[PD] PD to CV redux (Arduino)

Christian Klippel ck at mamalala.de
Wed Oct 11 22:33:43 CEST 2006

hi steffen,

Am Mittwoch, 11. Oktober 2006 22:11 schrieb Steffen:
> Not to be rude, just noob, what's then the use of the Arduino? I
> mean, why use a Arduino with that chip, if the chip in itself does
> the trick; and what does the Arduino lack in order to do the wanted?

thats easy to answer:
the microcontroller on the arduino does not have a real dac output, but only a 
pwm output. that means you get 0v/+5v signals, just switched in a way that 
the average signal gives a discrete voltage level. due to that technique, you 
have to lowpass-filter the output. this filter in turn limits the minimum 
time between two different levels. also, it adds some kind of glide to it.

oh, and you either have to use the few and resolution-limited channels that 
the controller provides, or you have to write a tight interrupt routine to 
produce the pwm, taking away processing power from other tasks on the 
controller. oh, the linearity is much better as well.

finally you can set a direct relation between the bit-value and the output 
voltage by using a reference voltage. for example, if you use a 4.096 volts 
reference with a 12 bit da, you get exactly 1mV/digit. (altough this can be 
done by a op-amp stage as well).

last but not least, such dac's are exactly for that: to be used in conjunction 
with a microcontroller....

> Thanks for bringing back the topic.
> Best, Steffen



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