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Archive for March, 2010

DIY soil moisture sensors

Mar 28 10
by mat

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.

Plaster of paris humidity sensor

Plaster of paris humidity sensor


Plaster of paris humidity sensor with wires attached

Plaster of paris humidity sensor with wires attached


Both of the sensors

Both of the sensors

I wont explain all of the theory or background as it is already explained on cheapvegetablegardener.

Resistance experiment on moisture sensor

Resistance experiment on moisture sensor

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:

Microscope image of the surface of the plaster of paris

Microscope image of the surface of the plaster of paris

Measurement of microscope capabilities.

Mar 27 10
by mat

As requested (by uplink) here are some images and calculations of the microscopes maximum zoom.

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:

Usb digital microscope's first zoom level of a ruler (markings at 0.5mm)

Usb digital microscope's first zoom level of a ruler (markings at 0.5mm)

And the second (maximum zoom):

Usb digital microscope's full zoom level of a ruler (markings at 0.5mm)

Usb digital microscope's full zoom level of a ruler (markings at 0.5mm)

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:

Usb digital microscope's minimum zoom level of a ruler (markings at 0.5mm)

Usb digital microscope's minimum zoom level of a ruler (markings at 0.5mm)

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.

Microscope images of my eye (by request)

Mar 26 10
by mat

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.

Black and white microscope image of my eye

Black and white microscope image of my eye


Clear reflection of my laptop in a black and white microscope image of my eye

Clear reflection of my laptop in a black and white microscope image of my eye


Coloured illuminated microscope image of my eye

Coloured illuminated microscope image of my eye


Coloured illuminated microscope image of my eye (see the blood vessels)

Coloured illuminated microscope image of my eye (see the blood vessels)

More microscope images (21)

Mar 20 10
by mat

So I got a little carried away and started to take images of everything with my microscope:

Electronics

Magnified image of an intergrated circuit chip

Magnified image of an intergrated circuit chip


Magnified image of an surface mount LED

Magnified image of an surface mount LED


Magnified image of an another integrated circuit chip

Magnified image of an another integrated circuit chip


Magnified image of yet an another integrated circuit chip

Magnified image of yet an another integrated circuit chip


Magnified image of a crocodile clip

Magnified image of a crocodile clip


Magnified image of a surface mounted resistors

Magnified image of a surface mounted resistors


Magnified image of a digital printed circuit board

Magnified image of a digital printed circuit board


Magnified image of a digital camera

Magnified image of a digital camera


Magnified image of a camera focussed on the glass

Magnified image of a camera focussed on the glass


Magnified image of a camera

Magnified image of a camera


Magnified image of a headphone

Magnified image of a headphone


Magnified image of a mobile phone speaker

Magnified image of a mobile phone speaker


Magnifieid image of a DVD

Magnifieid image of a DVD

Materials

Magnified image of a dry sponge (with some solder burns)

Magnified image of a dry sponge (with some solder burns)


Magnified image of a wet sponge (with some solder burns)

Magnified image of a wet sponge (with some solder burns)


Magnified image of a caramel shortbread biscuit

Magnified image of a caramel shortbread biscuit


Magnified image of a flapjack

Magnified image of a flapjack


Magnified image of demin

Magnified image of demin


Magnified image of paper

Magnified image of paper

Eyes

Magnified image of the queen's eye from a £10 note

Magnified image of the queen's eye from a £10 note


Magnified image of an eye

Magnified image of an eye

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.

DigiMicro 200X Zooming USB Digital Microscope in ubuntu (linux)

Mar 20 10
by mat

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.

DigiMicro 200X Zooming USB Digital Microscope

DigiMicro 200X Zooming USB Digital Microscope

Quick Review
Advantages

  • 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

Disadvantages

  • 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

Setup

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

Software
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

Screenshot of cheese webcam software in action

Screenshot of cheese webcam software in action

Lens Cap
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.

Photo of the microscope focussed on its lens cap

Photo of the microscope focussed on its lens cap

Pretty images

200x Microscope image of belly button fluff

200x Microscope image of belly button fluff

Full ~200x zoom microscope image of belly button fluff

Full ~200x zoom microscope image of belly button fluff


200x Microscope image of a £2 coin

200x Microscope image of a £2 coin


Full ~200x zoom magnified section of a £2 coin

Full ~200x zoom magnified section of a £2 coin


200x Microscope image of a custard blob

200x Microscope image of a custard blob


Nonmagnified screenshot of section of screen with the google logo

Nonmagnified screenshot of section of screen with the google logo


200x magnified section of screen with the google logo showing the individual pixels

200x magnified section of screen with the google logo showing the individual pixels


Full ~200x zoom magnified section of screen with the google logo showing the individual pixels

Full ~200x zoom magnified section of screen with the google logo showing the individual pixels


Full ~200x zoom magnified section of my finger

Full ~200x zoom magnified section of my finger


Full ~200x zoom magnified another section of my finger

Full ~200x zoom magnified another section of my finger


Full ~200x zoom magnified section of an LED

Full ~200x zoom magnified section of an LED


Full ~200x zoom magnified section of an LDR

Full ~200x zoom magnified section of an LDR

Any requests for microscope images (within reason) will be considered :)

Wordcube feedback

Mar 11 10
by mat

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