another dumb question, but should be easy for you lot :)

[Gabrielle]

Can you please tell me the symbols for capacitors, example what symbol is for microfarad, Picofarad etc.etc. pretty please.. got a bunch of capacitors, and can't work out which one to use

But still learning ;-)

 

[Nostrafus]

Okay, these are just from memory, I can't remember which one is which

Farad = F (Uncommon, only used in high capacity projects that require am extremely large amount of discharge)
Millifarad = uF, or mF (Can't remember)
Picofarad = pF
Microfarad = mF, or uF (Can't remember)

Those are the only units of measurement I can remember, at least the only ones you can find anyway.

 

[Gabrielle]

mmm it Microfarad i need to use , says enter Microfarad in the calculator to work out the timing... i have a 47uf capcitor just wondering if thats the right one hehe

 

[Nostrafus]

Okay, so you're using this in a timing circuit, well if you still want to keep your chip, I'd say go with something smaller, like .1uF

So what's this for anyway ?

 

[Gabrielle]

in general just playing to learn *smiles* find its easiest way to learn, to actually do it, instead of reading how to do it
hehehe

Basically turn turn a vibrating motor on and off ever second or so

just for trial

 

[Nostrafus]

Okay, hold on a sec... lemme figure something out, just digging out some of my old books and stuff... I am completely wrong with the first post...

 

[Nostrafus]

Okay it's trying to tell me that uF is nanofarads, which doesn't make sense, because if I remember correct the uF marking is to distinguish between Micro and Milli Farads on the capacitor... now my head hurts...

 

[Nostrafus]

Somebody else finish this I'm going to go eat and forget that this just happened...

 

[Gabrielle]

im trying to make this you see **broken link removed** the LM555 - ASTABLE OSCILLATOR CALCULATOR
on the page, just trying to work out what capacitors i have, have 1,600 resistors hehe bought a pack, but only have limited types of capacitors

 

[Gabrielle]

Awww hehe okies thanks anyway

 

[Nostrafus]

Okay, so yours would be .047 microfarads... here's a conversion chart: **broken link removed**

 

[Nostrafus]

But if you run in this mode you're not finding the duration of time between you're finding the duration of time the pulse lasts.

 

[seeker]

Hi Gabrielle,

Most of the time capacitance is referenced to microfarads (uF)
1 microfarad =1 millionth of a farad = 1 uF = .000001 Farad
Then you have your nanofarads and picofarads too.
So when a circuit calls for .01 cap. it usually means .01 microfarad. (.00000001 uF)
Hope it helps a little

 

[Skapone]

Thought I might just give you some info about prefixes of units. Sorry if this confuses any not so mathematically minded people.
I have use the ^ notation to indicate indices so 10^2 is 10 squared and 10^-3 is 10 to the power of -3.

Pico (p)
10^-12
0.000000000001

Nano (n)
10^-9
0.000000001

Micro (u)*
10^-6
0.000001

Milli (m)
10^-3
0.001

Centri (c)
10^-2
0.01

Deci
10^-1
0.1

Deka
10^1
10

Hekto
10^2
100

Kilo (k)
10^3
1 000

Myriad
10^4
10 000

Mega (M)
10^6
100 000

Giga (G)
10^9
100 000 000

Tera (T)
10^13
100 000 000 000

*actually a u with long leading tail but can't get it to work on the forum. It is the lower case Greek letter Mu, which is the Greek equivalent of the English letter M.

to use the table just multiply your value by the corresponding multiplier to get it to non-scaled units.

So if you have a 20nF capacitor you also have a 0.00000002F or a 20x10^-9F capacitor (you can see why they use the short hand). Or if you have a 80mH inductor you also have a 80x10^-3H or a 0.08H inductor.

Most scientific calculators should also have a button called EXP or E or EE which makes this converting a whole lot easier.

Engineers almost always use indices to the power of 3 ie. milli, micro, mega, giga

Please correct me if I got anything wrong.

P.S. I did have a nice table but the forum didn't alow for anymore then 1 space between letters

 

[Nostrafus]

µ I got it to work

 

[Skapone]

Mu

thats the one