As the name indicates, the step switch selector circuit is intended to choose one of up to four analogue switches, which it does with the aid of some less expensive components. It works off a regulated 5 volt dc supply and draws a current of few milliamperes. It may be used for a variety of applications, such as stepped volume controller, sequential power switcher, and so on. Note that although the prototype uses an ordinary push to on type micro switch, a different kind of sensor may also be used, provided its specification is known and suits the present circuit.
how does the step switch works?
The stepping switch circuit consists basically of a key bouncer, a clock oscillator, 4 stage counter and four analog switches. When power is first applied, the RC network (R5,C4) connected to the reset input (pin15) forces the Q0 output (pin3) of IC2 to be initially active and this standby state is indicated by D2. An oscillator, wired around two gates of IC1, is connected to the clock input(pin 14) of the IC2.
Here, the frequency is near 1Hz with the component values shown (R3=10K & C2=100uF). When S1 is in off state, the counter IC2 remains inactive. If the push to on switch S1 is pressed or when input of the key bouncer circuit( pin11 of IC1) is pulled down, the clock input is enabled at pin 13 of IC2 and the IC counts up at a rate of one count per second.
The counter output state determines the configuration of the four bilateral switches (1 to 4) inside IC3 (4066). When the first pulse is applied to the IC2’s clock input, the Q1 output will be high to trigger switch 1 (IC3A), for the second pulse the Q2 output will be high to trigger switch 2 (IC3B) and so on, sequentially. When the counter reaches its Q5 (pin1) position, the high level at this output resets the counter through resistor R6, switching all bilateral switches of IC3 to off.