I believe testing circuits are a must for project geeks since these testers save so much of time in debugging circuits. People invest all their efforts and spend so much of time to complete one project but most of the time they don’t get the desired output. There can be multiple reasons behind this and generally it is because the components like servo motors are at fault.
The project Servo Motor Tester Circuit Using 555 IC used in the project after isolating it from the project and help us to detect if the problem lies in the motor or the circuit logic.
Circuit Description and Working of Servo Motor Tester Circuit Using 555 IC
The Servo Motor Tester Circuit Using 555 IC passes pulses of varying width to the motor attached with the circuit and then monitors the output of the motor and evaluates the angle to which it turns in respect to the input fed to the motor. For instance, if we supply a 1.5ms pulse input to the motor, it should turn to a neutral position i.e. 90 degree position.
To avoid any chances of failure, the project Servo Motor Tester Circuit Using 555 IC feds pulses of varying widths to the motor. The circuit uses two NE555 timer ICs; IC1 and IC2 along with few other discrete components to generate width varying input pulses. IC1 is used as an astable multivibrator and has time period of 20 ms.This IC also triggers IC2 at the end of 20 ms. It does so by generating a sharp negative pulse. Similarly, IC2 is employed as a monostable multivibrator that produces pulses of different duration; 1 ms, 1.5 ms and 2 ms so as to feed the servo motor and monitor its output accordingly.
Pull down resistor R2 is connected at the pin 4 of IC1. Switch S1 and S2 are also included in the circuit. As the switch S1 is closed, astable multivibrator (IC1) triggers the second IC i.e.IC2 to generate a pulse corresponding to the position of the switch S2 in the circuit. As shown in the circuit diagram, switch S2 can be used to connect any resistors R4, R5 and R6 or all of them, and R7 to develop monostable output pulse of different intervals: 1ms, 1.5 ms or 2 ms respectively. The time period of IC1 is fixed at 20 ms by a preset VR1.
Once the circuit is assembled, select the appropriate resistor and choose the monostable input as 1ms, 1.5 ms or 2 ms. After that close the switch S1. On doing so, the servo motor must rotate either to the extreme left, middle or extreme right direction as per the input fed from the circuit to the motor.
PARTS LIST OF SERVO MOTOR TESTER CIRCUIT USING 555 IC
|Resistor (all ¼-watt, ± 5% Carbon)|
|R1, R5 = 12 KΩ
R2 = 5 KΩ
R3 = 100 KΩ
R4, R8 = 10 KΩ
R6 = 2 KΩ
R7 = 18 KΩ
VR1 = 10 KΩ
|C1 = 1 µF/16V
C2 = 0.01 nF
C3 – C6 = 0.1 µF
C7 = 1000 µF/25V
|IC1, IC2 = NE555
IC3 = LM7805
D1 = 1N4148
D2, D3 = 1N4007
|X1 = 230V AC Primary to 6V – 0 – 6V, 500Ma Secondary Transformer
SW1 = PUSH-TO-ON Switch
SW2 = Three-Way Rotary Switch
M1 = Servo Motor