Week Day Programmable Timer Circuit
Created: Dec 01, 2014
No description available.
This project is a timer circuit that is used for actuating the motor throughout the week as desired by the user. It uses 74HC4017D and 74LV4060D ICs in driving the motor at predetermined time and on preferred days. The 74HC4017D IC is a 5‑stage Johnson decade counter with 10 decoded outputs that has a wide voltage range and with ESD protection. In addition, the 74LV4060D IC is a low-voltage Si-gate CMOS device that has a 14-stage ripple-carry counter/divider and oscillator with three oscillator terminals optimized for low voltage applications.
As shown in the above week day programmable timer circuit, the IC 4060 ais wired up as a 24 hour timer circuit. The time length is determined by the 22uF capacitor and the 10MΩ potentiometer. A suitable fixed value may be selected for these two components for getting the specified time delay. The 22uF capacitor must be non-polar low leakage type of capacitor and the resistors should be MFR 1%.The output is received from pin 3 of U3, which goes high as soon as the set time elapses. This results in a short pulse to pin 14 of the IC 4017 which is configured as a 7 stage counter divider here. With every pulse after the preset 24 hours interval, the IC 4060 also resets itself via the diode connected across its pin 3 and pin 12. The IC 4017 output functions as a week timer where its 7 outputs shift (become high) from pin 3 to pin 6 sequentially in response to the above 24 hour pulses, depicting the 7 days of the week. The IC 4060 at the right side is configured as short duration timer for activating the motor which may be connected with the shown relay contacts. This stage is integrated with the IC 4017 stage through the seven 1N4148 diodes. Depending on what days the motor needs to be switched ON, only those relevant diodes are connected with the 4017 outputs, rest of the diodes are kept unconnected. After all these connections, when power is switched ON, the left hand side 4060 triggers and forces the outputs of the IC 4017 to become high in sequence every after 24 hours. Depending upon the connections of the diodes, the right side of 4060 IC gets switched ON only on those selected days of the week via the BC547 transistor which grounds its reset pin 12 on receiving the signal from the IC 4017 relevant outputs. This prompts its pin 3 to go low activating the preceding relay driver stage and the motor. Moreover, the above stage stays activated until the set time elapses when its output becomes high inhibiting the relay driver sage from base drive thereby stopping the motor. The high from the pin 3 also latches the IC via the diode to its pin 11. The time interval may be fixed by adjusting the given 100kΩ potentiometer and the whole operation resets on the next pulse from the 24 hour 4060 timer stage.
This programmable timer is useful for domestic, commercial as well as industrial applications. It automatically turns on/off the appliance or any electronic device after a preset time, controlling the motors or relays. Furthermore, this can be used in constructing alarm systems that automatically generate an audible sound as predetermined by the user.