Electronics > Beginners
DC Motor 10V - Creates noise in power line
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2X:
Hello,
I have the below timer swich with NE555 timer on my breadboard and when I connect the DC motor at the tranzistor (BD139) the output stays high only for 1sec instead of 24seconds. If I connect a capacitor "C4" 220nF or 1uF parallel with the motor the output stays ON approximately 19sec which again is not right. I connect the oscilloscope at the power line and I saw spikes even with tha parallel capacitor with the motor. Does anyone know how can I solve this problem (I don't want to use mosfet or optocoupler)?
rstofer:
You can try putting a 0.1 ufd capacitor right at the motor terminals.  DC brushed motors are always noisy.
Paul Price:
Put a 100uF paralleled with a .1uF directly from the + motor terminal to ground.

How do you checked for 24-Sec timing with the motor disconnected?
2X:

--- Quote from: Paul Price on May 15, 2018, 09:36:18 pm ---Put a 100uF paralleled with a .1uF directly from the + motor terminal to ground.

How do you checked for 24-Sec timing with the motor disconnected?

--- End quote ---

I connected at the output (pin 3) of the 555 a LEDwith a resistor 330ohm.
Benta:
As rstofer says, DC motors are noisy.
A good way of silencing them is 100 nF across the motor terminals and 2 x 22 nF from each motor terminal to motor case.
All three caps should sit directly on the motor.
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