[hackspacebristol] Need to extend ADC on Arduino

Marcus Valentine marcus at marcusv.org
Tue Jan 15 22:14:53 UTC 2013


On 14/01/2013 22:11, Matt Hamilton wrote:
>
> On 14 Jan 2013, at 21:36, Nathan Dumont wrote:
>
>> I'd avoid I2C for a run of more than a few centimetres.  It relies
>> on pull up resistors and things and believe it or not the
>> resistance/capacitance of a metre of wire may cause serious
>> problems.
>
> Yeah, that is what I just read.

A few cm seems very pessimistic. I run a LM75 I2C temperature sensor a 
good metre from my Arduino Uno. The I2C bus is only running at 100 kHz 
which is slow enough to allow liberties to be taken.

For RTC for Arduino, check out the Dallas DS1307:

http://www.ladyada.net/learn/breakoutplus/ds1307rtc.html

Many ADCs have a built-in precision voltage reference, so you may not 
need an external precision +5V.

Another solution to dealing with chips in teeny tiny packages is using 
an adaptor board such as those made by Roth Elektronik, available from 
Farnell.

Marcus



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