Hello

I got one e-mail [ [url]http://casainho.net/tiki-view_forum_thread.php?comments_parentId=2&topics_threshold=0&topics_offset=0&topics_sort_mode=commentDate_desc&topics_find=&forumId=1 ] from one guy offering work to the Homemade MIDI turntable Open project.

We would like to make one TODO/wishlist list.

If anyone want to check the project page and give some ideas, we appreciate.

Thank you.

JPCasainho - www.Casainho.net

Great you have a team effort happening! No wishlist items right now but email me to hassle me and keep saying "resonance cascade scenario" -- to remind I have a really good demo example you can use with the turntable.

obiwannabe, Thank you.

Later I will ask you for that demo.

Some questions:

• What protocol should be used to communicate with PC?? MIDI isn't slow? - I plain to use Linux!!

• Should this project be commercial?? I am having problems in getting an turntable to electrify with this electronics hardware - I would pay to someone that made for myself the turntable in wood, plastic or metal. Where can I find such shop?

> What protocol should be used to communicate with PC??
> MIDI isn't slow?

MIDI is not just a protocol, it is an entire communication system from the physical layer right up to the data layer including baud rate and connector specs. MIDI as a protocol could be run much faster over USB2 or ethernet, but a sensible modern extension to MIDI would encapsulate it inside OSC or something like that and send it over a session aware layer. MIDI has had 20 years and now it's probably best to just bypass it and go straight for OSC over ethernet. That would also bypass all those "driver" issues for Windows users too.

> I plain to use Linux!!

An excellent choice if I may say so sir! Perhaps it's time to look at Linux SBCs with built in network and USB. You can get tiny ones that are no bigger than a matchbox and single chip FPGAs that you can write your software into. Check out http://linuxdevices.com/

> I am having problems in getting an turntable to electrify with this
> electronics hardware

You will not drive a turntable motor from USB. The current demands will kill the source. You need an external PSU. 12v at about 1 amp is probably plenty.

> Should this project be commercial?? I would pay to someone that made for myself
> the turntable in wood, plastic or metal. Where can I find such shop?

In your garage. There's no reason not to start a small commercial enterprise making these things but you need to do a bit of defining exactly what the function is, who will buy it and in what parts of the world. My honest advice at this stage is that you don't yet have a saleable product. Needs more development. It's a great project and demonstrates ingenuity in using the optical sensor, but you need to very clearly define the exact function and software it is designed to work with and why. In a funny way you have to think in reverse. Start with the constraints. The target customer is the overall most important consideration. Choose the biggest group like Reaktor users and build it for them. The housing is probably the single most important design factor. Guess how many units you might sell and design around that. A thousand is a reasonable prospect from a website shop, over a year or two. You need to work out the labor costs for manufacture, how long will it take you to build each one? Maybe you can do a deal with a manufacturer to buy and retrofit existing turntables for a first low volume project. Or change the design to be a turntable accessory because many people already have an old turntable in their junk room.

Before getting anything manufactured you need a serious prototype, something you can show to an engineer who can give advice on large scale production. Product design is a lot of odd things you never thought of before, but many are common sense. Heat dissipation, EMI shielding, where to locate certain components for accessibility, physical strength, vibration. If you want to sell a product in most countries it needs to pass some basic safety requirements. Having external power supplies will solve 90% of these in one go. The most expensive ways are injection molded plastic. The best ways in the modern culture are good old fashioned wood and metal, renewable and recycleable materials. Do some cost calculations for folded steel box sections, extruded aluminium and plastic housings. Think about assembly all the time. Contact local engineering companies and get quotes, they are always happy to send single samples for free if you are serious. Use standard components wherever possible. Be creative in reusing things that are already mass produced and adapt them to the design. Think about weight because of shipping costs. Look at your competition all the time too. Think about why people would buy your turntable in preference to one of those DJCD boxes. How will you market it, what are the key features? The good news is that because of the economy in the US there will be a renaissance in small manufacture over the next decade. People have got used to the idea that we just design stuff in the West and let the Indians or Chinese build things. That economic pendulum will swing back and we find there's a shortage of skills in manufacturing. Getting a good base in product design now could pay rewards further down the road. Most first business projects are unsuccessful, don't let it knock you back. The second or third project is the one that pays.

First of all, let me real "thank you" for all your words! I appreciate.

@obiwannabe said:

> What protocol should be used to communicate with PC??
> MIDI isn't slow?

MIDI is not just a protocol, it is an entire communication system from the physical layer right up to the data layer including baud rate and connector specs. MIDI as a protocol could be run much faster over USB2 or ethernet, but a sensible modern extension to MIDI would encapsulate it inside OSC or something like that and send it over a session aware layer. MIDI has had 20 years and now it's probably best to just bypass it and go straight for OSC over ethernet. That would also bypass all those "driver" issues for Windows users too.

Okok, I understand. I will look at OSC

However, I am looking for a cheap and simple way to communicate with Pure Data, without the need to write any special driver for Pure Data and OS.

@obiwannabe said:

> I plain to use Linux!!

An excellent choice if I may say so sir! Perhaps it's time to look at Linux SBCs with built in network and USB. You can get tiny ones that are no bigger than a matchbox and single chip FPGAs that you can write your software into. Check out http://linuxdevices.com/

Eheh - I plain to use Linux on PC, with Pure Data, so the communications protocol should at least work very well on Linux.

About hardware, I am already using a microcontroler(not an FPGA, I have no knowledge for that but I would like) with C programing but with a RTOS, Real Time Operation System, in this case, the FreeRTOS, with a license alike GPL

I must say that for now, this microcontroler with C and with FreeRTOS is more than enough

@obiwannabe said:

> I am having problems in getting an turntable to electrify with this
> electronics hardware

You will not drive a turntable motor from USB. The current demands will kill the source. You need an external PSU. 12v at about 1 amp is probably plenty.

No, I didn't explained myself well

The problem is to get a cheap turn table!! For cheap and simple project, It will not have any motor... Its more just a circle that we can turn right or left, more quick or not...

@obiwannabe said:

> Should this project be commercial?? I would pay to someone that made for myself
> the turntable in wood, plastic or metal. Where can I find such shop?

In your garage. ...demonstrates ingenuity in using the optical sensor, but you need to very clearly define the exact function and software it is designed to work with and why.
... Choose the biggest group like Reaktor users and build it for them.

I want to build especially this project for Pure Data, because Pure Data is Free Software and I think is great, fair and the way I think.

I would like that this project grow with Pure Data community help, for Pure Data people, so, I would like that It be simple and cheap.

The optical sensor was chosen because is really cheap, easy find on local shops and have good detection of movement.

I just talked about commercial project, because It would be simple, more accessible to Pure Data community If anyone could buy already assembled or at least the parts to assembly.

What I have difficult now is to get an kind of turntable in wood, just a simple base in wood with a circle that turns left and right...

Thank you for your wisdow

Heyy mate!

@casainho said:

However, I am looking for a cheap and simple way to communicate with Pure Data, without the need to write any special driver for Pure Data and OS.

That would be the nice thing about ethernet, and why I though of these really cheap COM (computer on module) things that are about now. Maybe it seems overkill but now these things are really commodity items it may turn out cheaper to use a thumbstick sized SBC than to make your own PCB with a microcontroller. Just an idea, I haven't done a serous comparison.

@casainho said:

About hardware, I am already using a microcontroler(not an FPGA, I have no knowledge for that but I would like) with C programing but with a RTOS, Real Time Operation System, in this case, the FreeRTOS, with a license alike GPL

Ah yes! I've seen these too. Never played with one though. I used to use PICs but found them just too slow and limited to anything much with. How much are they per chip? And if you make the PCB, roughly how much does the total cost of the board and uC come to?

@casainho said:

I must say that for now, this microcontroler with C and with FreeRTOS is more than enough

Okay, yeah I misunderstood - sorry, I wasn't concentrating - I was thinking you were going to make something that needed to run Pd on the board and then send out your signals from that.

@casainho said:

The problem is to get a cheap turn table!! For cheap and simple project, It will not have any motor... Its more just a circle that we can turn right or left, more quick or not...

I keep thinking about this and it's difficult - like how the hell do they manufacture turntables? Ones I've seen look like die cast aluminium, and it's not relly a garage industry technology. Cutting a perfect circle 12 inches diameter isn't easy for any material. I think it has to come down to what I said - finding an existing mass produced item you can subvert. After the platter the next hardest part is the bearing.

I had an idea for that... just use an electric motor, most have holes for mounting tapped into the front already and you get two really good bearings (one in each dime) for the price of one. Plus you can pick up motors for almost no money. Just because you're not going to use the motor to drive it - you can stil use one

@casainho said:

I would like that this project grow with Pure Data community help, for Pure Data people, so, I would like that It be simple and cheap.

People who will test this and give you cool feedback are DJs, whether they are Pd users or whatever. The reason I suggest Reaktor is nothing to do with that software really (although it is a good choice because Reaktor has OSC) but because there are lots of people who use it who are
probably also DJs while Pd has a few, probably less because it is more cerebral (no offence meant to any DJs).

@casainho said:

The optical sensor was chosen because is really cheap, easy find on local shops and have good detection of movement.

That's a really good design I think, not just cos it's cheap but because it's clever - robust, reliable, no physical or electrical contact!

@casainho said:

I just talked about commercial project, because It would be simple, more accessible to Pure Data community If anyone could buy already assembled or at least the parts to assembly.

Sure, but if you're going to make more than 100 of anything you should look on it as a business I think, not hugely profitable but consider the time you put into making this. You don't have to limit to Pd - it's a general purpose controller once you manufacture it. He he - I did get carried away thinking of you starting a little factory for these and one day being able to go to my music store and order one and say I know the bloke who designed this I want to see lots more success stories like Reatable with people developing with Pd and manufacturing products.
I spoke with some guys at O'Reilly a long while back and they were enthusiastc about Pd for the magazine called Make, but since then I haven't seen any ideas they took up to publish deigns with home designed hardware and Pd. Maybe you should get in contact with them - Steve Weiss was the guy I spoke with, dunno if he's still there. Building and selling hardware seems one of the most attractive and fair ways of using FOSS in a profitable business. Because you're actually selling something that you designed and manufactured yourself. Well, I think whatever scale you make this on it will be desirable and you will sell a few. I'd buy one off you!

@casainho said:

What I have difficult now is to get an kind of turntable in wood, just a simple base in wood with a circle that turns left and right...

Here's a brain fart....! What is already the perfect size and very very cheap to buy lots of? A 12" vinyl LP... Maybe glue a couple together to get more weight. You need ones that aren't warped. Older ones, 1970-1980 are better quality - thicker. Somehow you have to adapt a spindle to fit the center perfectly.

Question: How are you going to mount the optical sensor? Will it read from the edge of the platter or will it shine down on the surface?

Hmm, exciting stuff. Have fun with your experiments.

a.

How much are they per chip? And if you make the PCB, roughly how much does the total cost of the board and uC come to?

Microcontroler ATMEGA8 ~6 euros. The circuit is very very simple, so, PCB should be very cheap!! Here is an image of the circuit: http://casainho.net/show_image.php?id=77

Board + uC, maybe about 15 euros. But, there is the need of MIDI<->USB converter, more about 30 euros. So, no more than 50 euros the electronics of the project.

I had an idea for that... just use an electric motor, most have holes for mounting tapped into the front already and you get two really good bearings (one in each dime) for the price of one. Plus you can pick up motors for almost no money. Just because you're not going to use the motor to drive it - you can stil use one

Good!! I will start to looking at motors repair shops in my city, maybe I can find bearings, shaft and metal plate already mounted

People who will test this and give you cool feedback are DJs, whether they are Pd users or whatever. The reason I suggest Reaktor is nothing to do with that software really (although it is a good choice because Reaktor has OSC) but because there are lots of people who use it who are
probably also DJs while Pd has a few, probably less because it is more cerebral (no offence meant to any DJs).

I don't have any DJ friend in my city and I am not a DJ... It's a difficult to find someone and get good feed-back.

How about to create a good solution for DJing, with PD and with this hardware? - A patch for PD and this hardware? - maybe more DJs would approximate from PD...

A question, can you please tell me in what ways can I communicate with PD? MIDI, netsend?? - OSC is not build in PD default installation, right? - I would prefer something that is already on PD...

About Makezine, I think I will wait sometime, get something more robust and contact them to publicity the project.

@casainho said:

The optical sensor was chosen because is really cheap, easy find on local shops and have good detection of movement.

That's a really good design I think, not just cos it's cheap but because it's clever - robust, reliable, no physical or electrical contact!

Question: How are you going to mount the optical sensor? Will it read from the edge of the platter or will it shine down on the surface?

Ok, the optical sensor is really nice because of that you said, however, there is one dificult, as you may know, the mouse must be really near from the mousepad or the surface... so, the mouse must be really near from the plate!!

Putting mouse on the surface, I think It's not good because applying force to the plate when turn it to rotate, may change the distance from plate-to-mouse.

The distance from edge of plate and mouse should not change very much when applying force to plate. Also in the edge we get the highest resolution measure of the mouse, of the optical encoder - I think that there is more resolution than needed

@casainho said:

Board + uC, maybe about 15 euros. But, there is the need of MIDI<->USB converter, more about 30 euros. So, no more than 50 euros the electronics of the project.

Okay- need to get that cost down. The MIDI-USB is the weak link. You're converting down to the slowest obsolete signal and then back up to a fast one

Perhaps the way to go is old RS232 serial. Reprogram the UART to a higher baud rate like 9600 so you can use it directly to a D-connector.

Vanilla Pd has basic serial objects built in afaik

@casainho said:

Putting mouse on the surface, I think It's not good because applying force to the plate when turn it to rotate, may change the distance from plate-to-mouse.

The distance from edge of plate and mouse should not change very much when applying force to plate. Also in the edge we get the highest resolution measure of the mouse, of the optical encoder - I think that there is more resolution than needed

Agree that it should face the edge of the platter. There is a potential problem - the platter may rotate *too fast* and cause an effect like aliasing that makes the optical sensor think it's moving backwards. Experiments is the only way to find out.