Breadboard power rail capacitor

Thread Starter

robijnix

Joined Feb 23, 2013
7
Hello,

I see a lot of people have capacitors over the power rails of their breadboards, and i don't really understand why?

Thanks
 

thatoneguy

Joined Feb 19, 2009
6,359
See my sigline on bypass caps.

I usually put a 22uF on each side if they are connected, then a 0.1uF ceramic between + and - roughly every 15 spaces, and again next to the ICs.

The rails alone will make things work mostly, but you need them close to the IC supply if you are doing ADC conversions.
 

Thread Starter

robijnix

Joined Feb 23, 2013
7
woh that was exactly the info i was looking for, thanks a lot.

so if i understand this correctly, this is only really necessary if you want your voltages really precise?


edit: and also, they become more important with higher frequentie, and large circuits?
 

ErnieM

Joined Apr 24, 2011
8,377
woh that was exactly the info i was looking for, thanks a lot.

so if i understand this correctly, this is only really necessary if you want your voltages really precise?


edit: and also, they become more important with higher frequentie, and large circuits?
Large or small a bypass cap will help keep noise out of the power supply lines so it doesn't move from one area of your circuit to another.

For the time being just assume you need them and put them in... even professionals do that, and (sometimes) go back later and take some out.
 

crutschow

Joined Mar 14, 2008
34,280
..............................
so if i understand this correctly, this is only really necessary if you want your voltages really precise?

edit: and also, they become more important with higher frequentie, and large circuits?
The capacitors aren't just needed for precise voltage, they are to prevent spikes on the power line, due to the switching currents of one digital circuit, causing false triggering of another circuit. And even though the circuit may seem to work OK without them, under different conditions (temperature, supply voltage), the spikes could start to cause problems (which can be a bear to troubleshoot). So always use the recommended bypass capacitors in your circuit..

It really has little to do with circuit size or operating frequency. The spikes are generated when the circuit switches (changes state) and the magnitude of the spike is independent of the switching frequency.
 
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