MCU hanging problem

[chrischristian]

I am using the bulky cassette player motors for my robot and the robot works fine when it is on the black line but as it detects light on either side the whole ckt hangs, the ckt works fine without motors. I thought back emf to be the problem so I tried those 4 diode ckt to reduce the effect of back emf on either side but that has terribly slower down the motor and on one side the hanging problem still persists. 
Don't know what to do ?

Ps.: See the attachments
Ignore the LEDs connecteddirectly to the MCU those were just to make sure that the MCU is working fine, I have removed those.

I have attached 1000uF cap. between GND and +5 of 7805 which is not shown in ckt.

[creedcradle]

Try to use another power source for your Motor driver. As i can see from your schematic diagram , your l293 Vcc is shared to the power source of your PIC. The motor can cause noisy output or voltage/current fluctuations when one of the motor stops or another motor suddenly rotate. Hence, have a separate source for PIC and L293.

-creedcradle

[Admin]

when it is on the black line but as it detects light on either side the whole ckt hangs

What do you mean by 'hangs'?

Beyond your 1000uF cap, you should also put some 10uF ceramic caps both before and after the voltage regulator.