Simple relay circuit getting noise spike form AC line

[shripal_javia]

Here is the Sch

Here is the sch...
have a look...

 

[colin55]

Firslty, put a driver transistor on the relay.

 

[shripal_javia]

Improvement in sch

Thanks Colin,
I have made improvement in my circuit as u suggested.
But still I am having same problem.
Controller resets when relay changes its state.

 

[colin55]

1. Put a 2k2 on the base of the transistor and connect the other end to the output of the micro and 100n on the base of the transistor to 0v.

If the above doesn't work. Try the following:

2. Allow the relay to drive another relay that is 30cm away from the PC board.

 

[shripal_javia]

Hi...
1. I have improved my circuit as u suggested. (So now it became as attached)
But it is still having same problem.

2. I have already tested what u have said in second point. it works nicely. but due to less space i cant palce relay so far from MCU.

 

[colin55]

The only other thing you can do is use shielded wires to the motor.

 

[RajinderSandhu]

Dear shripal
please do the following

1) please connect the 100 capacitor between collector and ground (emitter) of the switching transistor
2) bypass rf at the base with a 1nf capacitor as 100nf is too big for the purpose.
3) Also bypass motor power supply with LC pie filter.

 

[dundun]

please help me , i have the same problem too
i currently doing my Final Year Project and i facing this problem , i doing a PIC16F876A to control the desk fan using relay and LCD display , which when i switch on auto mode , the certain relay will switch on according to surrounding temperature , when i not connected my relay circuit to 240 AC desk fan , its work perfectly , i can switch to auto and manual , but once i connected to 240AC desk fan , when i switch to auto mode , i cant control it anymore , and my LCD screen appear many weird wording . i think its AC motor generate noise and disturb get my relay and pic circuit , i had done many thing like put a capacitor at all my circuit , i had put a 0.1uF cap at the AC motor supply , but it still cant work , got any method to overcome this problem?please help me , thanks alot

 

[mneary]

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