contents1. Introduction2. Block diagram3. Circuit diagram4. List of components5. Discription of IC’s6. Working7. Applications8. Advantages9. References10. Conclusion
INTRODUCTION During summer nights, the temperature is initially quite high. As time passes, the temperature starts dropping. Also, after a person falls asleep, the metabolic rate of one’s body decreases . Thus, initially the fan/cooler needs to be run at full speed. As time passes, one has to get up again and again to adjust the speed of the fan or the cooler.
The device presented here makes the fan run at full speed for a predetermined time. The speed is decreased to medium after some time, and to slow later on. After a period of about eight hours, the fan/cooler is switched off.
WORKING The circuit for the automatic speed controller for fans and coolers is shown in the figure. ➢ The supply voltage of 230V, 50Hz is given to the step down transformer and it is convertedto 9V. ➢ The bridge rectifier converts AC to pulsating DC supply and is filtered with smoothingcapacitor. ➢ In the circuit diagram IC1 (555 timer IC) act as an astable multivibrator. It is used togenerate clock pulses. The pulses are fed to a decade divider counter, which is formed byIC2 and IC3. ➢ These ICs act as divide by 10 counters and divide by 9 counters respectively. The valuesof capacitors C1, resister R2 and R2 are so adjusted that the final output of IC3 goes highabout 8hours. ➢ The first two outputs of IC3 (Q0 and Q1) are connected through diode D1 and D2 to the base of the transistor T1. Initially output Q0 is high and there for relay RL1 is energized. Itremains energized when Q1 becomes high. The method of connecting the gadget of the fanor cooler is given in the figure. ➢ Initially the fan shall get A/C supply directly so it shall be run at high speed. When theoutput Q2 becomes high and Q1 becomes low, relay RL1 is turned off and relay RL2 isturned on. ➢ The fan gets A/C through a resistance and its speed drops to medium. This continues untiloutput Q4 is high. When Q4 goes low and Q5 goes high, relay RL3 is activated thus the fanrun at low speed. ➢ Throughout the process, pin 11 of the IC is low, so T4 is cut off, thus keeping T5 insaturation and relay RL4 is on. At the end of the cycle, when pin 11(Q9) becomes high T4get saturated and T5 is cut off. Relay RL4 is switched off, thus switching of the fan or cooler. SSCETEEE DEPARTMENTPage 49 AUTOMATIC SPEED CONTROLLER FOR FANS AND COOLERS ➢ Using the given circuit the fan shall run at high speed for a comparatively lesser time wheneither of Q0 or Q1 output is high. At medium speed it will run for a moderate time periodwhen any of three outputs(Q2 to Q4) is high, while at low speed it will run for a muchlonger time period when any of the four outputs(Q5 to Q8) is high. ➢ It is possible to make the fan run at the three speeds for an equal amount of time byconnecting three terminal decoded outputs of IC3 to each of the transistors T1 to T3. Onecan also get more than three speeds by using an additional relay transistor and associatedcomponents and connecting one or more outputs of IC3 to it. ➢ It has been designed to reduce the amount of electric power. Circuit Diagram: SSCETEEE DEPARTMENTPage 50
APPLICATIONS Used to control the speed of fans and coolers automatically. This device can be used in bed rooms during night hours. This device can be used as a power saving system for hotels and houses
ADVANTAGES No manual support is needed, it is fully automatic. Electrical energy can be saved to a greater extent. Only less power is needed for the operation. Lifetime of fan or coolers can be increased
REFERENCES www.datasheetarchive.com Electronics for you – Magazine www.semiconductor.com www.ecelab.com
CONCLUSION The automatic speed controller for fans or coolers is used to control the speedautomatically. We can also assign different time periods for each speed by designing the circuit tothe need. By using this circuit the electric power can be saved to a greater extent and increaselifespan of fans and coolers.
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