Week seven technology project

Hi every one!


I and buddhika found the problem: the relay and bulb. we used a relay and small transistor BC 547, the circuit is working, that is good:

(1) To control the 12V21W bulb is better using the relay (four pins)

(2) We can still using the transistor, the BC 547 is used for the control the relay coils.

(3) The BC 547  base pin received the signal from the 555 ciruit, ( digital type ).

(4) The emitter connects to the ground.

(5) The collector connects to the coil.

(6) The coil first connects to the power supply, let current flow through the coil and then go to the collector.

(7) relay 30 connect to the power, and 87 connect to the bulb.

we made a mistake on the the transistor pins, and we mixture the emitter to the collector. so the circuit is not working, unless the relay is dida----dida, and increasing the voltage to 10.5 volt, the bulb turned on. later we diaganostic the problem, the transistor pin is a problem.