In this section, we discus about another application of most popular IC, the 555 timer. Introduced in 1972 by the Signetics Corporation as a bipolar integrated circuit, the 555 is also available in CMOS technology and from a number of manufacturers.
There are various projects we had already posted in timer IC 555 based projects section.
Now, here is project based on 555 which is used as rotational sensor.
When more conveyors or equipment’s are used in process system and any one device fails, there will be accumulation of materials conveyed causing damage to the equipment.
One method for avoiding this is to interlock the driver motors of each equipment. But if the failure is mechanical (for instance, if the drive chain is broken), interlocking system never helps in avoiding such a situation.
Circuit Description of Rotation Sensor Using 555
Here is a simple circuit build around timer IC 555 and a micro switch which senses the rotation of the equipment and when it stops, the complete system is switched off shown in figure 1.
A micro switch is operated by a cam attached to the equipment which senses the rotation. While on rotation, the micro switch charges and discharges the capacitor connected to the pin 6 (threshold terminal) of IC 555 (IC1) thus maintaining the level below 2/3 VCC.
As pin 2 (trigger terminal) of IC 555 (IC1) is clamped to negative rail and pin 4 (reset terminal) of IC 555 (IC1) gets positive pulse, output of the IC will be at high state which energísed a relay through transistor SL 100 (T1). The relay contacts are connected in series to the electrical system driving the motors.
When rotation stops, the moving contact of micro switch will be clamped either to positive rail or to negative rail. If micro switch is at positive rail, the capacitor connected to pin 6 gets charged above 2/3 VCC which brings the output to zero state, switching off the motors connected to it. If it is at negative rail, the reset terminal will be at zero voltage which also bring the output at zero state.
PARTS LIST OF ROTATION SENSOR USING 555
|Resistor (all ¼-watt, ± 5% Carbon)|
|R1, R2 = 10 KΩ
R3 = 4.7 KΩ
|C1 = 1000 µF/25V
C2 = 10 µF/16V
C3 = 0.01 µF
C4 = 100 µF/16V
|IC1 = 555 Timer Circuit
D1 – D4 = 1N4001
T1 = SL100
|X1 = 230V AC Primary to 12V secondary
RL1 = 12V SPDT 100 Ω Relay