Ultrasonic Sensor Module HCSR04 NE556 The BD139 is a NPN

The BD139 is a NPN complementary low voltage NPN transistor in 3 pin Its package is TO-126

Burglar alarm system

DPDT (Double Pole Double Throw) Rocker Switch is an electromechanical switch which is usually used to control forward and backward motion of a motor

TC4021B is 8 stage parallel in/ serial-out shift register

remote control gate brakes

Ultrasonic Sensor Module HCSR04 NE556 The BD139 is a NPNThis module operates on 5 V DC voltage and 15 mA current. The operating frequency for the sensor is 40 Hz. The minimum range of the module is 2 CM while its maximum range is 400 CM. Accuracy of the reading displayed by the module is 3 MM. 15 is the measuring angle covered by the sensor. This Ultrasonic sensor module has four pins i. e., Vcc, Trigger, Echo and Ground. At Vcc pin, 5 V DC is supplied to power up the sensor. Trigger pin is kept high for