# Which is better parallel or series wiring

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verifier - 06.08.17 18:23

Hello,

I'm not quite as fit when it comes to electrics, so a question:

I have 12 LED lights. In addition, it has its own circuit. Then star or / and series cabling. Is it enough to install a resistor within the circuit or do I have to install a resistor in front of each LED?

Where do I have to install the resistor? No matter which wire from the lamp or which line of the circuit?

Manfred

# 1 | Multiple LEDs - One Circuit - One Resistor?

Sunshine2014 - 06.08.17 19:00

Hello Manfred,

Well, I'm not an expert, but I have already installed a lot of LEDs on my system. Resistance is absolutely essential with LED, where you install it in the circuit does not matter as far as I know. But I rather see the concern that you want to put 12x LEDs in series, with 12V voltage that's rather stupid.
But it depends on the voltage of the individual LEDs (e.g. on the light color), I never install more than 6 in a row at 12V.

Kind regards
Rene

# 2 | Multiple LEDs - One Circuit - One Resistor?

BR65 - 06.08.17 19:04

Hello Manfred,

##### Quote - Answer No .: | Surname:

Star or / and series cabling

Star cabling (connection) is a wrong expression here, it is used with three-phase current.

##### Quote - Answer No .: | Surname:

I have 12 LED lights

Without knowing exactly what these "lights" are, an indication of whether a series connection or a parallel connection is to be used cannot be clearly stated.

If it is a matter of simple LEDs (depending on type and color 2 - 3 V voltage), it also depends on what kind of supply voltage you have.
In general, however, when connected in series, 1 resistor per row is sufficient, and when connected in parallel, 1 resistor for each LED.
Which side (connection) of the LED you connect it does not matter, as well as the way around that connects it.

Greetings Detlef

# 3 | Multiple LEDs - One Circuit - One Resistor?

msfrog - 06.08.17 19:50

Hello Manfred,
with series connection: 1 resistor is sufficient. But pay attention to the voltage, if you switch too many LEDs in a row, nothing lights up anymore.

When connected in parallel, each LED should have its own resistor. It * may * work to use only one, but if the LEDs deviate too much from each other, only those that need the least voltage light up, the others remain dark. Since resistors cost practically nothing, you should refrain from such experiments and get it right right away.

Best wishes
Carsten

# 4 | Multiple LEDs - One Circuit - One Resistor?

verifier - 06.08.17 20:34

Hello,

Thank you for your answers. I will do a parallel connection. The LED operating voltage is 3 V, the supply voltage 12 V, I use a 450 Ohm resistor for each LED.

Have a nice evening

Manfred

# 5 | Multiple LEDs - One Circuit - One Resistor?

cow56 - 06.08.17 20:49

In my control panel, each LED (approx. 160 built in) has its own resistor.
The resistances were chosen to be much larger than calculated, since the LEDs otherwise shine too brightly.
That's why I recommend trying out which resistance is right for you beforehand.

Greeting

huk

http://www.modellbau-huk.ch/eisenbahnmodellbau/...lagenbau/index.html#

Post edited on 08/07/2017 21:41.

# 6 | Multiple LEDs - One Circuit - One Resistor?

msfrog - 06.08.17 21:14

Hello Manfred,
I would also rather use 1 - 2 kOhm. Firstly, you don't want floodlights, secondly, the LEDs last longer.

Best wishes
Carsten

# 7 | Multiple LEDs - One Circuit - One Resistor?

brawafan - 06.08.17 21:23

Hello,
if that's 3mm LED, it should be 20mA. Then around 1 kOhm at 12 V is okay, we have installed 1.2-1.6 at 16 V.
450 ohms are too little for 20 mA, they should even smoke immediately, otherwise floodlights.
VG
horst

# 8 | Multiple LEDs - One Circuit - One Resistor?

Zwengelmann - 06.08.17 22:05

Hello,

"too little", "floodlight", ...

R = (supply voltage - n x 3V) / I

I is the desired current, which should be significantly lower than the maximum current according to the data sheet.
n is the number of LEDs in series.
I assume that the supply voltage is smoothed. E.g. from a plug-in power supply.

E.g. 12V supply voltage, 3 LEDs in series, desired current 5mA -> I = 3V / 5mA = 600 Ohm. Standard values ​​are 560 ohms and 680 ohms. To be on the safe side, always use the larger one, i.e. 680 Ohm.

With your 12 LEDs you create 4 groups of 3 LEDs and give each group a series resistor. Get a whole sack of resistors. Two in series, half current, not quite as bright. 2 in parallel: double current, brighter.
I do not recommend a resistor assortment box, there are too many resistors in it that you will not be able to use. But with the values ​​mentioned you can get quite a long way with parallel / series connection.

If you take a series resistor for each LED, that is approx. 1800 ohms at 5mA and 12V. However, I would rather form groups, it takes less effort. 1800 ohms is a standard value.

Attention: Old-fashioned green / red / yellow single-color LEDs have a lower operating voltage. Red e.g. approx. 1.6V, details see data sheet.

greetings
Zwengelmann

# 9 | Multiple LEDs - One Circuit - One Resistor?

Markus L - 07.08.17 08:19

In any case, a separate resistor for each LED!

When calculating the LED series resistor, the desired LED current intensity is included in the denominator.
If you have several LEDs in parallel, you would have to add them up to a total value.

The series resistance then becomes smaller.

If a single LED should fail (or it no longer has any contact), the voltage ratios within your circuit change, i.e. the increased total current would find its way through the now lower number of LEDs and, in the worst case, let them burn out.

Therefore: always a separate series resistor for each LED.

Greeting,
Markus

# 10 | Multiple LEDs - One Circuit - One Resistor?

Chairo - 07.08.17 08:39

Hello everybody,

you can do it a little differently here. The available voltage is 12 V. This is sufficient to operate 3 LEDs (no matter which color) safely.
So if you need 12 LEDs, you connect 4 x 3 LEDs in series and each row has a resistor that is calculated according to Zwengelmann's formula (# 8).
It will look like that:

-------------- 12 V -------------
LED LED LED LED
LED LED LED LED
LED LED LED LED
R R R R
---- common ground ----

Greetings,
Dietmar

# 11 | Multiple LEDs - One Circuit - One Resistor?

Der_Didi - 07.08.17 09:13

##### Quote - Answer No .: 7 | Name: brawafan

if that's 3mm LED, it should be 20mA.

Hello Horst,

what exactly do you mean by "should have":
Can be supplied with this amperage during operation, or
can this amperage as the maximum permissible value?
##### Quote

450 ohms are too little for 20 mA, they should even smoke immediately, otherwise floodlights.

At 12 V and 20 mA, however, these 450 ohms would come out for the series resistor, so nothing to "smoke".
(It has already been written that operating LEDs with the permissible current strength is neither necessary nor a good idea ... )

LG
Didi

# 12 | Multiple LEDs - One Circuit - One Resistor?

Arnold_Huebsch - 07.08.17 09:51

Folks!
The series resistance calculation has led to absurdity. There are LEDs that shine extremely brightly at 500uA, others do not achieve this brightness even at 20mA.

Therefore, estimate a rough value, try 500Ohm to 10k series resistor and then decide which series resistor you need. Without knowing the electrical parameters of the LED, every recommendation or reading around is pure coffee brew.
-AH-

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