Wednesday, May 27, 2009

Squirrels under the bridge

Yesterday, when I was walking back from class with a professor of mine, we happened upon a group of baby squirrels living in an alcove underneath the concrete where the sidewalk meets the bridge abutment. I was quite shocked to find that they had decided to nest so close to such an active street. There were perhaps 8 or 10 of them out yesterday. However, today, when I came back with my camera, I only spotted four.

Cannon EOS 450D/Rebel XSi woes.

Lately, I have been fussing with the camera, trying to control the shutter release mechanism remotely via my MacBook Pro. Ideally, it would have been nice to use a single library/front-end utility to control the shutter as well as download images from the camera. But I have run into some problems...

It seems that gphoto2 has problems taking control of the camera. I get the following error:

*** Error ***
An error occurred in the io-library ('Could not claim the USB device'): Could not claim interface 0 (m). Make sure no other program or kernel module (such as sdc2xx, stv680, spca50x) is using the device and you have read/write access to the device.

*** Error (-53: 'Could not claim the USB device') ***

Rather than spending my time troubleshooting this problem (gphoto2 support documentation for the mac is virtually non-existent), I brought up my Ubuntu virtual machine and installed the latest and greatest version (2.4.6) of libgphoto2/gphoto2 from the debian unstable repository. gphoto2 (2.4.5) under Ubuntu worked like a charm; I was able to grab a summary of the Camera status, and and configure it. Unfortunately, it seems that libgphoto2, does not support many of the remotely configurable features of this camera. The only parameters I was able to change were the focus lock and storage location of remotely captured images (device RAM/SD). These limitations, however, do not really affect me because all I really need to with the camera is remotely capture images and then grab them from the cam.

Also of note: Although the gphoto2 libraries for the 450D/Rebel XSi claim that you can remotely capture images to device RAM and SD, this functionality doesnt seem to actually work. The only way that I was able to capture images remotely was by using the --capture-image-and-download command line flag.

Because of the difficulty associated with getting gphoto2 up and running with this particular camera, accompanied by the fact that none of the camera options are configurable remotely by gphoto2, I am inclined to create a serial controller for the entire scanner setup. This serial controller would not only interface to the camera's 3/32" tether port, but would also provide an interface to the VXM stepper motor controller that would allow for the operation of the rig without an attached computer. Also, the controller would likely be able to do shutter control across the entire line of Canon SLR cameras.

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Tuesday, May 26, 2009

Microscope Rig

For those of you who don't know, I am working on an automated microscope rig for capturing images of tree ring core samples. The rig, once fully assembled, should consist of nothing more than an optical breadboard with a linear axis and a microscope positioned above.

The linear axis is a Velmex Xslide, and has a leadscrew pitch of 1mm. The attached Vexta PK245 (NEMA 17) stepper motor is driven by a Velmex VXM-1 stepper motor controller. This stepper motor controller is on the pricy side, but has the capability of storing 4 programs at a time. Ideally, it would be nice if the whole rig had the capability of operating independently of a connected computer.

The microscope being used with this project is an old Wild M5, with an added SLR camera adapter purchased from Matrin Microscope. The camera used is a Canon EOS Digital Rebel XSi (450D), which is a fairly new model (The big question: is there third party software to control the shutter?).

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