Control devices
Purpose of control devices
A A device that provides an input signal to a circuit to control the functionality. processes the input. When processed, this will cause an output to turn on. Sensors gather measurable data, such as a change in light or temperature, which is collected by a The electronic component within a computer that acts upon the instructions of a computer program. that is programmed with code on how to respond.
Switches
Switches allow Moving electric charges, eg electrons moving through a metal wire. to flow through them when the The metal conducting plates within a switch that are mechanically joined or broken by the switch being pressed. inside are joined together. They are usually named after how they work. For example, a A switch that 'makes' a circuit when pressed. allows current to flow (or a signal to be passed on for processing) when pressed, therefore 鈥榤aking鈥 the circuit. A A switch that 'breaks' a circuit when pressed. does the reverse and 鈥榖reaks鈥 the circuit.
Other examples of switches include:
- reed (magnetic) switch
- rocker switch
- toggle switch
- tilt switch
Image caption, Push-to-make (PTM) and push-to-break (PTB) switch
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Examples of uses for each find of switch may include:
| Type of switch | Uses |
| PTM/PTB switch | Console controller buttons, eg fire or jump |
| Reed (magnetic) switch | Window sensors on alarms, eg window opens and switch contacts open |
| Toggle switch | Power switches |
| Rocker switch | Light switches |
| Tilt switch | To detect if something is no longer level |
| Type of switch | PTM/PTB switch |
|---|---|
| Uses | Console controller buttons, eg fire or jump |
| Type of switch | Reed (magnetic) switch |
|---|---|
| Uses | Window sensors on alarms, eg window opens and switch contacts open |
| Type of switch | Toggle switch |
|---|---|
| Uses | Power switches |
| Type of switch | Rocker switch |
|---|---|
| Uses | Light switches |
| Type of switch | Tilt switch |
|---|---|
| Uses | To detect if something is no longer level |
Transistors
A A device that amplifies an electronic signal made of three layers of semi-conductive material. is a A material that has an electrical conductivity value falling between that of a conductor and an insulator. that amplifies a signal from a sensor - it is like a small electronic switch. Transistors have three legs, A connection on a transistor, when a small voltage passes through the base a larger voltage follows through the other two legs., A connection on a transistor, allowing a large voltage to flow through to the emitter when triggered by the base. and A connection on a transistor, voltage exits at the emitter after entering at the collector..
When a small The potential difference across a cell, electrical supply or electrical component. It is measured in volts (V). at the base connection is detected, the transistor is switched on and a large Moving electric charges, eg electrons moving through a metal wire. can flow in through the collector and out through the emitter.
Advantages
- inexpensive way of improving the sensitivity of a circuit
- can be made a very small size to reduce the size of a circuit
Disadvantages
- sensitive to heat and can be damaged during soldering
Resistor
A resistor allows the resistance in a circuit to be changed by limiting the flow of electric current. Resistors are used in circuits to protect delicate components by controlling the flow of electricity. For example, if too much Moving electric charges, eg electrons moving through a metal wire. flows through a Light-emitting diodes (LEDs) glow when current passes through them. it will be permanently damaged. This use of a resistor protects the LED by limiting the flow of current through it.
Advantages
- resistors are available in a range of values - 0 Ohms (惟) resistors can be used in circuits instead of Used to make connections on a printed circuit board (PCB) where tracks could not be printed.
- used to protect sensitive components by limiting the flow of current through it
Disadvantages
- if the wrong value resistor is installed in a circuit the circuit will not function correctly or may not function at all
Question
Which switch might be used to alert someone a boat may capsize?
A tilt switch because it is activated if it detects something is not level.
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