Industrial society: why we need machines
Long ago, one craftsman made a whole thing by hand: slow, and no two were exactly alike. With the Industrial Revolution, steam and then electric machines took over the heavy work. Then came mass production: each worker or machine does one small job, again and again, and many goods are made quickly and cheaply.
Today automation goes one step further: machines with sensors and controllers do the repeated work with little human help. People now design, set up, check and repair these machines.
- Good: more goods, same quality, safer for people.
- Care needed: machines need power, regular repair and trained people, and some jobs change.
Everyday electromechanical devices
An electromechanical device uses electricity to make parts move. Almost every machine at home has these parts:
- Power supply: gives electricity (mains or battery).
- Sensor (input): measures something: water level, temperature, light, position, a button press.
- Controller (brain): reads the sensors and decides what to do. It may be a few relays or a small computer chip (microcontroller, PLC).
- Actuator (output): a motor, a heater, a valve or a lamp that does the work.
- Mechanism: gears, belts, levers and screws that carry the motion to where it is needed.
| Device | Sensor | Actuator |
|---|---|---|
| Washing machine | water level, door | drum motor, pump |
| Lift | floor, door, load | lift motor, door motor |
| Automatic door | motion | door motor |
| Fan with regulator | knob position | fan motor |
Electromechanics and production lines
A production line is a row of stations. A conveyor belt carries the work from one station to the next. At each station a machine does one job: load, drill, paint, check, pack.
Each station repeats sense → decide → act. In our 3D, the sensor spots a faulty box, the controller decides to reject it, and the pusher motor removes it. This is automatic quality inspection.
- Rate: boxes per second = belt speed ÷ gap between boxes.
- The slowest station sets the speed of the whole line. It is a bottleneck.
- Safety: guards, emergency stop buttons and light curtains protect people near moving machines.
- Robots are electromechanical machines too, with many motors and sensors.
Try it: find S-C-A at home
Pick any machine at home: a mixer, a microwave, a toaster, a tube light with a motion sensor. Write three words: its sensor, its controller, its actuator. Some machines have a very simple controller, such as a bimetal strip in an iron. Compare with the 3D: which part is the eyes, which is the brain, and which is the muscle?
Key formulas and definitions
- Rate (boxes/s) = belt speed ÷ gap between boxes
- Good boxes = total boxes − rejected boxes
- Energy (kWh) = power (kW) × time (h)
- Line output = output of the slowest station
Worked examples
1. A washing machine fills water until a sensor says the level is full, then stops the valve and starts the drum. Name the sensor, controller and actuators.
Sensor: water-level sensor (and door sensor). Controller: the control board. Actuators: the water valve, the drum motor and the drain pump.
2. A belt moves at 0.6 m/s and boxes are placed 0.3 m apart. How many boxes pass in one minute?
Rate = 0.6 / 0.3 = 2 boxes per second. In 60 s: 2 × 60 = 120 boxes.
3. A factory makes 500 boxes. The sensor system rejects 15. Find the number of good boxes and the reject percentage.
Good = 500 − 15 = 485. Reject % = 15 / 500 × 100 = 3%.
4. A 0.5 kW motor runs the belt for 8 hours. Find the energy used and the cost at ₹8 per unit (1 unit = 1 kWh).
Energy = 0.5 × 8 = 4 kWh. Cost = 4 × 8 = ₹32.
Common mistakes
- Thinking the sensor decides. A sensor only measures. The controller decides.
- Forgetting the power supply: without it the motor and the controller do nothing.
- Mixing up an actuator (does work) with a sensor (collects information).
- Believing that making one station faster always speeds up the line. Only the slowest station matters.