Timer and Counter Module
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U1 CD4541 is a Timer with Long Duration Ability. This timer is started by a low pulse from earlier circuit, when the temperature goes above setpoint, a low state is at U2A inputs, this starts the timer. The timer output goes high after a preset time. U2C-D Flip flop is power on reset via cap C7. Even a manual ‘reset’ is used if required. This alarm toggle is ‘set’ when The temperature remains high even after the preset time period of U1.
Look no code - How counters and timers were built with traditional cmos logic chips - Up-Down counter-timer
The 74C926 is used here as a four digit counter, The transitions of temperature from earlier circuit, that is the number of times the Process value goes above the Setpoint is recorded in this. A Display switch is given to save power. A reset pushbutton can bring the counter to zero.
Learn how the Frequency Divider 74HCT4040 works. Get a long duration pulse width. Best Pulse Stretching!
A digital counter monitors the number of times a process goes beyond a certain temperature limit over a long cycle of time. This circuit has a Analog Timer and Digital Counter. The Analog timer turns on an Alarm if the Temperature Limit transition is very long.
Learn more about the chips used in this circuit and others who have built similar solutions in varied applications.