[help] 12v DC motor noise and back emf elimination

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jjeevan007

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hi to all,

i am doing a project on 8051 which includes the controlling of the 12v DC motor using a relay......

so i need to a help in reducing the noise and back emf which is generated by the DC motor......

regards
jjeevan
 

Hi,

You need to show us the circuit you are using and say what problem the emf is causing ?
 

i dont have the circuit because i didnt design the relay board i brought it from shop............

i am using a ir sensor it is getting saturated because of the back emf or noise produced by the 12v DC motor.........

if i remove the power supply of the 12v DC motor then it works fine............
 

Here is a trick that can assist in filtering out motor noise on a supply wire going to a sensitive device:
Install a resistor between the motor and the device.

Screenshot:



A 22 ohm resistor is shown but this can be adjusted to create the desired effect. The smoothing capacitor can be increased, or a zener diode can be added, etc.

The 2 ohm resistor is a 'token' value which represents a certain amount of internal resistance in the supply.
 

If you connected the relay across the open collector output of NPN transistor then try with adding a free wheeling diode in reverse bias with anode to collector and cathode to Vcc. This would eliminate the back emf generated during relay on and off.
 

1 connect .1uf (104) capacitors to input and output of lm7805 .
2 isolate relay from microcontroller by using optocoupler .
3 use seperate power supply for microcontroller .
 

sorry for the late reply........

i did that but still noise is coming and due this my other circuits are not working properly..........
 

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