Tuesday, October 16, 2007

Evaporative Air Cooler's Pump Controler - Energy Saver

For me, a normal air cooler is a mandatory equipment for surviving the hot summer. This common-man's AC is working on few basic principles (heat is comsumed from air for vapourization of water and air becomes cooler since the latent heat of vaporization of water is very high) but it is a great equipment for common-man. A locally made cooler is normally available for Rs. 2500/- ($55).
I got a new cooler last week, as a electronics enthusiasist, i verified the power consumption and i was shocked by the mesurements. the blower motor is consuming around 300W. and power factor was also very poor. The motor was heating up and i was not able to touch it if it operates for 5 minutes and it was making too much noice also. i decided to replace the motor with a normal table-fan's (i used my bajaj BT-05 for this). The power consumption came down to below 50W!.
In addition to blower motor, the air cooler got another one for pumping the water. but unfortunately i did not get a right replacement for that motor. But i have another justification that it is taking below 100W. Meanwhile, i noticed another big wastage. onces the grills of the cooler is wet, then there is no point in pumping the water to wet the grill again until the wetness reduces. Normally 1/10 of the pump's effort is waisted. so we need a mechanism to switch on the pump periodically so that the grill is always wet.
I picked up a small relay for Rs.20 ($0.5) from a local electronic shop which is normally used in computer monitors and TV sets. it operates on 12V DC. and it to very low rating. so that it can directly driven by the output of the IC 555. You know 555 is capable of loads upto 200mA. i verified that the internal impedence of the relay is high that it takes less than 20mA to operate. i even connected a LED is series with the relay.

here is the diagram!





The simple timer circute with 555 is more than sufficient. The circute i used for my cooler is shown above. Everything is worked perfect. i have few snaps of the assembly (please see below).

With current value of resistor and capacitor (as per diagram), the relay switches on the motor for 30 sec in every 5 minutes.




This simple circut reduces the power consumption to 1/10 th.
You belive it or not! it is working perfectly.


I am attaching few snaps of the assmebled board and my air cooler working with that.








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