I am beginner of robotics and have decided to make my first line follower robot using logic gates ( L7805 and L7812 for voltage regulators, LM339 comparator and L239D

motor driver). i have made all connections an my bread board. At first instance everything seems to be working fine but suddenly i have met with some problems,

1.Voltage regulator 7812 heated up and become unusable(i.e it is not showing correct reading at all)

2.voltage regulator 7805 working some times and not showing readings sometimes( input side reading drops to 1V even i am feeding it with 10V from battery eliminator and

output side shows reading same as input side and i have connected De-coupling capacitors of 0.1μF on each side)

3.7400 posing problems in bread board when I tested it with LED they wont lit up even the output is high and only lit up when corresponding pins are touched with a probe and pin 3 is μshowing continuity with ground.

please tell me if there could be any problem with breadboard itself.
Could anybody please guide me..
Thank you in advance.

 

Hello,

Can you post the complete schematics?
Perhaps also a couple of photos of the build circuit on the bread board.

Bertus

 

More details are definitely in order for this problem to be solved.

Include what voltages are being fed into the regulators, 5 volt and 12 volt. If the input voltage is large or the current draw is significant, as can be expected when running motors, good heat sinking is necessary on the 7805 and 7812 parts...