Question about inline resistors.

[william]

Why would somone use a series of resistors connected end to end without anything connected inbetween them?  I'm looking at an effect, and there are a couple of resistors connected inline and it has me confused.  Wouldn't just one resistor with the sum of them work the same?

William

[travissk]

Probably - what values are they? Perhaps it was easier to come by two smaller values.

[Rob Strand]

It's either to obtain a specific value, or, simply to avoid using wire links (believe it or not).

[william]

There are 10 330k and one 220k.  So yea, I guess it could be to achive an uncommon value.  What did you mean by Wire links Rob?  

On a similar note, when wireing multiple led's to the same power supply, can they all share the same resistor, or should they each have their own?

William

[Mike Burgundy]

you can use one resistor for multiple LEDs, but it will have to be a lower one: the parallel LEDs combined require the same voltage but more current - the voltage drop across the resistor should be the same.
If you're using two LEDs, use a resistor half as large as you would with one LED to achieve this.

[R.G.]

It can also be to obtain a higher power rating with the available resistors.

you can use one resistor for multiple LEDs, but it will have to be a lower one: the parallel LEDs combined require the same voltage but more current

Note that this only works well if you have identical LEDs. LEDs vary quite a bit in forward voltage, so if you use mismatched ones, the lowest voltage LED will hog all the current.

[Paul Perry (Frostwave)]

If you only have 2 leds, then there is usually enough volts to run them in series, via a single resistor. No problem wiht one hogging the current then.

[Rob Strand]

What did you mean by Wire links Rob?

Have you seen PCBs with wires put on the component side of the board?  Just thin silver wires soldered in like components.  They act like wire to connect two tracks, this is usually done when you can't fix the tracks on the PCB.  

Instead of having a resistor then one of those wires in series some board are made with two resistors in series and no wire.