Run ADC on ATMega1280...???

Ajaxelectronic · Joined: 22 Nov 2009 Posts: 171 Location: Iran

Hi

how can we run ADC in the ATMega1280A chip?

i wrote a code. it work in proteus but not work in real, i get random value between 258 to 385 only. my hardware is right. i have 10uH inductor and 100nF capacitor for LCP in AVCC. AVcc and Aref pins are connected together.

i test my code with of f, Avcc, Aref, internal_1.1 and internal_2.56 for my reference voltage, but not work none.

this is my code :

i.dobson · Posted: Wed Sep 28, 2016 3:23 pm Post subject:

Hi,

I'm also using a mega1280 and don't have any problems with the adc. I'm using:-

Ajaxelectronic · Joined: 22 Nov 2009 Posts: 171 Location: Iran

Hi i.dobson

thanks alot. i try your code. but it doesn't work for me. Crying or Very sad

Ajaxelectronic · Joined: 22 Nov 2009 Posts: 171 Location: Iran

yes...

my chip was corrupted. i change my chip and it work now.

other question. what is the best way for measuring effective voltage of a pulse train? this pulse frequency changing between 150Hz to 10KHz.

i.dobson · Posted: Wed Sep 28, 2016 6:06 pm Post subject:

Hi,

Do you want to measure the "average voltage" or the frequency of the pulse?

For average voltage you could use a RC filter (resistor & capacitor)
For frequency maybe try using an Interrupt Input that fires on a rising or falling edge, and Count the number of pluses per second.

Regards
Ian Dobson

Ajaxelectronic · Joined: 22 Nov 2009 Posts: 171 Location: Iran

yes, i want to measure average voltage and frequency. i measure frequency and don't have problem with it. but in measuring average voltage i have problem.

i not use RC filter yet. what is R and C value? i think it depend on frequency but we have a wide range of frequency(150Hz to 10Khz).

how can we calculate R and C value?

i.dobson · Posted: Thu Sep 29, 2016 11:14 am Post subject:

Hi,

Have a look here http://sim.okawa-denshi.jp/en/CRtool.php that should help you calculate the correct values for R&C.

Regards
Ian Dobson

Ajaxelectronic · Joined: 22 Nov 2009 Posts: 171 Location: Iran

thank you i.dobson

i calculate my R and C value for this low pass filter. but it can pass my frequency just. my problem is my ADC value does change very very fast and i don't have a steady state for ADC value.

i.dobson · Posted: Sat Oct 01, 2016 7:19 am Post subject:

Hi,

Maybe try increasing the value of C. Also try measurung the voltage with a Volt meter. You might Need to use a Software filter on the AVR (have a look here for a good example http://www.mcselec.com/index2.php?option=com_forum&Itemid=59&page=viewtopic&t=13285&highlight=smoothing ).

Regards
Ian Dobson

Ajaxelectronic · Joined: 22 Nov 2009 Posts: 171 Location: Iran

thanks a lot

i buy an IC for convert RMS to Dc value. my chip is AD736 and i want to running it. i thinks this is better way.

thanks again