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Description This circuit uses three easily available 555 timer ICs. All three work as astable multivibrators. The first 555 has an on period and off period equal to 1 sec. This IC controls the on/ off periods of the other 2 555s which are used to flash two bulbs through the relay contacts. The flashing occurs at a rate of 4 flashes per second. The diodes are used to protect the 555 ICs from peaks. The relays should have an impedance greater than 50ohms i.e, they should not draw a current more than 200mA. The flashing sequence is as follows: The bulb(s) connected to the first relay flashes for about 1 sec at a rate of 4 flashes per second. Then the bulb(s) connected to the second relay flashes for 1 sec at a rate of 4 flashes per second. Then the cycle repeats. The flashing rates can be varied by changing the capacitors C3 and C5. A higher value gives a lower flashing rate. Note that the values of C3 and C5 should be equal and should be less than that of C1. The value of C1 controls the...

Get the circuit instead of a standard on-off switch. Switching is very gentle. If  we don’t use the PCB, connect unused input pins to an appropriate logic level (‘+’ or ‘-’).  Unused output pins *NEED* be left open!  On the Print Circuit Board this has completed already . One step ’push’ activates the relay, another ‘push’ de-activates the relay. IC1 (the 4069) is a regular Hex-inverter type and is constructed with MOS P-channel and N-channel enhancement mode devices in a single monolithic structure. Alternating On-Off Switch Circuit Diagram : Parts List : R1 = 10K R2 = 100K R3 = 10K R4 = 220 Ohm (optional) C1 = 0.1µF, Ceramic (100nF) C2 = 1µF/16V, Electrolytic D1 = 1N4001 Led1 = Led, 3mm, red (optional) Q1 = 2N4401 (see text) IC1 = 4069, CMOS, Hex Inverter (MC14069UB), or equivalent S1 = Momentary on-switch Ry1 = Relay ) It is going to operate on voltages from 3 to 18 volts, but most applications are in the 5-15 volts.  Although the IC1 4069 contains protection circuitry against...