External Hadwear Devices Flashcards
1
Q
How does a digital camera work?
In steps
A
- When a photograph is taken the shutter opens and lets light in through the lens
- The light is focused on to a sensor which is usually either a charge coupled device or a complementary metal oxide semiconductor
- The sensors are made up of millions of transistors, each of which stores the data for one or more pixel
- As the light hits the sensor it is converted into electrons and the amount of charge for each pixel in digital form.
- With light all colours can be made from RGB.
- Therefore to record colour you need three filters one for red one for green and one for blue
- The data is typically stored on removable storage devices usually referred to as flash memory
- Data is typically stored in compressed files eg PNG
- Raw files can also be generated which are uncompressed and therefore contain all the data form the original photograph.
- This digital data can now be decided and manipulated using specialised software
2
Q
How does a barcode reader work?
In steps
A
- A light usually LED or laser is passed over an image
- 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
- 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.
- The waveform is analogue and therefore needs to be converted using an analogue to digital converter
- The encoding will convert the black and white bars into binary codes eg white = 1 black = 0
- The signal is decoded into a form that can then be interpreted by a software
3
Q
How does RFID work?
In steps
A
- RFID Tag: This is a small device, typically attached to an object, containing a microchip and an antenna. The microchip stores information, and the antenna is used to transmit and receive signals.
- RFID Reader/Scanner: This device emits radio waves through an antenna. When the RFID tag comes within range, the tag’s antenna picks up the radio waves emitted by the reader.
- Energy Transfer: If the RFID tag is passive (most common), it doesn’t have its own power source. Instead, it uses the energy from the reader’s radio waves to power its microchip temporarily.
- Data Transfer: Once powered, the RFID tag sends the stored information (such as an ID number) back to the reader using radio waves.
- Reader Receives Information: The RFID reader captures the signal containing the data from the tag, and it decodes the information. This data is then sent to a connected computer or system for further processing, like logging the item’s location or identifying it.
4
Q
How does a laser printer work?
In steps
A
- A rotating drum inside the printer is coated in a chemical which holds an electric charge.
- 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
- As the drum rotates it picks up toner which is attracted to the charged part of the drum
- As the drum rotates it picks up toner which is attracted to the charged part of the drum.
- 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.
- The paper is then heat treated to fuse the toner onto the paper