Microcontroller, LED, DC motor problems

[Superposed_Cat]

Hey all, me and my friend are attempting to control a 5v dc motor and make a LED blink simultaneously using a H-Bridge Motor Driver 1A - SN754410 and ATMEGA328 micro-controller(16mhz, 8bit). The issue is is that when my H-Bridge activates the motor using input from the micro-controller then the blinking light blinks faster, almost solidly. The actual program cycle seems shorter.Perhaps the cpu is bugging out due to lack of voltage. Any help appreciated, thanks.

 

[donpacino]

Do you have an external power supply or the micro-controller supplying the voltage to the H-bridge?

 

[Hesch]

How do you make the LED blink? Internal timer in the microcontroller?

Often such timers can be configured for internal/external enable signal etc., and as you start the dc-motor, the switch noise may affect an inputpin for the timer. For example a weak (internal) pull-up resistor may not be strong enough to keep an inputpin high, or you may have configured the timer unintentional.

 

[Windadct]

Are you using timer 0?

 

[Superposed_Cat]

Sorry forgot to mention I we fixed it, we just used a capacitor to smooth out the voltage, I don't know what caused the fluctuation but it worked.

 

[donpacino]

Sorry forgot to mention I we fixed it, we just used a capacitor to smooth out the voltage, I don't know what caused the fluctuation but it worked.

you aretalking about a decoupling capacitor on the microcontroller input?
Yous should ALLWAYs have decoupling capacitors on switching device inputs. Think about it. there is inrush whenever a transistor switches on or off, which will change the current draw. A microcontroller has a poopton of transistors.