Ribbon controller update

[Doug Tymofichuk]

Greetings, all!

After many hours of hard work, I have finally produced a 
working ribbon controller. Here are the details:

I started with a 2 foot long piece of 1 1/2 inch diameter 
wooden dowel. This was mounted horizontally on the top of 
an old lamp stand with some angle brackets and wood screws. 
Along the top of this dowel a length of 1/2 inch mylar 
adhesive tape has been applied. Then graphite powder (the 
type for lock and key lubrication) was rubbed into the 
mylar tape until the total resistance from end to end was 
about 100K ohms. Next, I found an old belt that was still 
in quite good condition (too small and not my color ;) and 
cut it to the same length as the dowel. Then I cemented a 
1/2 inch wide strip of brass shimstock down the middle of 
one side of the belt. The belt was then attached to the top 
of the dowel at either end with washers underneath, so that 
it was suspended over top of the mylar/graphite tape with 
the brass strip facing down. Connections were made to both 
parts, and testing began.

Initially I had problems with false triggering, 
particularly when using drum sticks. I discovered that when 
the belt was being struck, it would vibrate somewhat akin 
to a guitar string, so that points on the ribbon that were 
not struck would make contact at times. Tightening the 
tension on the belt was considered, but would make the 
controller less sensitive, particularly at each end, which 
I wanted to avoid. So I eventually applied a strip of 1/4 
inch wide weatherstripping foam to the belt on either side 
of the brass strip, so that the foam is the first thing to 
make contact. This completely eliminated the false 
triggering, without noticeably effecting the sensitivity. 
The controller now functions quite effectively, whether I 
am using bare hands or sticks.

I built a simple sample and hold for the controller using a 
FET and a few op amps. The circuit that I started with was 
similar to that which Eric Barbour uses for his keyboard 
controllers, with a few mods. I installed the electronics 
in a nifty little plastic box and attached to the stand just
under the ribbon controller. It has three controls; pitch, 
which offsets the CV output; width, which increases or 
decreases the CV output range; and glide, which is just a 
simple portamento type thingy. There is one LED for power 
and another to indicate triggering (bright flash) and key 
down (dimmer steady light). As the whole thing is just 
running on a single 15 volt supply, CV output range is from 
about 1 to 14 volts, which works well with my tube 
oscillators but which would also work well with any solid 
state oscillators that I connect it to.

Over all I am quite happy with how this turned out, 
although time will tell how it stands up to repeated heavy 
use.
----------------------
Doug Tymofichuk
dougt at cancerboard.ab.ca