The DIY project posted here is of opto reflector sensor using NE555 and TCRT5000 module. These days opto reflector sensor is used in various project like proximity sensing, position detector, robotics etc. Thus, we had posted a DIY project with working range of 2mm to 10mm.
The module used here is TCRT5000 which have an infrared LED and a photo transistor fabricated internally. The main advantage of using this module is its high-sensitivity and both analog and digital output.
Analog Output: when the module TCRT5000 get reflected IR rays then the output rises from 0V to 3V DC according to the intensity of IR rays falling on it and is analog in nature.
Digital Output: Similarly, when the module TCRT5000 get reflected IR rays then the output rise to logic high (1) from logic low (0) and is digital in nature.
Circuit Description of DIY Opto Reflector Sensor using 555
The circuit of DIY opto reflector sensor using 555 is shown in figure 1 and is built around timer IC 555 and a opto reflector sensor module TCRT5000. Timer IC 555 is configured in monostable multivibrator mode which get trigger from TCRT5000 module. For current limiting of IR
LED fabricated internally to TCRT5000 module a 470Ω (R1) is connected as shown in circuit diagram.
Initially, (i.e. no IR rays detected by module) the trigger pin of IC 555 is high as result output of IC555 is low. But when IR rays is detected by module the internally phototransistor start to conduct which makes transistor T1 start to conduct. Now, the collector voltage of transistor T1 goes low which force trigger pin of IC 555 to goes low. The low voltage at trigger pin (pin 2) of IC1 makes output high for 1 second. The high output makes LED1 glow and drive transistor T2 in conducting state which further makes piezo buzzer to sound. The audio and visual indication (LED and piezo buzzer) indicates opto reflector sensor module receives IR rays.
NOTE: Although sensor module has casing for filter false triggering but sunlight can trigger the circuit. So, testing of circuit must be done inside a room where only artificial light is available.
PARTS LIST OF DIY OPTO REFLECTOR SENSOR USING 555
|Resistors (all ¼-watt, ± 5% Carbon)|
|R1, R3, R6, R7 = 470 Ω
R2, R5 = 10 KΩ
R4 = 1 KΩ
|C1 = 100 µF, 25V (Electrolytic Capacitor)
C2 = 0.01 µF (Ceramic Disc)
|IC1 = TCRT5000 (Opto reflective sensor module)
IC2 = NE555 (Timer IC)
T1, T2 = BC547 (NPN Transistor)
LED1 = 5mm any color LED
4-pin connector for IC1