741_TIMER

Published:2009/6/29 2:37:00 Author:May | From:SeekIC

R1 and R2 hold the inverting input at half supply voltage. R4 applies feedback to increase the input impedance at pin 3. Pin 3, the nonin-verting input, is connected to the junction of R3 and C. Afterthe switch is opened, C charges via R3. When the capacitor has charged sufficiently for the potential at pin 3 to exceed that at pin 2 the output abruptly changes from 0 V to positive line potential. If reverse polarity operation is required, simply transpose R3 and C. R3 and C can be any values. Time delays from a frac-tion of a second to several hours can be ob-tained by judicious selection. The time delay-independent of supply voltage-is 0.7CR seconds where C is in farads.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Control_Circuit/Time_Control/741_TIMER.html

Print this Page | Comments | Reading(3)