resistor question

[rsd]

i was about to order my leds and resistors but the shop i am ordering from does not carry resistors upto the ohm rating i need. is it possible to solder a few 100 ohm resistors in series and get the same effect of a 300 ohm resistor?

[ammerzoden]

serial Rt= r1+r2+r3
parallel 1/Rt= 1/r1 + 1/r2..

so three times 100ohm in serial is 300 ohm :cool:

[rsd]

thanks for the info :D

[Maximilianop]

Of course, serial Rt= r1+r2+r3, is theorical, in practice you suffer a very little loss becuase of the soldering, legs length, etc.

I would tell you to get a 5 or 10 Ohms extra resistor, just in case

[rsd]

so for 300 i should go 100+100+100+5?

[Maximilianop]

so for 300 i should go 100+100+100+5?

For 300 you should go with 300, even if it means to walk 10 more blocks to reach a descent shack.
Anyways, if your lazy, I should say buy 3x 100, and 1x 5, 1 x 10.
Then solder the 3x 100 together and read with a multimeter, if less than 299 Ohms, add the 5 Ohms one.

[nukleuzdj]

i doubt that 1 ohm would really make that much differance

[julspower]

hey
just dont bother with that???
a 250ohm resistance would light a del anyway
it wont make any del explose to run it a 30 ma....

it will die before but what even at half live it still give you 5000 hour of fun
go for 3 100 ohm then just solder them