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kevinj
08-15-2005, 04:08 AM
I was reading the DAC tutorial, and came across,
The typical method for choosing how many cycles to charge is: cycles = 4 R C, in milliseconds.
Why is it 4?
Kevin.

Jon Williams
08-15-2005, 10:52 AM
When I went to tech school I was taught 5 TCs (time constants) are required to charge (or discharge a capacitor). During each TC, the cap charages to 63% of the available span (between where it is and where it's going). For five volts, for example:

0: 0.00
1: 3.15
2: 4.32
3: 4.75
4: 4.91
5: 4.97 <-- considered full charge at 5 TC

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Jon Williams
Applications Engineer, Parallax

KenM
08-15-2005, 12:32 PM
For what it is worth, I was taught the same 5 TC's in school.

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Ken