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Topic: 100K resistors in place of 20K resistors in this DAC??? HELP PLEASE!!!! (Read 1 time) previous topic - next topic

TECH GEEK


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will the 595 work with SPI?

Yes but you will have to pulse the load line yourself after.


i don't understand
As always... Thanks for posting!!!

MarkT


I would use the 470R for the R and two of them in series for the 2R.


That's going to run into issues with the non-zero output impedance of Arduino pins (datasheet suggests this is of order of 40ohms), and also the unknown impedance variation between pins.  Certainly there's no way 12 bit precision can be achieved unless the output impedance is less than 0.1ohm!!

I'd suggest using the 10k resistors instead - if there's enough for about 10 bits that's more precision than can be achieved anyway and at least 10k is going to dwarf the Arduino output pin impedance.

[ I won't respond to messages, use the forum please ]

Grumpy_Mike

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i don't understand

The 595 shift register has a clock, data and load line. The SPI transfer takes care of the clock and data but you need to pulse the line that loads in the latches that are on the end of the shift register once SPI has filled the shift register.

TECH GEEK

As always... Thanks for posting!!!

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