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Input Output Devices Assignment

This week's assignment was to build an input device. Because my research focuses on irrigation, I thought it could be useful to understand how a soil moisture sensor works and build one. My idea was to send an electric current through the soil, and the resistance and capacitance would change depending on the amount of water in the soil. Soil with higher moisture content should have lower resistance, since water is less resistant than soil.

I started with the transmit-receive step response circuit board provided on the class website here. Milling and stuffing the board went off without a hitch. I'm getting used to this!

For my soil probes, I bought some galvanized steel nails. The nails would probably be conductive enough, but since the rest of my current is traveling along copper, I decided it might be best to stick with the same material and covered the nail with copper (maybe this was irrelevant and unnecessary?). I took some scrap sticky copper meant for the vinyl cutter and wrapped it around my nails.

I connected my nail probes to the PB3 and PB4 pins of my attiny45 microcontroller through the first and fourth pins of the 2x2 connector.

I programmed my board using the transmit-receive code provided on the class website here and the FabISP I built a few weeks ago. I tried using the Cygwin terminal and the make set of commands, but I kept getting errors. I switched to Arduino and my program uploaded without a problem.

To measure the soil moisture I placed my nail probes into a cup of soil and ran the program using one of the IDC's Ubuntu computers (for some reason I couldn't get Python to work on my Windows laptop).

And it worked!

I added some water to the soil and saw the measurement drop:

Well, ok, the measurements displayed here are probably pretty inaccurate. As you can see in the video below, the measurement could not stabilize.

Because the measurement was not stabilizing, I could not calibrate my soil moisture sensor. I had been hoping to match the reading with the amount of water I had put in (water-to-soil ratio by volume), but this was not possible. For my next sensor, I need to figure out how to get a more stable reading.

Files
board traces
board cut-out
soil_moisture.c
hello.txrx.45.py

Computer Input & Output Devices

by Kimberly H. 06/14/2013

Computer Input & Output Devices

by Kimberly H.

1. Examples of Output Devices: Monitor, printer, scanner, speakers, headphones

2. Input Computer Devices

2.1. Benefits of input devices include the ability to enter data to be stored for future retreival, the ability to make photo quality printouts and the abiliyt to use pointing devices equipped with assistive techonogy for sutdents with disabiliteis.

2.1.1. Challenges that may relate to input devices aret compuer monitor screen resolution and the use of keyboards for students with movement disabilities. The use of assistive technology would help to accommodate students who cannot use keyboards and monitors in the classroom

2.2. Application: Keyboards and mice would be used in the classroom along with computes to allow students to enter data into the computer to complete assignments as required

3. Examples of Input Devices include: Keyboards, scanners, trackball, mouse, digital media resources

3.1. Trackballs could be used in the classroom for students with disabilites or those students requiring the use of trackball due to hand movement or cordination disabiliteies.

4. Output Computer Devices

4.1. Output devices are used to communicate information or data out of the computer to the user. Output devices work to link visual images and auditory information to the user

4.2. The benefits of output devices include the communication of data between the user and the computer, the abiliyt for the user to see visual images and hear sound from the computer. Input devices would allow student in the classroom to hear music being played as part of an assignment. Output devices may also alow students to print data.

4.3. Challenges with output devices may include the inability for students with disabilities to use a keyboard or trackball. Thee use of a microphone may be an appropriate assistive technology device. Another challenge may be the inability to see touch screens or montors. Voice applications could provide asstance for students who may be blind or have difficulty seeing text on a computer monitor

5. Digital media sources such as a camera could be used for students to upload pictures on the computer to provide visuals and graphics for projects and assignmen

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