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

[jjeevan007]

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

 

[wp100]

Hi,

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

 

[jjeevan007]

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............

 

[BradtheRad]

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.

 

[Murugesh_89]

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.

 

[irfan ahmad]

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 .

 

[jjeevan007]

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

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

 

[irfan ahmad]

use lamp for varifying that it is motor noise