motors interfer with microcontroler

[frogeraie]

i use an atmega8 microcontroller digital output to turn on and off a ne555 timer which pulses at 40 khz an ultrasonic transducer. the ne555 shares its 12 vdc power supply with four motors. when the motors start the microcontroller loses its control over the timer. what should i do?
- separate the two power supplies?
- use an optocoupler (how?)?
thanks!

 

[Nahian]

ya....total current must be calculated........
Calculate current for ur 4 motors and added 230mA for each timer and Mc.
Circuit should redesigned..if ur motor take high current like 1A-2A ...make sure that not more than 300mA pass through ur Mc and Ne timer.

 

[DMan]

What about the capacitors as close to ne555 power supply pins as possible? Do you have them? Maybe they can provide a solution.

Have you observed the VDD with oscilloscope? What are the time periods of voltage drops due to the motors?

 

[kender]

- separate the two power supplies?

yes

- use an optocoupler (how?)?

Yes - this is the most reliable approach. You can use optocouplers or other rtypes of galvanic isolation such as magnetic couplers.