Help on delay for the 4060 oscillator used in the fridge door alarm project

[edwardgith]

            Hi, i have been studying the datasheet for the 4060 counter and oscillator used in the fridge door alarm project found in this website.I have tried to read the datasheet and i have seen that the delay time is obtained by the equation (2.2Rc*Cc).On substituting the values of C1 and R3, i don't get the value of 20 seconds.Could you please assist me?The datasheet is found in www.datasheetsarchive.com           
Also i would like to use the fridge door alarm to activate a motor that will actually close the fridge door alarm.Could you please lead me to a place where one can learn about motors.

 

[audioguru2]

The Cmos oscillator needs an Rs added as shown on datasheets. It should be 10 times the value of the frequency-determining capacitor for the formula to be fairly accurate.

The Cmos ICs have an absolute minimum operating voltage of 3V. If the battery voltage is less than 3V then the oscillator might fail to operate properly.

I don't think you'll find a 3V motor strong enough to close the door. If you use a 12V power supply or battery for the project then it could use a car's window-winding or wipers motor and gearbox. The motor's current will be much higher than the rating for the project's little transistor so a power transistor will be needed to be added. ;D

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