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Topic: capacitor in 595 tutorial (Read 995 times) previous topic - next topic

serik

Hej,

I have only a very small knowlege about electronics and want to use some 595s parallel.

The tutorial about this topicis is really nice (http://www.arduino.cc/en/Tutorial/ShiftOut) but the capacitor in the tutorial has in the text a value of 0.1µf and in the image a value of 1µf. Since I do not really understand capictors and am not able to calculate the right value my question is: What is the right value (or are they maybe both usable)?

fdufnews

In my opinion this capacitor is of no use if there is no error in your sketch.
It is a good practice to keep ST_CP at the LOW level when not needed and pulse it (HIGH immediately followed by LOW) when you want to transfer the data from the shift register to the output one. In that case there is no reason for a capacitor on that pin.

MikMo

It's a decoupling capacitor, and it should be 0.1uF.

It's common practice to use such a capacitor acros the powersupply pinns on all digital IC's.

http://en.wikipedia.org/wiki/Decoupling_capacitor

retrolefty

No it does not appear to be a simpe power decoupling capacitor. It is hooked to the latching signal and appears to be there to slow down the signal timing a little.

From the text: "Notice the 0.1[ch65533]f capacitor on the latchPin, if you have some flicker when the latch pin pulses you can use a capacitor to even it out. "

I would go with .1 as the text says as 1mfd is quite a bit to hang on a logic signal.

Lefty

serik

Thank you for your answers. I will go with the 0,1 capacitor but if the 1 is wrong in the image shouldnt it be corrected (well, not from me cause i have too less clue)? Anyway from the little I understand from the wikipedia article I could imagine that the described use is the same as the one of an decoupling cpacitor ... reducing noise and therefore less flicker.

MikMo

Arrgh.
I should have read the text before answering - sorry

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