How to build a simple Cmos Timer.

COMMENTS SUGGESTIONS	Designing Cmos Timers - Section 2	MORE TIMER CIRCUITS

Cmos Timers Front Page	The Rest of Ron's Circuits	Write To Ron	More Free-to-Use Circuits	Circuit Exchange International

It's assumed that you've read - and understood - the contents of section 1. In this section - we're going to add an automatic reset to Circuits 1 & 2. As before - both timers will begin to run when they are powered-up. But here - the act of switching the power off - will discharge C1 - and so reset the timer.

Circuit No.3


This circuit is exactly the same as Circuit No.1 - except for the reset method.

When Sw1 is switched Off - it connects the two plates of C1 together - through R2.

And this discharges the capacitor.

As before - R2 limits the peak discharge current through the switch contacts.

When Sw1 is switched On - the relay will energize - and the timer will start to run.

When the time period expires - and the relay de-energizes - the standby current is virtually zero.

Section 1 | You Are Here | Section 3 | Section 4 | Section 5

Circuit No.4

This circuit is exactly the same as Circuit No.2 - except for the reset method.

When Sw1 is switched Off - it connects the two plates of C1 together - through R2.

And this discharges the capacitor.

As before - R2 limits the peak discharge current through the switch contacts.

When Sw1 is switched On - the timer will start to run.

When the time period expires - the relay will energize.

Until the relay energizes - the circuit's current consumption is virtually zero.

Section 1 | You Are Here | Section 3 | Section 4 | Section 5

Cmos Timers Front Page	The Rest of Ron's Circuits	Write To Ron	More Free-to-Use Circuits	Circuit Exchange International

Designing Cmos Timers - Section 2

Circuit No.3

Circuit No.4