solve the problem of noise

KeithWalker

Joined Jul 10, 2017
1,308
the motor connection is take from the relay board which was attached
The only circuit diagram you have posted is "incubator.pdf". That diagram does not show how the motor and relay are wired. Without that information, we can only make wild guesses at a solution.
 

BobaMosfet

Joined Jul 1, 2009
1,235
i use external interrupt pin on atmega 8(INT1) to do action, but there is a relay and motor in my circuit which activated the interrupt and execute the action. i used switch debounce but no vain how to solve this problem?
You're always going to have noise on ground- cannot be avoided. capacitive/inductive coupling of local utility frequencies alone will cause this. Noise immunity is created by ensuring that your trigger signal has a threshold that is above what is necessary for a logic 1 to be generated on the interrupt pin. Use a capacitor and resistor combination to create a means to 'hold' the signal beyond simple jitters (sample & hold circuit). Which means it take a sustaining pulse to charge the cap enough for it to trigger the interrupt, so you know it's valid. Not a spurious 'noise' signal spike.
 

Thread Starter

mah

Joined Mar 15, 2010
357
here is the relay schematic board. I have already put cap 100nf across the push button and the pin is pull up with 10kohm resistor. what should i do else?
 

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KeithWalker

Joined Jul 10, 2017
1,308
here is the relay schematic board. I have already put cap 100nf across the push button and the pin is pull up with 10kohm resistor. what should i do else?
That looks OK. The interrupt input must be sensitive enough to pick up transients from the relay contacts when the motor is switched. BobaMosfet probably has the solution in the previous posting.
 

Papabravo

Joined Feb 24, 2006
14,702
He mentions that the motor is "a small AC motor". We do not yet know how it is powered so it may not be a very good Idea to connect it to circuit ground.
If the motor ground and the circuit ground have a single common point at the supply it is the best situation without going to full blown isolation which has it's own attendant problems. I understand it migh not be possible to solve the problem with the existing PCB layout. Continuing to use the one he has is just a total waste of time and effort. You can put lipstick on a pig, but it is still a pig.
 
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