connect DC FAN on inverter which use charging LED an on/off switch

Dear experts,

There is an idea click on my mind. i have a local inverter and i want to connect a DC fan on this. there is a huge power cut in our city and i set 24 amp charging on it. but it's effect transformer is excessive heat to prevent this condition i want to connect a DC fan on it's charging LED when charging LED is glowing off fan automatically off. can any one send to me suggestion for same and how i connect a DC fan ( 12v 0.12 AMP rating ) using LED in way of on/off switch. my thought on it a transistor is using for fan operation which base use LED in form of on/off switch. kindly suggest.

hi elanshul,
i am giving you complete solution,,,,
you cant drive transistor base from the current going to led,, all u have to do is to first use a comparator ,ic741,,, now i'll tell u how comparator circuit works in ic741, when pottential at pin no.3 is greater than pin no.2 the output will be high,(10 volts) ,, now make a voltage divider circuit through resistances and give a pottential of 1volt to pin no,2,
now connect the pin no,3 of the ic to the +ve terminal of the led, ,,, dont forget to common the ground, till now your circuit will work like this, when charging led is on the ic741 output will be 10 volts,,, and when the charging led is off , u will get the low output at the ic 741 (pin 6),,, now u have to take a n type mosfet (irf540 , or irfz44), and connect its gate to the ic741 output i.e pin no. 6,,,, source will be grounded , and fan's positive terminal is pemanently connected to 12v supply and fan's negative terminal will be connected to the drain terminal of the mosfet,,,use 10 ohm resistance at the gate , and 1k from gate to source,,, now u r done,, your circuit will work perfectly ,,,








Best Wishes
--BawA--