I wonder if it is useful to use a capacitator to compensate small powerdips in the electricity network. I was thinking to a condensator of 1000 uF or more. Is that a useful thing to do? If so what is a good capacitity (9v for the Arduino).
Yes, for DC that is done all the time.
Using a 1000 microfarad capacitor in parallel with a 100nf ceramics capacitor is hardly ever a mistake.
It just depends on how your load is changing.
A 100nf capacitor will compensate high frequency changes. The 1000 µF capacitor will compensate for larger current changes.
Actually everything depends on your power source and what your circuit is doing.
I built a signal generator lately using a switched power supply. And my sinewave output looked terrible on the oscilloscope. Coils and capacitors did not help. So I went back to the old solution.
Transformer, rectifyig bridge, 1000µF and 100nF at the input side, a LM317 voltage regulator, a 1000µF (oversized on the output side) and another 100nF capacitor on the output side.
Now the signals are as clear as spring water.
Or in other words:
There is no golden answer that always fits. However, usually capacitors will not introduce any negative effects. Just keep in mind, that large capacities are like a short circuit in the moment when things are powered on.
You should NOT have larger capacitors on the output side of a voltage regulator than on the input side. In that case you would need a flyback diode to protect your voltage regulator.
arduinoaleman
Sometimes a simple 10 uF Tantalum cap from Vcc to gnd has resolved for me transmission issues (I2C) when small coil relays are switching around. The key is to locate the cap as close as possible to the affected interface power supply.
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i have seen professional boards where every chip had its own 100nf capcitor.
so when it comes to frequencies above 10KHz this CAN make sense.
the most important thing is to understand that the capacitors have to be close to the chips and transistors.
when i built my frequency counter preamplifier (circuit diagram can be found in the Arduino forum),
i found out, that 100nf capacitors can be very important.
without them high frequency signals were very distorted.
so better use too many capacitors than too few.
**arduinoaleman **
Thanks a lot, I go to mount the capacitators.