Sequential Timer Circuit Using NE555

This is a simple sequential timer circuit using NE555 which can be used for psychedelic light, decoration in shops, advertisement boards at night, and parties. The circuit is similar to those published earlier, except for the fact that it incorporates some additional features.

Circuit Description Sequential Timer Using NE555

In the circuit sequential timer circuit IC₂, IC₃ and IC₄ are used as monostable multivibrators. The trigger terminals (pins 2) of these ICs are connected in a chain to the previous ICs through an RC differentiator network (0.022 µF capacitor and 22 KΩ resistors). IC₁ is used as an astable multivibrator with an adjustable duty cycle and period.

To understand the functioning of the sequential timer circuit, supposed the circuit is put in the ‘all rotate’ position and lamp L₁ is on. When lamp L₁ goes to the off state, as pin 3 of IC₂ goes to the low state, it triggers IC₃ through C₉ and R₉ differentiator, and thus lamp L₂ switches on. In the next period, lamp L₂ while going off switches on lamp L₃ and so on, thus completing the chain.

When the switch SW₁ is in an ‘all on’ state, the trigger terminal of each IC₂, IC₃ and IC₄ is clamped to the ground and thus the output of each goes high, making each of the lamps L₁, L_2, and L₃ switch on. This state is useful in checking for fused lamps.

Since IC₁ is put as an astable multivibrator, when switch SW₁ is put to alternate position, for some time the lamps rotate and then for some time all of them glow simultaneously. For the given component values, the period can be increased to about four seconds. This period can be adjusted by VR₁.

The effect on the ‘alternate’ position comes from the fact that in this case trigger terminals of IC₂, IC₃ and IC₄ are put to ‘all on’ and ‘all rotate’ positions automatically alternately because the output of IC₁ goes to Vcc, and ground-level alternately.

Calibration of Sequential Timer Circuit Using NE555

Adjustment of the unit is simple. Put SW₁ to all rotated positions and adjust VR₂, VR_3, and VR₄ so that each lamp glows for equal time, or the effect is most eye-appeasing. Then put the switch to an alternate position and adjust VR₁ for the most pleasing effect.

If many small lamps are to be used, a suitable sequence for connection of the lamps can be L₁ L₂ L₃ L₁ L₂ L₃—–.

Since the monostable IC₂, IC₃ and IC₄ require an initial trigger to be cycling, the circuit may not operates if switch SW₁ is in the ‘all rotate’ position initially. In this case, switch SW₁ to the ‘all on’ or ‘alternate’ position momentarily before switching back to the ‘all rotate’ position.

Check out other decoration project posted in bestengineeringprojects.com

1. Christmas Music and Decoration using Arduino
2. Christmas Decoration Circuit With Music
3. Running and Spellar Effects of Light Circuit

PARTS LIST OF SEQUENTIAL TIMER CIRCUIT USING NE555