Guest r816wsd Posted March 10, 2004 Report Share Posted March 10, 2004 could anyone explain how the fridge door alarm circuit works in technical terms. How does the 6040 IC workProject Link: http://www.electronics-lab.com/projects/sensors/011/index.html Quote Link to comment Share on other sites More sharing options...
mixos Posted March 10, 2004 Report Share Posted March 10, 2004 The above circuit uses the CD4060 IC which is a binary counter. I attach you the datasheet.CD4060BC.pdf Quote Link to comment Share on other sites More sharing options...
mixos Posted March 11, 2004 Report Share Posted March 11, 2004 Fridge door Alarm http://www.electronics-lab.com/projects/sensors/011/index.html Explanation (based on the existing explanation):With the door closed the interior of the fridge is in the dark, the photo resistor R2 has a high resistance (>200K) thus clamping IC1 by holding pin 12 which is the RESET PIN at high logical state (logical 1) so the internal counters don't count and all output pins (Qx) are at logical 0.Pin 12 has a voltage [R2/(R1+R2)]*VDD where VDD is the battery voltage. The result is a volatge close to VDD which is a logical 1 and clamping 4060 to reset state.When a beam of light enters from the opening, or the fridge lamp lights, the photo resistor lowers its resistance (<2K), pin 12 goes low (0 logical state) and IC1 starts counting.IC1 starts counting means that the internal oscillator goes ON and it is producing a square wave with a frequency which is set by R3, C1 and give out from the form (depending on datasheet):f=1/(2,2*C1*R3) => f=454 HzThis square wave is taken out from Q14 with a result frequency f/(2^14) and from Q7 with f/(2^7) So the output waves Q14 and Q7 look like this:after a preset delay (around 20 seconds in this case) the piezo sounder beeps for 20 sec because the low output of Q14 makes D1 ON =>Q1 ON. Then stops for the same lapse of time (Q14 is in high state and D1 is OFF => Q1 is OFF) and the cycle repeats until the fridge door closes. D2 connected to pin 6 of IC1 makes the piezo sounder beeping 3 times per second. Quote Link to comment Share on other sites More sharing options...
irabot Posted December 11, 2005 Report Share Posted December 11, 2005 I have completed the fridge alarm circuit and i have problems. The buzzer keeps sounding even with r2 in or out can someone help me??Ivan Quote Link to comment Share on other sites More sharing options...
audioguru Posted December 11, 2005 Report Share Posted December 11, 2005 Hi Ivan,Welcome to out forum. ;DAre the diodes installed backwards?Are the pins of the transistor wired properly? Quote Link to comment Share on other sites More sharing options...
logan_dslasher Posted February 9, 2006 Report Share Posted February 9, 2006 excuse me, may i butt in? audioguru? you have just showed a BC337 pin configuration. that's the same transistor i am using in the whistle responder right? all this time i thought that the first pin is the emitter... this could be the reason why i can;t get the project to work.. Quote Link to comment Share on other sites More sharing options...
audioguru Posted February 9, 2006 Report Share Posted February 9, 2006 Transistors operate much better when they are wired correctly. Quote Link to comment Share on other sites More sharing options...
ZaZo4EvEr Posted March 18, 2007 Report Share Posted March 18, 2007 Hey every body i've tried to build this circuit but the problem that i faced is that the sound of beeping is too low can someone help me to fix this error Quote Link to comment Share on other sites More sharing options...
audioguru Posted March 18, 2007 Report Share Posted March 18, 2007 If you use brand new alkaline battery cells then the supply voltage is only 3.0V and the beeper gets only about 2.2V from the emitter-follower transistor. A beeper barely works with only 2.2V.Use a 6V, 9V or a 12V battery and it will be much louder. Quote Link to comment Share on other sites More sharing options...
ZaZo4EvEr Posted March 23, 2007 Report Share Posted March 23, 2007 I used a 9V battery but I still have this problem.Can you pist to me a picture of Piezo Sounder may the problem in it.I may bought a wrong device..Can you send your replay via e-mail plz....[email protected] Quote Link to comment Share on other sites More sharing options...
audioguru Posted March 23, 2007 Report Share Posted March 23, 2007 It is a piezo beeper with a built-in oscillator. When the circuit applies a voltage to it then it beeps. The circuit makes a delay then makes the piezo beep 3 times per second.With only a 3V battery it will not be loud.With a 9V battery then it should be much louder. if the transistor is connected backwards then it will not be loud. Look on the datasheet for the transistor to see which pin does what.A piezo speaker looks similar but doesn't have a built-in osccillator so it would just make a faint clicking sound in this circuit. Quote Link to comment Share on other sites More sharing options...
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