External Hadwear Devices

Question 1

How does a digital camera work?
In steps

Answer 1

1. When a photograph is taken the shutter opens and lets light in through the lens
2. The light is focused on to a sensor which is usually either a charge coupled device or a complementary metal oxide semiconductor
3. The sensors are made up of millions of transistors, each of which stores the data for one or more pixel
4. As the light hits the sensor it is converted into electrons and the amount of charge for each pixel in digital form.
5. With light all colours can be made from RGB.
6. Therefore to record colour you need three filters one for red one for green and one for blue
7. The data is typically stored on removable storage devices usually referred to as flash memory
8. Data is typically stored in compressed files eg PNG
9. Raw files can also be generated which are uncompressed and therefore contain all the data form the original photograph.
10. This digital data can now be decided and manipulated using specialised software

Question 2

How does a barcode reader work?
In steps

Answer 2

1. A light usually LED or laser is passed over an image
2. Some form of light sensor is used to measure the intensity of light being reflected back. Thks is converted into a currently effectively generating a waveform. Thks could be achieved using a photodiode or a CCD sensor
3. White areas reflect the most and the black the least making it possible to use the waveform to distinguish the patterns of black and white bars.
4. The waveform is analogue and therefore needs to be converted using an analogue to digital converter
5. The encoding will convert the black and white bars into binary codes eg white = 1 black = 0
6. The signal is decoded into a form that can then be interpreted by a software

Question 3

How does RFID work?
In steps

Answer 3

1. The tag contains a chip which contains the data about the item and a modem to modulate and demodulate radio signals
2. The tag also contains an antennae to send and receive signals
3. Tags can be either active, where they have their own source of power in the form of a small battery, or passive which means they will pick up electromagnetic power when they are in the range of a RFID reader
4. Signals and therefore data can be transmitted in both directions using radio frequencies this can be over long or short distances depending on what the tags are being used for and how they are powered
5. Tags may be used simply to track the physical location of the tagged item or the item may transmit data back

Question 4

How does a laser printer work?
In steps

Answer 4

1. A rotating drum inside the printer is coated in a chemical which holds an electric charge.
2. The laser beam is reflected onto the drum and where the light hits the drum the charge is discharged effectively creating the image on the drum
3. As the drum rotates it picks up toner which is attracted to the charged part of the drum
4. As the drum rotates it picks up toner which is attracted to the charged part of the drum.
5. Paper is passed over the drum and by charging the paper with the opposite charge to the toner the toner is attracted to the paper and away from the drum.
6. The paper is then heat treated to fuse the toner onto the paper