34. Arduino for Production! AVR Atmega32 - Measuring the ADC Noise (ADC Noise Reduction Mode)

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In this video, we go a little further and investigate the noise in the ADC. We measure the deflection from one sample (conversion) to the next and add it all up. I also introduce the ADC Noise Reduction Mode. All test used the Accelerometer.
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Опубликовано:

7 дек 2011

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Комментарии : 28

@ganeshmirajkar 11 лет назад

My PCB is done finally and i measured the defections. Its from 140 to 160 over 500 samples. I have a 200uf cap on 3.3v supply and I have also added a 4.7uf cap between adc_gnd and aref just to make sure no noise enters from aref.

@ganeshmirajkar 12 лет назад

Yup. I agree totally. Even I did not get different results. Once I am done with my project in which I will be using my custom made PCB I will share results with you.... By the way, your atmega tutorial videos are just great...!!!

@PatrickHoodDaniel 12 лет назад

@SajjadBro This is correct from my experience. I have been following the datasheet as closely as possible to reduce noise. Note that I didn't use an inductor as is specified on the datasheet, and this may have an effect on the accuracy. I have not received any comments from folks that may have had better results. Atmel does publish a paper for 12bit resolution, but I have not read the paper (skimmed it).

@PatrickHoodDaniel 12 лет назад

Thanks. Yes, please share the results.

@PatrickHoodDaniel 11 лет назад

Ah yes, I understand. It's been a long time since I did this video. I need to watch my video again. :))

@PatrickHoodDaniel 12 лет назад

@imp1us Yes, I know this, but I try to stay away from other written functions so I can reduce the overhead on these microcontrollers.

@imon4mRUET 2 года назад

thank you.

@PatrickHoodDaniel 12 лет назад

I did test the sleep mode as well, but also saw no difference. I probably wont introduce this concept until I can get better results.

@neighborshomeremodeling 9 лет назад

Patrick, I realize this is an old post, but thank you. very informative. Question... What was the source of the analog being measured? was it pure DC? since the larger cap and the sleep mode did not show any improvement, could the noise actually be from the source? Thanks again.

@PatrickHoodDaniel 12 лет назад

@SajjadBro I'm left handed. :))

@PatrickHoodDaniel 11 лет назад

The 140-160 is the digital unit returned by the ADC?

@ganeshmirajkar 12 лет назад

I think for noise canceler we also need to call the SLEEP command. In the code i removed start conversion command in ISR routine and also above while loop. Instead I added a sleep command in while loop. In noise canceler mode if SE is set in MCUCR, UC will go in sleep mode when sleep command is executed and also will start a conversion. Unfortunately I did not see much difference.

@PatrickHoodDaniel 12 лет назад

@kratok2006 Excellent!!

@blah148 7 лет назад

Curious what IDE you use?

@damienlawrence7858 9 лет назад

AC Voltage 120V up to 277V

@shashankmore321 8 лет назад

when i send a signal of say 90 mv from the voltage divider circuit to ADC(10 bit) then the ADC result is 0.But the result should be around 18 (Vref=5v).Can u please tell me the reason......I just wanted to make my circuit such that if i give 5mv then ADC result should be 1. PLEASE rpely ASAP....

@ganeshmirajkar 12 лет назад

But following two things brought my deflection down to 200-250 1: Adding a 4.7electrolytic cap between aref and ground(even if using 2.56 vref) 2. Added a 220Uf electrolytic cap near to accelerometer vss and vcc.

@ObstTube 7 лет назад

I think you shouldn't add the first deflection because it is wrong (theTenBitResults - 0). Is it true? (look ie. at 20:35 )

@damienlawrence7858 9 лет назад

So if I have to test voltage how can I do it ...... If you can show me that like a dummy OK

@ganeshmirajkar 11 лет назад

I mean the total_deflection. This deflection is added over 500 samples instead of 100

@RitwikG 8 лет назад

Hi, A small doubt. I dont know if anyone has asked it before. @8:12 in your video inside if condititon, cant I just put deflectio *= -1? Is there any problem if I do like that?

@RitwikG 8 лет назад

Also if you dont mind can you tell what is the difference between deflection with noise reduction mode and without noise reduction mode without any capacitor

@ilovekheti2812 Год назад

Hello sir i am using stm32 f401 black pill but ADC value fluctuate a lot even on dc input, how to improve it thanks

@PatrickHoodDaniel Год назад

The only way I know to improve this is to create a special ground plane for the ADC. This is relevant for the AVR. I have DC projects in my book that showed good results, and in my ADV STM32 videos. You may want to check those out. Look for my STM32 ARM older video series where I show how to use the ADC.

@daviddickey9832 Год назад

Is it normal that your adc is showing 300-350 out of 1024 with nothing plugged in? That seems really high.

@PatrickHoodDaniel Год назад

Hey David, quite observant. Haha. The deflection is the better way to judge the ADC in this prototyping environment, the impedance on the vast amount of metal in breadboards, all the other challenges along with prototyping, and the lack of analog ground separation can cause these values. The ADC is measuring the analog signal and if there is impedance, the value will not be close to zero especially when all of that metal is serving more as an antenna rather than a good conductor. When the ADC is used in a PCB that follows the design rules of: analog ground separation, short traces to eliminate as much imediance as possible with good trace separation, the ADC values will be far better.

@iyadsaleh3695 9 лет назад

thank you you are great teacher but here i think you miss SLEEP instruction { .... sleep_enable(); sei(); while(1){ sleep_cpu();//here start conversion and sleep