Newbie Questions

[Sanghera]

Hi,
I was looking on the digikey website for some of the parts for the picstep controllers. I see so many options for just resistors. What is the difference between Metal Film, Ceramic, Carbon Resistors, does it matter which one I use? Also, for Capacitors, does it matter wheather electolytic or MKT? I'm just not sure weather choosing one or the other would alter the results. Do you guys have any good sources on electronic components that would help me?
Thanks.

[Al_The_Man]

The Carbon style are the older type and I try to stay away from them, especially if they carry the rated current, they tend to change value with age/heat, the Metal film are one of the most common,especially in the small wattage range, they are stable and generally smaller than their carbon counterpart, with capacitors, anything 1µfd and up is generally either electrolytic or (much smaller) tantalum, these are generally used where pure DC or low frequency ripple is present. They cannot be used on high frequency or pure AC, one reason is they posses inductance and leakage on AC.
For large values on AC a high quality AC low loss (non-electrolytic) type capacitor should be used, for small values you can use MKT or MKP which has extremely low losses due to polypropylene dielectric.
Al

[Sanghera]

So MKT capacitor is an AC cap? Also, so it really doesn't matter which resistor you use, as long as it is the right resistance?
Thanks.

[Al_The_Man]

Just about all capacitors can be used on DC it is when they are used on AC the type can become critical.
Resistors not critical except when again dealing with very high frequencies, you can do without ones that introduce inductance the same as a capacitor could.
you also have to use the appropriate wattage.
Al

[smarbaga]

resistors, capacitors, transistors, inductors, internistors, thermistors, diacs etc, etc....
there are libraries on each subject where to use them and why/why not .....
if a person is going to build an electronic device he/she must know about the components that is going into it before it will work reliabily...
just search on the net about one component at a time and grasp what u can....
we must crawl before we can fly ..... and when u have that component figured out a new and improved one will be invented so you will never be boared.
also reading about other peoples designs will help alot.
but i see bits of advice placed on here that i know is not carved in stone ....
so just be aware and keep the fire extingisher handy, after blowing a few walls out, i do... lol
ps : electricity is the silent killer ........ always keep that in mind ... and you will be ok ... if u don't try it ... you'll never know...