Here is a circuit used to control motor more efficiently than any electromechanically controlling device. The project shown here is cheap and easy to construct. It also overcome the problem of noise triggering and noise pulse.

Circuit description

The power supply is given by pressing switch SW₁ it shots the N/O contact of relay RL_­1 which gives supply to the circuit. The current through resistor R₈ gives the base current to transistor T₅. Where transistor T₁, T₂ and T₃ from the over and under-voltage cut-offs. Here the transistor T₄ on when over or under voltage is given to transistor T₃.

For avoiding noise capacitor C₂ with resistor R₁₀ form a loss-pass filter and also give sufficient time delay. Here the resistor network (R₁₁, R₁₂, VR₁) are used as current sensor. Where Diode D₃ is as rectifier and capacitor C₁ is used as noise filter of switching circuit.

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R₁ = 150 KΩ

R₂ = 33 KΩ

R₃ = 6.7 KΩ

R₄ = 100 KΩ

R₅ = 39 KΩ

R₆ = 15 KΩ

R₇ = 10 KΩ

R₈ = 4.7 KΩ

R₉ = 75 Ω/1W

R₁₀, R₁₃ = 47 KΩ

R₁₁ = 470 Ω

R₁₂ = 0.5 Ω

VR₁ = 2.2 KΩ

Capacitors

C₁ = 1000 µF/25V

C₂, C₃ = 47 µF/10V

Semiconductors

T₁, T₂, T₃, T₄ = BC148

T₅ = SL100

D₁, D₂, D₃ = 1N4001

ZD₁, ZD₂ = 3.1V

ZD₃ = 9.1V

Miscellaneous

SW₁, SW₂ = Push to on switch

X₁ = 230 primary AC primary to 18-0-18, 500mA secondary transformer

OR

(110 primary AC primary to 18-0-18, 500mA secondary transformer)

RL₁ = 12V, 200 Ω Double pole double throw

M = Motor