http://www.instructables.com/id/Heat-activated-cooler-fan/

Food Living Outside Play Technology Workshop

heat activated cooling fanby sooraj619 on June 12, 2011

Table of Contents

heat activated cooling fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Intro: Heat activated cooling fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 1: Parts list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 2: Circuit diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Step 3: Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

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Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

http://www.instructables.com/id/Heat-activated-cooler-fan/

Intro: Heat activated cooling fanthis a circuit based on the op amp ic 741. this circuit can be used for cooling fans inside pc or an amplifier.it will reduce the unwanted usage of the cooling fans. pleaserate it.........

Image Notes1. LED2. motor3. battery4. 1000uf capacitor5. 2200uf capacitor6. BC 327 transistor7. 741 IC8. thermistor

Step 1: Parts list1 x LM741 IC2 x IC base (holder)1 x 10k thermistor2 x 10K resistor(brown black orange)1 x 1k resistor(brown black red)1 x 680r resistor(blue grey brown)1 x 10k variable resistor (preset)1 x BC327 transistor1 x 1000uf 25v electrolytic capacitor1 x 2200uf 25v electrolytic capacitor1 x a cooler fan or a 12v DC motor1 x common circuit board

Image Notes1. ICbase(holder)2. 741 IC3. transistor base (holder)4. 10K preset

http://www.instructables.com/id/Heat-activated-cooler-fan/

5. LED6. 1000uf 25 v electrolytic capacitor7. 2200uf 35v elctrolytic capacitor8. 9v battery9. battery connector10. common circuit board11. thermister12. 1k resistor13. 10k resistor

Step 2: Circuit diagramcomplete the circuit according to the circuit diagram, the 10K pot is used to change the sensitivity or temperature range, here the transistor BC327 act as the switch, thiscircuit works from a 9 - 12v DC. a filter 2200uf capacitor is provided for a dc source is used from a step down transformer or eliminator.8 pin IC base is used for theIC741. the transistor base or holder is made from the 8pin ic base(holder) by breaking it into two halves of 4pins each and using the three pins for the transistor. this willreduce the burning of transistor when soldering. the LED shows whether the circuit is on or off it is optional

http://www.instructables.com/id/Heat-activated-cooler-fan/

Image Notes1. transistor2. IC holder3. thermistor4. 10k pot

Step 3: Conclusionthis a circuit which helps to reduce the unwanted usage of cooling fans. the thermistor used must be soldered fast without burning the thermistor.never touch thethermistor's black part with soldering iron it will damage the thermistor. instead of cooling fan you can use a relay to control other equipments. hope you like the circuit...and please rate the circuit ,and if you have doubts about the circuit just comment and please rate the instructable

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Comments16 comments Add Comment

ourichie says: Dec 4, 2014. 10:37 PM REPLYI am needing to step down from 12vdc to 5vdc (want to use a small 15mm 5v .06mA fan due to space issues. Adding cooling fan to a Yaesu Ft-1900r hamradio) could I use an l7805 somewhere to charge a 5v cap? I am totally new to this so forgive my ignorance.

sherk2 says: Nov 19, 2014. 8:41 AM REPLYDo we have to heat thermistor to make this circuit work

RITHINROBERT says: Nov 11, 2014. 9:44 AM REPLY

afelix m says: Feb 18, 2014. 12:08 AM REPLYhow to connect the circuit with cooling fan..?

http://www.instructables.com/id/Heat-activated-cooler-fan/

steps39 says: Dec 15, 2012. 7:51 AM REPLYHi, I would like to increase the voltage range of the device 5 - 12V so that the fans turn off completely when the PC is cold and then build up to max at about50 deg is this possible and which resistors control the lower voltage please.

rocketman217 says: Dec 12, 2011. 11:31 PM REPLYwill a 100k thermisistor work?

diy_bloke says: Nov 4, 2012. 6:54 AM REPLYyes it will, but you better increase the resistor with which it makes a voltage divider to 100k as well. With a comparator like this the actual value of theresistors is less important than their relative value

pcline2 says: Jan 20, 2012. 5:35 PM REPLYAbout how much current do you think this circuit would be able to handle?

sooraj619 says: Jan 21, 2012. 6:09 PM REPLYa 12v 3A power supply (max) the 741 IC burned after this

pfred2 says: Dec 13, 2011. 6:29 PM REPLYWhat does the 2200uF capacitor do in the circuit? I hate using those spring IC sockets too. They cause so many problems in projects. They're actually moreexpensive than ICs often too. If I have to socket an IC I use machined turret sockets. They're a lot nicer.

sooraj619 says: Dec 14, 2011. 4:45 PM REPLY2200 uf capacitor is used to reduce ac ripples from a 12v dc transformer when connected as per supply, in case of batteries it is not necessary

pfred2 says: Dec 14, 2011. 6:10 PM REPLYOK. I didn't think it would do much good with a battery.

coolkids says: Jun 28, 2011. 2:07 AM REPLYcan it work just like a cutof in your ac like you set temperature as 24c on your ac and when the 24c is achieved it stops cooling and the blower mode goes onso if excess heat is present in the sorounding then the motor starts working to cool the excess heat

sooraj619 says: Jun 28, 2011. 4:34 PM (removed by author or community request)

sooraj619 says: Jun 29, 2011. 9:08 AM REPLYthe motor that works from 9 - 12v can be used, or use a 9v relay

sooraj619 says: Jun 29, 2011. 9:09 AM REPLYyes