Atmega 168pa MCU is not working properly sometimes

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Casper_0770
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Posted by Casper_0770: Sun. Dec 2, 2018 - 05:40 AM
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Hello forum experts,

I am having a problem where I'm trying to run a code that uses PWM and sensors to detect gas. It works perfectly, but mcu detects gas which means that make a beep signal(buzzer) and blinking led without anolog signal (whithout gas ). It repeats 2 or 3 times and after that mcu is silence.
The problem appears when mcu works long time, sometimes 2 weeks or 1 month. It doesn't depend on circuit board.
Does anyone know why this could be happening?

 

This topic has a solution.

sadf

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AVR Microcontrollers, megaAVR and tinyAVR, solved
Last Edited: Tue. Dec 4, 2018 - 02:10 PM
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Kartman
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Posted by Kartman: Sun. Dec 2, 2018 - 07:14 AM
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Could be many things - do you filter your analog signal both in hardware and software? With no filtering a static discharge event (ESD) can cause an invalid reading.  Hopefully this unit isn't a safety device.

 

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Casper_0770
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Posted by Casper_0770: Sun. Dec 2, 2018 - 08:05 AM (Reply to #2)
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I used LM324 op amp for analog signal(10kohm and 47uF). I used two 1000uF 25V 1000uf 10V for converting voltage. I am sure that hardware filter is OK. I didn't solder 0.01uF for MCU(vc,avc and gnd) for ripple because I used high filter.
In software, I used ADC 10 bit for reading anolog signal. How to filter analog signal in software? I used internal oscillator 16 MHz frequency.

sadf

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Kartman
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This reply has been marked as the solution. 
Posted by Kartman: Sun. Dec 2, 2018 - 09:59 AM
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Casper_0770 wrote:
How to filter analog signal in software?

the simplest filter is taking a number of samples and averaging. 

Next up is digital filter using DSP techniques.

 

Casper_0770 wrote:
I didn't solder 0.01uF for MCU(vc,avc and gnd) for ripple because I used high filter.

 

You still need bypass caps for the AVR.

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Brian Fairchild
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Posted by Brian Fairchild: Sun. Dec 2, 2018 - 11:09 AM
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Casper_0770 wrote:

It doesn't depend on circuit board.

 

How do you know? Maybe all your boards are faulty. Show a picture of your board. And also a picture from your PCB CAD program showing the track layout.

#1 This forum helps those that help themselves

#2 All grounds are not created equal

#3 How have you proved that your chip is running at xxMHz?

#4 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand." - Heater's ex-boss

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Casper_0770
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Posted by Casper_0770: Sun. Dec 2, 2018 - 11:44 AM (Reply to #4)
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I considered before it averaging (sensors value/100).
Could you lead digital filter in software?

sadf

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Kartman
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Posted by Kartman: Sun. Dec 2, 2018 - 11:45 AM
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Brian Fairchild wrote:
How do you know? Maybe all your boards are faulty.

Funny how some ignore the obvious!

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DocJC
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Posted by DocJC: Sun. Dec 2, 2018 - 03:28 PM
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Need to also see a schematic of the circuit.

 

The LM324 is not a rail-to-rail op-amp, and if it is running on 5V/Gnd then it has a very narrow window of operation.

 

Need the sensor make and model, (or link), also.

 

When I have had a bug show up once every X hours or days, etc., it has usually been a software problem, where an interrupt just happened to fire at exactly the wrong time to screw things up...

 

JC 

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