555 household time-limit alarm circuit

Published:2011/6/7 2:25:00 Author:TaoXi | Keyword: 555, household, time-limit, alarm | From:SeekIC

As the figure 15-15 shows, the preset timer uses one piece of dual time-base 556 and one piece of 555 as the core. The preset time is 5 to 30 minutes, when the time is up, this circuit will send out the sound-light alarm signal, and after a few minutes, this circuit will cut off the power automaticly. It can be used to control all sorts of home appliances. The RP1, R1, C1 and 1/2 556 can be used in the 5 to 30 minutes boot timing. When the power supply opens, the C1's electric potential can not be mutated, so the timing circuit sets and the timeing starts, the timing time td1=1.1(RP1+R1)C1, you can change the timing length by adjusting RP1. The monostable delay circuit is composed of the RP2, C2 and another half of 556, the delay time depends on the time constants of RP2 and C2.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Control_Circuit/555_household_time_limit_alarm_circuit.html

Print this Page | Comments | Reading(3)