The
camera project grew out of a
slightly simpler idea Jon Grove and
myself had to add a 12+ bit analogue
to digital converter (ADC) to a
modified security came
ra and use a
small microcontroller and USB link
to interface with a PC. From memory
it took several months to choose
suitable components and get to the
stage of a working prototype. This
used the microcontroller to control
the exposure and the ADC to
digitised the video signal a pixel
at a time. An early picture was
posted to QCUIAG to announce the
project and I believed development
work was nearly finished. Then Jon
suggested that as we had a working
‘back end’ we could go the whole hog
and make a CCD camera from scratch.
It didn’t sound like much work at
the time!
Although some parts of the camera
development might appear hap hazard
we have been an surprisingly
consistent with our aims for the
project. Perhaps the most important
is the desire to share our interest
in CCD cameras and electronics. The
first book I read on CCD imaging was
the CCD camera cookbook. This
gives
complete instruction on making a
cooled astro CCD camera. The design
is a little dated now but the
principle of being able to build and
learn at the same time is still very
powerful.
It’s very much this practical
learning aspect that I hope that
other builders will enjoy. Then its
all the more rewarding to image the
sky with a camera that we have both
built and understand.
Throughout the project we have aimed
to use current, tried and tested
hardware rather that the latest
bleeding edge approaches. This
playing it safe has probably
prevented us getting bogged down in
‘novel’ problems and also allowed us
to use more cost effective
components. These choices are
particularly evident in the choice
of readout speed of the camera’s CCD.
Its fast compared with the old
parallel port cameras but relatively
slow when compared to USB2 offerings
from SX and SBIG. However by not
chasing readout speed as a main goal
it has allowed us more leeway with
the components optimised to image
quality.
Where
possible we have tried to be
innovative. As our experience
is with software rather than the
hardware we have where possible
moved the cameras functionality into
the digital domain. Its here where
we can start to innovate a bit. So
the hardware side of the camera has
ended up about as simple and minimal
as we could make it. In so doing we
have ended up with a remarkably
flexible platform on which to build
these cameras. Functions such was
the multi CCD compatibility, multi
readout modes, and expansion
potential stem from having a simple
hardware design.
The camera is never finished. With
many electronics projects once the
last solder joint has cooled that’s
about it. For this camera we would
like to see the completion of the
basic kit as just the start! The
camera has a dedicated expansion
port and the firmware is included to
communicate with other devices over
this link. There are many possible
enhancements both software and
hardware that could be developed
Steve Chambers
