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 processor 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 ‘making’ the circuit. A A switch that 'breaks' a circuit when pressed. does the reverse and ‘breaks’ 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 |
Logic gates
Logic gates are process devices. They connect input and output devices. The signals received by logic gates from input devices determine whether the output will be on or off. Different logic gates can be used in combination to design electronic circuits to provide solutions to everyday problems.
AND Gate
The output device will be on if both inputs A and B are on. These are used when you want two conditions to be present for an output to be on. For example, security lights to come on when it is dark AND motion is detected.
OR Gate
The output device will be on if one or both inputs are on. These are used when you want an output device to be on in response to one or two things happening. For example, the internal lights of a car come on when the driver door or passenger door is open.
NOT Gate
A NOT gate has just one input. The output of the circuit will be the opposite of the input. These are used when you want to change the function of an input device. For example, a driver’s seatbelt is NOT clipped in so a warning buzzer sounds.
