Smoothing Capacitors

When given guidance to connect a capacitor "across" an input source, and/or using a capacitor to smooth input from a battery (let's say a volatile battery like a car battery), I'm a bit confused on where the connections go.

Do you wire the + from the battery to the + of the capacitor, and the - of the capacitor to the + of your circuit (e.g. Arduino or LED or whatever), OR, do you wire the + of the battery to the + of the capacitor, and the + of the capacitor is also connected (inline) to the + of the circuit, and the - of the capacitor goes to the - of the battery...?

Thanks!

The capacitor goes across the supply, pos to pos and neg to neg.

Weedpharma

Connecting "across" means in parallel.

Additional question: When would I use a capacitor in series?

You can use a cap in series for things like DC offset etc..

You could use a series capacitor to turn something on for a short time. EG, if you put a capacitor in series wth a relay, coil current will only flow until the C charges. When you then take the switched end of the C to gnd, the relay would operate again until the C discharges. If you use a large R, the C can be discharged slowly so the relay will not operate.

There are not many timing operations like this called for with micro controllers!

Weedpharma

weedpharma:
You could use a series capacitor to turn something on for a short time.

Or to block dc while passing ac such as audio or radio frequencies.

Russell.

russellz:
Or to block DC while passing AC such as audio or radio frequencies.

Which is in fact, by far the most common use of series capacitors.