest of the project. https://github.com/JDWarner/organduino

[tbeck]

Thanks. I've already decided not to try flashing the firmware on the chip. Too risky for a novice. I've ordered an Arduino Leonardo. The organduino is a great resource and possibly the most straightforward way for me to go.

My console has lighted drawknobs and so that might add another level of complexity. I don't really care about them anyway, as I'll be using a monitor. I would however like to get some pistons and at least a couple of the toe studs working, along with expression pedals.

If I only have 2 manuals and a pedalboard, do I still need the Mega?

[tbeck]

I've ordered an Arduino Leonardo which will support USB MIDI. I don't want to risk the Uno and flashing the firmware is way going deeper than I care to. I also don't think the internals of that Rodgers are worth investing any more time into either. So do any of those components have any value to anyone? Should I just haul all of the boards and the amp and power supply to the dump? Are the drawknob jams at all useful to anyone? I also assume that if I'm going to gut the thing then I don't really have to be careful with anything other than the keyboards and the pedals and the wires that are connected to them?

[physicsmajor]

The Leonardo does not have enough pins to simultaneously poll an entire organ manual which is buss-wired. There are schemes which use more complex key matrices to poll a lot of keys with fewer pins, but OrganDuino is designed with each manual being its own row in the matrix. The code around MIDI events and polling keys will work, and you can prototype with the Leonardo. But if you get serious about converting the whole organ, and the organ is buss wired, there is really no substitute for the Mega 2560. Nothing else comes close to its sheer number of pins.

[lizny]

You can get sufficient pins by adding external chips, either port expanders like the mcp23017, or shift registers, like SN74HC595. I used the port expander but realized now that they only do digital input, not analog, which means I can't read the velocity information off my Hall sensors, only on/off.

[jbird604]

I don't want anything out of it, but there is a market for the drawknobs. Those things cost quite a lot of money from the suppliers, and people who are assembling a VPO and want to have lighted drawknobs may pay you well for them. I wouldn't be surprised if they cost $100 apiece if you had to buy new ones today. You might sell each tower with knobs for three or four hundred dollars, if the right buyer comes along. Or offer them on ebay for $20 per knob, maybe. I don't know if other people are selling them, you'd have to watch for prices.

Other than the keys and pedals, which your're keeping, and the knobs, there isn't much of value inside a Rodgers analog of that era. If you knew that the CPU was working, it might have some value, as they are hard to get any more, for folks who are keeping an organ like that going.

The rest of the boards, keyers, output pre-amp, oscillators, and such -- they are so specific to the model they don't have much value as parts. And if someone is keeping an old Rodgers going, they are much better off to replace individual diodes and chips and such than to transplant a complete keyer board. And that power supply and amp, IMHO, were the bane of that model series. So many issues have sprung from the lousy design of those two parts, I don't think there is any need to try to salvage them.

[tbeck]

John, it looks like I might have to break out the finishing hammer.

[jbird604]

It would be a good time to get it out for some exercise!

[twnelson]

Syndyne doesn't make the lighted DKs any more that Rodgers used for years, but Matt sells NOS ones from their stock for $30. Used ones typically show up at around $15-20 individually on *bay.

--- Tom

[tbeck]

Thanks for the info on the drawknobs. Maybe I'll keep them around for a while and see how the project goes.

[tbeck]

I'm going to order the multi meter. I might as well get a wire cutter/stripper as well. What size will I need both for the Arduino project and gutting the Rodgers?

[myorgan]

When you close the handle, the cutters don't meet, or when you close the handle, the strippers don't get close enough to strip. Personally, I prefer a stiff action in the handle so they stay closed while stripping wires.

Not all tools are created the same.:-(

Michael

[tbeck]

And yet it hasn't found its way to the trash bin.

[myorgan]

It still crimps well when I'm doing multiple speaker cords.;-)

Michael

[tbeck]

I'm trying to figure out how to connect my console keyboards and pedals to a MIDI encoder. I've got a couple of pictures here. Although from what I understand the Rodgers 830 has analogue sound, it is digitally controlled.

Here is a picture of the keyboard wiring:

Keys to pcb


The buss


This is the pcb



I did some research on that chip and it is a Schmitt trigger. Apparently it is "...used in signal conditioning applications to remove noise from signals used in digital circuits, particularly mechanical contact bounce in switches."
The ribbon connector is connected to a board which looks like it handles the thumb pistons. The connection then leads to what I am assuming is the CPU. It is a metal "cage" attached to the top left of the first swinging frame at the back inside of the console.

I'm wondering if it is possible to use the output from that circuit as input to a MIDI encoder?

Or am I all wrong about my assumptions?

[jbird604]

Most likely you'll wind up ditching all the Rodgers circuitry and simply connecting your MIDI encoder directly to the key contacts. Most encoders today can be configured to wire directly to the contacts rather than to a matrix of some kind. The Rodgers key contacts are probably arranged on a common buss, which is also the way most encoders want to be wired.

Maybe somebody on the forum has converted a Rodgers analog to MIDI and can give you detailed instructions. I only remember adding a MIDI encoder to a 770 one time, and it seems like we just wired the ribbon cables directly to the ends of the wire whiskers and used the +12 volts that each whisker picks up from the buss rod when the key is pressed down.

[tbeck]

John, that would be nice. There definitely is a common buss but it looks like all the keys are soldered to the circuit board. In my ignorance I'm probably missing something.