Arthur Nichols wrote:

> Further to Julie's comments,
>
> I am a little confused about this thread, having seen the SD card to
> midi adapter on Ebay I was interested from the point of view that
> Floppy Disk players are no longer fitted to new computers, these
> disks are an old technology and I have had many disks that for some
> reason will no longer play.
> I would like something small that could be used on the two Street
> Organs that I have built and fitted with my own design solenoid
> manifolds.

The SD system advertised on Ebay should work without much issue to drive
a small 21 or 31 note organ using Spencer's evalve blocks and MIDI
multiplexing controller.

To drive a small pneumatic organ, there are several electronic circuits
needed.
First there is the valve manifold, which is controlled by a solenoid.
The solenoid in turn is driven by a driver board which contains the
components used to switch the power to the solenoid.
The driver board is controlled by a MIDI converter. This is usually
done by multiplexing a signal after the fashion of a telephone exchange.
Sometimes the driver board and the MIDI converter are combined on the
same electronics board. In Spencer's evalves system the boards are
separate electronics. Typically such a board has a 5 Pin MIDI Din
connector on one end, and screw terminal connectors for the solenoids on
the other.
The remaining electronics are either a small sequencer controller such
as the one on ebay under discussion. This could also be a laptop
computer or a box such as the one sold by Viscount, Yamaha and others.

Alan Pell and others in the small portable organ venue, have been
controlling the smaller organs for years using 30 year old ROM chips.
With a small organ, there is not always a need to use MIDI to sequence
the notes. In these cased the system can be integrated into a single
device which can play a number of songs.

I was contacted by the creators of the SD card system over the weekend
as they were also confused by the intentions of my review of media card
players. My interest is more on the research and development side,
than on the marketing side for such devices. I have not heard back from
them as to what they mean by 255 tracks? I think they were a bit
taken aback, by my cost estimates of what I can produce here in the
Silicon Valley. They were quick to point out that their product is RoHS
compliant which extends to the plastics used in the case. I stand by
the cost estimates I gave, at least for US domestic products that do not
require RoHS. For the UK, they are a better and quicker option.

My review was more to the point, that having made a number of floppy
players, most what remain unsold, I went on to make a flashcard based
players. The results have been, that selecting songs was the weak point
and given the system I have here I find I prefer Van Bascoes player for
use with my band organ, that requires mains power.

This does not mean I have given up on flashcard based players. I am
intending to make a small demo instrument, which is a 20 or 30 note
scale, that I can place into the back seat of my car and take around
with me. Moving even a small organ such as a Caliola gets tricky as it
is about 400LBS. The rental companies still expect one to use manpower
to lift such things onto trailers or the bed of a truck.

As for floppy based players. One of the downsides of floppy disks was
that they are easy to erase when left around magnets or magnetic
materials. They are also prone to dirt clogging the head of the
reader. This did spawn a small industry to supply cleaning disks and
pads which do more to spin the dirt deeper into the head. The heads can
also become mis tracked, which means that a drive will only read disks
formatted on the same drive. I also put a bit of time, and what little
money I had after the dot com bust into developing a new generation
floppy based file player. What is interesting is in the 6 years since I
first had the idea for this, how far hardware costs have dropped.

The chips I use are made by a company called ATMEL. They are used in
programmable thermostats and automotive ignition systems. The company
gives away at tradeshows and sells online a demonstration board for 20
bucks. The demo board has 512 bytes of flash storage, which is about
the same as a single sided floppy disk. The playback code I developed
over these same six years could be ported to this 20 dollar demo board
and the card would contain about an hours worth of music. A popular add
on to the demo board is none other than a SD card for debugging, this is
about 6 bucks. It also helps that code to read SD cards is a popular
homework assignment for college students so there are a lot of examples
of how make simple MP3 players online.

The problem is that no one wants to pay for the time it takes to debug
programs. It took me six months to code the playback software. A week
to write it and the rest of the time to debug it. At rate this would
have been about $50KUSD if I was paying myself the same as I got working
for Apple. In order to recoup this expense, I would have to sell 5000
systems. At best I have distributed a dozen of these boards using the
older more expensive hardware. The main reason I continue to develop
the players and drivers, is so when I go to interviews I can point out
that my skills remain current and I am using the latest chips. In the
meantime, I get to restore and build organs, either for myself or for
others.

That said, I am probably adding more to the confusion. I think the
short of it is if you want something now, get the box off ebay, You
will however need a MIDI to solenoid multiplexer to plug the box into.
For that I recommend Spencer's evalve system.

-julie