Confused about resistors

[MKnight]

Right im confused about W and Ohms i need a 4,7w 4.7ohms resistor but i cant find one i look on the store but they are all over rater like 5W

like the 4.7ohm 10w resistor do i use this or does it have to be 4.7W or does the W not matter as im just intrested in the Ohms value...?

This is doing my head in as nothing i find helps only adds to the confusion...!

can you clarify..?

i need a 1W, 1.2 resistor & 4.7 Watt or 4.7 ohm...

[Silver Serpent]

Wattage is a minimum. You can always use a higher wattage rating resistor, and it will not affect brightness. Don't go overboard, since the higher wattage resistors are physically larger and take up more precious space in your saber. If you need a 4.7w resistor, either a 5w or a 10w will work, though the 10w will take up more room.

[MKnight]

Thats what i thought as the higher watts just deal with more current but the same resistance right..?

[Silver Serpent]

Simple answer: Yes, higher wattage supports more current. Resistance is Ohms.

Longer answer: Wattage deals with more *power*. Power = Voltage * Current. An increase in current (with voltage remaining same) will require more wattage.

[Kevin Starwaster]

Wattage is a minimum. You can always use a higher wattage rating resistor, and it will not affect brightness. Don't go overboard, since the higher wattage resistors are physically larger and take up more precious space in your saber. If you need a 4.7w resistor, either a 5w or a 10w will work, though the 10w will take up more room.

Yeah, those are so big, instead of mounting the resistor on a PEX, you're sort of mounting the PEX on the resistor. Hmmm. Sounds like there's a Soviet Russia joke in there somewhere...

[MKnight]

Yeah, those are so big, instead of mounting the resistor on a PEX, you're sort of mounting the PEX on the resistor. Hmmm. Sounds like there's a Soviet Russia joke in there somewhere...

LOL... funny :-D

[MKnight]

So why are all the resistors in 100k 150k etc when im looking for a 4.7ohm resistor?

and the multimeters im looking at is showing:

Resistance 200Ω - 2000MΩ ± (2.5 % +3)

[Silver Serpent]

http://www.thecustomsabershop.com/47ohm-5w-resistor-P492.aspx

Different resistors for different purposes. Try the calculations for an accent LED with a Li-Ion pack, and you'll quickly see why you need higher ohm resistors.

[MKnight]

http://www.thecustomsabershop.com/47ohm-5w-resistor-P492.aspx

Different resistors for different purposes. Try the calculations for an accent LED with a Li-Ion pack, and you'll quickly see why you need higher ohm resistors.

I get that i dont understand where 4.7 ohm corrolates to 00??K do you see what im asking..?

[Forgetful Jedi Knight]

I get that i dont understand where 4.7 ohm corrolates to 00??K do you see what im asking..?

Depending on your multimeter, there may either be a lower setting, or the reading may be displayed as .004 or something like that.

[MKnight]

Depending on your multimeter, there may either be a lower setting, or the reading may be displayed as .004 or something like that.

Im still none the wiser... is there some kind of chart that i can work all this out as resistors here in the uk all seem to be:

SMD 0805 Resistor 0-1k Ω
SMD 0805 Resistor 1k-100k Ω
SMD 0805 Resistor 100k-350k Ω so where do i work my my ohms value from that..???

im looking here to buy resistors...!

http://stores.ebay.co.uk/h-m-comp/Resistors-Carbon-Film-/_i.html?_fsub=1554243016

[Silver Serpent]

Well, 0-1k Ω means 0-1000 ohm. The "k" is kilo (1000) and "Ω" is the symbol for "ohm". 1k-100k would be 1,000-100,000. Or maybe 1.000-100.000, I'm not sure which you use in the UK.

It's listing a range. The 4.7 ohm resistor you're hunting for will be in the 0-1k range.

That being said, SMD resistors are really small. I hope you have experience soldering them. It's pretty tricky if you haven't done it before.

[MKnight]

ok i think im with you now :-D so is 4.7 ohm 4.700K? or am i way out..?

Yea i used to chip DVD players, and those legs where bloody small (and close) so i can solder on those little resistors.

[Silver Serpent]

In the UK, do you write One Thousand as 1.000 or 1,000? In the US we use a comma to separate our thousands (1,000 = one thousand) and we use a decimal to represent numbers less than one (4.7 = 4 and 7 tenths)

You want a resistor that is 4 and 7 tenths ohms. K is kilo. I know you are familiar with the metric system over there. kilo = thousand. 4.7k is 4700.

Any resistor with a k in it is gonna be far more resistance than you need.

[MKnight]

Ok i think i get you, metric is a pain in the arse..... :confused:

this was interesting: http://www.1728.org/resisclr.htm

[Forgetful Jedi Knight]

Are you specifically looking for SMD resistors? Try newark.com they have a UK site, a little search-fu and you should find what you need. ;)

[Silver Serpent]

Metric is easy. Everything is base 10. US units are a pain :)

That page is pretty good for explaining the units, though you're not going to see color bands on your SMD resistors. Pray you never dump out a bunch of different valued SMDs and have to figure out which is which. I *think* they're labeled, not sure.

[MKnight]

Its ok i just was searching for the wrong shizzle, seems all the resistors are well over value and its better to get a couple of hundread of them from 1ohm, to 9.1ohm so im fixed :-D

Nightmare.. sorry for the dumb arse comments...please feel free to turn down your sabers and swipe away..

[Silver Serpent]

No worries. I keep a variety pack of resistors on hand for saber issues. Mostly stuff like when I change my mind about power supplies and/or blade color. It's good practice to have extras around in assorted values.

[MKnight]

Metric is easy. Everything is base 10. US units are a pain :)

That page is pretty good for explaining the units, though you're not going to see color bands on your SMD resistors. Pray you never dump out a bunch of different valued SMDs and have to figure out which is which. I *think* they're labeled, not sure.

LOL im going to use the smds on the PC2 :-) that would be a nightmare fair play..!

Yea i got confused with trying to convert US to UK and got lost when they dont need converting (as i can tell)

*slaps self with large fish*

[MKnight]

ok i figure i need the following running at 7.4 volts

4.7 Ohm FOC white.

220 Ohm PWR led white.

1 Ohm red luxeon star (off 1000mA 3.0v driving the blues).


============================
Red Main led (luxeon Star)
============================
Source voltage 3.0
Diode forward voltage 2.5
Diode forward current (mA)700 mA
=1/4 Watt or 1 ohm resistor?
============================

============================
White FOC led (luxeon Star)
============================
Source voltage 7.4
Diode forward voltage 3.25
Diode forward current (mA)1000 mA
= 4.7 Watt or 4.7 ohm resistor?
============================


============================
Power LED
============================
Source voltage 7.4
Diode forward voltage 2.2
Diode forward current (mA)25 mA
= 1/4 Watt or 220 ohm resistor?
============================

Phew what a nightmare....