Archive for March, 2010
I’ve been looking into creating an automated herbarium of some sort for a while, and I came across the brilliant post about creating some DIY soil moisture sensors using nails and plaster of paris. cheapvegetablegardener from hackaday.
I wont explain all of the theory or background as it is already explained on cheapvegetablegardener.
I measured the resistance of the sensor in air to be 12Kohms, I then placed the sensor into water (keeping the nail heads above the surface). The resistance dropped to 4Kohms whilst in the water, and then over 20 mins of back in air the resistance rose to 5.6Kohms. The sample still looks and feels quite wet, so I imagine it is going to take some time to dry, but from these prelimary results we can see it appears to work.
Soldering the wires to the nails before creating the plaster of paris along with covering the end sensor with hot glue would improve its longevity. I will post again once I find a better mould to make the plaster in as it was quite difficult to get them out of the cuvettes (I had about a 50% success rate).
Here is a microscope image of the surface of the plaster:
The images are taken with the edge of the camera case pressed right up against the ruler. You could probably remove casing to increase zoom slightly, or create a slot to slide a microscope slide into it. The camera has two focuses the first:
And the second (maximum zoom):
I am using my laptop screen as a typical screen and viewing the image at 100%. Poor mans calculations give you the following for the first focus and second focus:
1mm displayed over 40mm: zoom ~ 40x
1mm displayed over 150mm: zoom ~ 150x
(Note: Measuring magnification level is rubbish as it depends on screen the image is viewed on, so viewing it on a projector would make the statistics seem more impressive.)
The minimum zoom is less than this as we can move the camera further from the object:
Which is about 15x zoom. The microscope box states the zoom is between 10x and 200x, which from these tests seems a little over-exaggerated but not by much.
More microscope image of eyes were requested (by Benjie), trying to focus more on the detail of the eye by using external illumination. Unfortunately the camera has some colour problems when not using the built in LEDs, possibly because it attempts compensates for the lack of illumination. Hopefully I am not in danger of someone cloning my retinal scan to gain access to my confidential files.
So I got a little carried away and started to take images of everything with my microscope:
Note the reflection in the image of my eye, if you zoom in and enhance you may be able to read what is on my screen which will then possibly lead to the solving of a murder.
I’ve wanted a USB microscope for a long time, and I have finally purchased a DigiMicro 200X Zooming USB Digital Microscope from dealextreme (product link) It only cost $40.23 USD (about £27.34 GBP) which I think is quite reasnoble for the fun and cool photos I’m getting out of it.
- Very Cheap
- Easy to setup (plug and play)
- Can take some awesome photos, see below
- Three illumination settings (full on, half on, off) on top of software compensation
- Controls (lights, zoom/focus and snapshot) are located on the body which make using them difficult if you are trying not to move your sample
- The stand is not very stable, tightening it to maximum holds it steady at certain angles for short periods of time
- Takes ~ 2 weeks to arrive from dealextreme as they are based in hong kong
The beauty of this webcam is that it requires no installation with ubuntu 9.10 you simply need to run the software and the camera works! woo! The output of `lsusb` shows the device as:
Bus 001 Device 006: ID 0c45:62e0 Microdia MSI Starcam Racer
and `dmesg` shows the following:
[22844.064666] uvcvideo: Found UVC 1.00 device USB 2.0 Camera (0c45:62e0) [22844.080844] input: USB 2.0 Camera as /devices/pci0000:00/0000:00:0b.1/usb1/1-6/1-6:1.0/input/input9
Most video programs will pick up the device, I am opting to use a program called cheese which is awesome not only because of the name but also because of its simplicity.
sudo apt-get install cheese
Remember to take the lens cap off otherwise you will end up focusing on the plastic cap as shown below. It is fairly obvious if this is the problem as moving the microscope will only change the light levels not the image.
Any requests for microscope images (within reason) will be considered
This page was created for feedback from users of wordcube available via the wordcube website or as an app for android phones (available in market). Filling in these polls and leaving feedback will help improve wordcube for everyone.
Thanks for your feedback. Please post any bugs, suggestions, complaints or ideas below.