Question about resistors

TomGeorge:
Hi,

if that array let's say can hold up to 13 resistors (13 pins)

Sorry, it depends on what you want, resistors have 2 connections, an array of 13 resistors will have 26 pins , or if one end of the resistors is connected together then it will be 14pins.

We can see what you are trying to do, and the resistor networks are designed with this sort of job in mind.

I suggest you go to E14, farnell, RS or digikey online and use their search facility to look at their stock.
What you will probably find arrays of 4 or 6 resistor with all their connections on pins, to 4 to 13 resistor arrays with a common connection pin.

Tom....... :slight_smile:

oww ok so lets say an array that contains 5 resistors, it will have 10 pins ?! if that is the case then it's solved and better than the common one !

Grumpy_Mike:

but usually the resistor is connected to the anode + of the LED from where the current comes to resist the number of current

No that is wrong and shows a total lack of understanding about electricity.
It makes no difference which direction current flows. Beginners think that a resistor "uses up" electricity first before it gets to the LED. This is just rubbish.

Current flows through all parts of a series circuit.

so the resistor can be connected in any way and still have the same job, resisting the current that comes to "protect" the LED from not burning ? (talking about LED here)

so the resistor can be connected in any way and still have the same job, resisting the current that comes to "protect" the LED from not burning ? (talking about LED here)

Yes.

lets say an array that contains 5 resistors, it will have 10 pins

That is only one configuration. Did you download the data sheet from that link. It showed that there were three ways to configure the resistors. If there is a common point like you want, you can get 13 resistors in a 14 pin package. Read that data sheet.

firashelou:
so the resistor can be connected in any way and still have the same job, resisting the current that comes to "protect" the LED from not burning ? (talking about LED here)

Check my photos in replies 7, 8 and 9 here.

Grumpy_Mike:

so the resistor can be connected in any way and still have the same job, resisting the current that comes to "protect" the LED from not burning ? (talking about LED here)

Yes.

lets say an array that contains 5 resistors, it will have 10 pins

That is only one configuration. Did you download the data sheet from that link. It showed that there were three ways to configure the resistors. If there is a common point like you want, you can get 13 resistors in a 14 pin package. Read that data sheet.

yes i didn't noticed at first the diagrams, but now i see so there is 3 ways, the isolated (the one i personally need), the common (which can be used for pull up or down push buttons which i will need too) and the dual resistors, so what is the dual resistors used for ? parallel resistors ?

the isolated (the one i personally need),

Not for the LEDs you don't. The LEDs have a common connection either +5V or ground. You need the common connector array for LEDs.

i am now like i never worked with electronics before ! this is really confusing ! i don't understand we always say the conventional direction is from + to - and then we put a resistor before a LED connected to +, and now u say doesnt matter it can be put behind ! then there is no actual direction for the current ?! and how the resistor still works ?! if current goes threw resistor and becomes limited to get the right value needed for the LED, then it should be placed before, if we placed it on the - , it's like the current goes to the LED (burn it down) and then goes to the resistor and comes back to the source ! so the resistor is useless in this, comment please !

i am now like i never worked with electronics before

Yes it sounds like you have never worked with electronics before if you think this is how it works.

and now u say doesnt matter it can be put behind !

Yes you can.

if current goes threw resistor and becomes limited to get the right value needed for the LED, then it should be placed before, if we placed it on the - ,

NO!!!!
The current does not get reduced from one component, it is the whole circuit that matters. In a series circuit the current is determined by the impedance of all the elements of the circuit added together.
Imagine a circuit with two resistors in it, a 500R and a 1K. No matter what way round you have the resistors if you apply 5V to them there will ALLAYS be 3.3mA flowing through each resistor. Swap the order of the resistors and the result is exactly the same, the same current flows. The direction of current travel is unimportant.

it's like the current goes to the LED (burn it down) and then goes to the resistor and comes back to the source ! so the resistor is useless in this

NO!! The resistor in in the circuit limiting the current. You have to look at the circuit as a whole not just one bit of it otherwise you come up with misconceptions like you have.

Grumpy_Mike:

it's like the current goes to the LED (burn it down) and then goes to the resistor and comes back to the source ! so the resistor is useless in this

NO!! The resistor in in the circuit limiting the current. You have to look at the circuit as a whole not just one bit of it otherwise you come up with misconceptions like you have.

well i am officially confused !

so let's see, the resistor is in a circuit to reduce the whole current ?!

well if not what i said before then why use a resistor if it's not there to let the current be limited to get threw the LED without getting burned :S ?!

well i am officially confused !

so let's see, the resistor is in a circuit to reduce the whole current ?!

So you have a water hose. Does it matter if the flow control valve is at the start or end of the hose? Does the valve control the water flow through the hose no matter where it's located?

Think of like two pieces of hose connected to a faucet. One piece of hose is the resistor and the other is the LED. The LED hose is marked with a + on one end and a - on the other. The faucet is like the + side of a battery or voltage source. It doesn't matter which hose you connect to the faucet first. The same amount of water (current) will flow through both the resistor hose and the LED hose. The LED hose just won't light up unless the + end is closest to the faucet.

Make any sense?

retrolefty:

well i am officially confused !

so let's see, the resistor is in a circuit to reduce the whole current ?!

So you have a water hose. Does it matter if the flow control valve is at the start or end of the hose? Does the valve control the water flow through the hose no matter where it's located?

there is still something missing here, we have the battery 5v which will generate the current needed by the components let say we have a LED 3V, so the resistor will create a voltage drop to protect the LED from burning under 5V right ?

I should have added that the LED hose has a check valve in it that will only allow water to flow from the + end to the - end.

firashelou:
so the resistor will create a voltage drop to protect the LED from burning under 5V right ?

When forward biased the LED (or any diode) has a characteristic voltage drop across it; whatever is not across the diode is across the resistor. So, it's that remnant (Vsupply - Vdiode) across the resistor that determines the current.

Though electron flow goes from negative to positive, hole flow ("conventional flow") goes from positive to negative.
So, current is everywhere at once.
Sleep well.

i didn't understood what you mean ?

well in that case there is no such a thing as direction for the current the + to - is totally wrong isn't it !?

firashelou:
well in that case there is no such a thing as direction for the current the + to - is totally wrong isn't it !?

No, current in a DC circuit still has a polarity.

The "flow" thing is a contrivance, the holes go one way and the electrons go the other, but they don't crash in the middle of a circuit.