How to reduce the effect of electric lighter noise on Micro controller?

Question

I am using a kind of electric lighter in my circuit in order to turn the fire on.

And also i have used some sensors that alert in danger by sending a signal to the MCU (ATmega 32) interrupt. The lighter works with 220 V AC in its input so I used a relay to switch it on and off. Also I used emitter common transistor to make the relay controllable from MCU. Right before it I have used an optocoupler to separate the power supply. But when the lighter starts working, the interrupt program begin and this is my problem.

I have used many methods for example i placed small capacitors on Interrupt's pin, used sound insulation cover around MCU, covering the lighter, covering lighter wires, using ferrite bead (on the output of the power supply of MCU), using big capacitors. They helped me to reduce this noise But not enough to solve my problem. What should I do? Maybe the lighter is too powerful!

Where do MQ2 and MQ5 come from? You want to do the filtering there, not at the MCU pin. — Vince Patron, Aug 05 '17 at 07:24
Have you measured the noise? If so, please post a screenshot of your measurement. — Daniel, Aug 08 '17 at 23:34
@DanielGiesbrecht Not actually. I don't know how to measure it. — Mohammad Reza Hasanpour, Aug 21 '17 at 20:28
@DaneilGiesbrecht Aha. Yes I've checked it. I put prob right on the interrupt pin and i started the circuit but there was no change. Im sure it is not electrical noise. — Mohammad Reza Hasanpour, Aug 23 '17 at 21:38
According to your schematic you are connecting uC ground to igniter ground. Don’t. — Edgar Brown, Feb 23 '19 at 21:12
that capacitor is doing very little of use without a series resistor anyway (except perhaps making the gate output borderline unstable). But as others have said, this is not the place to do it. Clean up the signal coming from the sensor, whatever it is. — danmcb, Oct 29 '19 at 08:06
Does this answer your question? [Use of Flyback Diodes](https://electronics.stackexchange.com/questions/303240/use-of-flyback-diodes) — the busybee, Nov 29 '21 at 10:04

score 0 · Answer 1 · answered Aug 06 '17 at 20:13

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I would try to filter the signals befor U2:A. If you filter it after U2:A such as in the circuit the noise will already have influenced the TTL signal and it can't be differentiated any more if the signal got generated thru noise or the MQ2 / MQ5 modules.

answered Aug 06 '17 at 20:13

elFreak

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Thank you for your suggestion. I'll surely do it and will inform the result here. – Mohammad Reza Hasanpour Aug 07 '17 at 10:55

score 0 · Accepted Answer · answered Dec 12 '21 at 20:53

I checked the signal at the MCU output pin which drives the relay by the oscilloscope. I found that it is not an electrical issue that influences the MCU's interrupts. In my program, I have used an external interrupt (to detect the rising edge of a different signal), and as soon as my ignitor starts to work the interrupt started automatically and sometimes the LCD stopped working and showed weird characters on its screen.

Then I decided to remove those interrupts from my programs and I tried to detect the rising edge simply by checking the input pins at specific times. I tried to use the interrupts as low as possible and I disabled them while working with the ignition system. In this way, I could solve my problem.

How to reduce the effect of electric lighter noise on Micro controller?

2 Answers2