Powering LEDs Question

[SparkyCal]

Below is a picture of a circuit I am building on a PCB board. I could not figure out how to make the picture bigger, so if it is difficult to see, you can see it full size at. :32 here:

You will note that the schematic calls for a number of individual 560R resistors that are attached to pin 3 of the 555 timer, and then attached to a LED ( one LED per resistor).

I am looking for advice on how to physically wire/solder this.

Do I solder one wire to Pin 3, and then attach one side of each resistor to that wire? I am thinking that could be quite messy because then I would have 12 resistor ends, all connecting to that single wire coming from Pin 3 of the 555 Timer.

I am sure there must be a better way, but I've never done this before. I know that the circuit boards I bought came with break off header pins. Will those help?

Thank-you

 

[ramussons]

Do I solder one wire to Pin 3, and then attach one side of each resistor to that wire? I am thinking that could be quite messy because then I would have 12 resistor ends, all connecting to that single wire coming from Pin 3 of the 555 Timer.

Yes, that is how it is done, even is it is a PCB. Or do you feel that connecting 12 resistors to a single pin is easier? And please notice that the "gnd" has more than 12 connections.
The LED's with their Resistors are strung exactly like in the schematic, though their physical layout may be shaped like the heart.

 

[bertus]

Hello,

The circuit will draw a current of 12 X ledcurrent.
When using 6 X 2 leds in series , the used current can be half, and prolong the battery life.

Here is a larger picture of the schematic from that video:



Click on the picture to show it even larger.

Bertus

 

[Bluejets]

Even could go 2 legs in parallel, 6 leds in series and a 100R resistor in each of the two legs.

Original circuit would exceed the current rating (200mA) of the 555 (216mA)

 

[bertus]

Hello,

@Bluejets , It is not wise to put several leds direct parallel:



https://electronics.stackexchange.com/questions/174584/is-it-ok-to-put-leds-in-parallel

And an other page with the why:
http://lednique.com/parallel-leds/

Bertus

 

[Harald Kapp]

It is not wise to put several leds direct parallel:

The suggestion is not to have all LEDs in parallel, rather build 2 strings of 6 LEDs in series, each string with 1 resistor, both strings in parallel:

Perfectly legitimate and saves power: power is used to illuminate the LEDs, not to heat the resistors.

 

[bertus]

The suggestion is not to have all LEDs in parallel, rather build 2 strings of 6 LEDs in series, each string with 1 resistor, both strings in parallel:

That will likely not work, as the output voltage of the 555 will be to low.
The output voltage is about 2 volts lower as the supply voltage.
The original circuit uses a current of about 15 mA for each led.
Perhaps make 3 strings of 4 leds with a resistor of 120 Ohms in each string, wich will result in about 17 mA in each string.

Bertus

 

[SparkyCal]

I think I will stick to the original schematic, only because I don't see hsving to leave this circuit on for a lomng period of tiem, thus i am not overly concerned about battery drain.

I have a question though. If in the diagram, I decided to twist together all the resistor leads, and then connect the twisted together end, to Pin 3, woukd this screw everything up. It is necessary that each resistor travel to the Pin3 lead on its own? I am thinking it would screw everything up because it may change the value of the resistors to be the addition of all the resistances. True?

 

[Harald Kapp]

It is necessary that each resistor travel to the Pin3 lead on its own?

No, definitely not. In this circuit it makes no difference. The resistance of the wire connecting the resistors to pin 3 is negligible compared to the resistances used (unless you use ultra-thin wire ).

Just for future reference: There are circumstances where it matters how you make the connection. Ususally when very high frequencies or very steep signal edges are involved. This is off no concern here.

 

[SparkyCal]

I was not concerned about the wire. I was wondering. If the resistors were bunched into one connecting point, could they form a super resistor or will they all maintain their same resistance values

 

[bertus]

Hello,

Looking at the back of the PCB in the video, each resistor is connected to one led:



Bertus

 

[Harald Kapp]

I was wondering. If the resistors were bunched into one connecting point, could they form a super resistor or will they all maintain their same resistance values

Why would the resistance of a component change depending on how it is connected?

In this example each resistor has an (arbitrary) resistance "R", regardless of the connection.



A different story is a connection like this one:

Here the 3 resistors are connected on both ends, a parallel connection. While each single resistor still has a resistance of "R" (remember it doesn't change with the type of connection), the total circuit with 3 resistors in parallel has a resistance of 1/3 × R.

Whereas in this connection

The total of the resistance is 3 × R.

Read more about series and parallel connection of resistors e.g. here.