I have thees LED strings in 12V and 5V version. My plan is to make a lot of holes in a wood board and use it as an matrix for the leds.
I have four strings (50 LEDS pr. string) with 12V and two strings with 5V. Total 300 leds. I have an 20Ah 12V Power Supply to feed the leds.
Is it possible to attache the two strings with 5V at the end with a resistor between the 12V and 5V strings? If yes, how big must that resistor be?
these LEDs have quite a big current. So you would need a resistor with a very big pyhsical size that is able to transform all not needed energy into heat. This is a bad idea. You could even start a fire with it.
Any microcontroler can only supply a current between 5mA and 40 mA per IO-pin. much too less for more than two standard LEDs. So you have to use a transistor or a MOS-FET to switch on OFF the LEDs. With this solution you use two powersupplies one with 5V one with 12V to drive the LEDs. Your microcontroller drives the transistors/MOS-FETs.
As you have a 12V 20A Powersupply you need a DC-DC-Step-Down transformer which creates the 5V.
You seem to have only a very small knowledge about electronics. You should be very careful with building this project. It is not dangerous to work with 5V / 12V but you could damage things just out of "not-knowing"
So please start reading about learning electronics and before switching power on on a self build circuit ask back if everything is wired properly.
best regards Stefan
any newbee can apply the most professional habit from the first line of code they write on their own:
add only ONE thing at a time. Test/debug that ONE thing until that ONE thing works reliable - repeat.
The sad thing is: only the REAL professionals write code this way.
StefanL38:
these LEDs have quite a big current. So you would need a resistor with a very big pyhsical size that is able to transform all not needed energy into heat. This is a bad idea. You could even start a fire with it.Any microcontroler can only supply a current between 5mA and 40 mA per IO-pin. much too less for more than two standard LEDs. So you have to use a transistor or a MOS-FET to switch on OFF the LEDs. With this solution you use two powersupplies one with 5V one with 12V to drive the LEDs. Your microcontroller drives the transistors/MOS-FETs.
As you have a 12V 20A Powersupply you need a DC-DC-Step-Down transformer which creates the 5V.
You seem to have only a very small knowledge about electronics. You should be very careful with building this project. It is not dangerous to work with 5V / 12V but you could damage things just out of "not-knowing"
So please start reading about learning electronics and before switching power on on a self build circuit ask back if everything is wired properly.
best regards Stefan
any newbee can apply the most professional habit from the first line of code they write on their own:
add only ONE thing at a time. Test/debug that ONE thing until that ONE thing works reliable - repeat.
The sad thing is: only the REAL professionals write code this way.
I'm not an electro engineer, but i understand more than many thinks. But by asking others and try myself i learning every day. Why do you think i ask instead of just do it? Because i want to do it the right way.
I know what a microcontroller can to and the microcontroller has nothing to do with my question here. I sead i'm going to use an Power supply for this. The microcontroller will only send signals to the leds.
Why do i need mosfets in this case?
Yes, i also know i must step down the voltage from 12v to 5V for not to blow my leds up.
Btw...
It is not a must that i have to add the two strings with 5V at the end. I understand that it maybe is lot of heat going on through an possible resistor between 12V and 5V strings. Maybe it's not possible at all. I just ask, and maybe hope for som simple ideas.
If it's not an simple solution, i just drop the 5V leds at the end. No big deal at all.
i have an Buck Converter that takes 2.5amp. but i think this also will blow up. The possible current for the 5V strings is 6 amps (max). In real life, maybe 1-2 amps. But it's too risky to use it anyway i think.
A resistor would not work to drop the voltage from 12v to 5v, because the voltage drop would vary depending on the current. Three 2.5amp buck converters would work, if you group the 5v strings of LEDs into three groups of 33/33/34 LEDs each. You will want to feed the voltage into the strings at multiple places along the matrix anyway, so supplying three buck converters would not present a problem.
Can you post a link to the 12v string of LEDs, if it actually has 50 LEDs then it sounds like it is driving one RGB LED per WS2811, a bit unusual for 12v where it is common for each WS2811 to control a group of three.
As far as the arduino is concerned, the only load the output pin sees is the data input to the first WS2811, regardless of how many you add afterwards.
david_2018:
A resistor would not work to drop the voltage from 12v to 5v, because the voltage drop would vary depending on the current. Three 2.5amp buck converters would work, if you group the 5v strings of LEDs into three groups of 33/33/34 LEDs each. You will want to feed the voltage into the strings at multiple places along the matrix anyway, so supplying three buck converters would not present a problem.Can you post a link to the 12v string of LEDs, if it actually has 50 LEDs then it sounds like it is driving one RGB LED per WS2811, a bit unusual for 12v where it is common for each WS2811 to control a group of three.
As far as the arduino is concerned, the only load the output pin sees is the data input to the first WS2811, regardless of how many you add afterwards.
No, i'm affraid of that. Resistor is out of the game.
I have three Buck Converters, but i feel it's the "wrong" way to do it. I don't know.. But yes, i could work...
Here is the link. 12V and 5V version of the string is identical in size etc. Some other colors on the wires is the only thing that split dem apart.
It looks like the data signal for both 12 and 5 volt strips can just be 5 volts.
So try, with good possibility of functioning and not much likelihood of damage:
Power the 12 volt strips with 12 volts
Power the 5 volt strips with 5 volts
Feed the signal from the Arduino through a 470 ohm resistor to Din of the first strip
Chain the strips connecting Dout to the next strip Din
Tell us that worked.
[EDIT] looks like I under thought this a bit. Typical. Typing before coffee, never a good idea.
Feed the Arduino signal only to the 5 volt LED strip, not a 12 volt.
When you hook a 12 volt onto a 5 volt, the logic may be ok.
When you hook a 5 volt on to a 12 volt, you may need a simple voltage divider to convert the 12 volt logic signal (if indeed it is) to 5 volts.
AND if you hook a twelve volt onto a 5 volt and the logic isn't OK, then you would need to convert the 5 volt logic signal to 12 volts or whatever 12 volt strips take. Since these are high speed signals, you'd probably want an active level converter that would pull the signal to both extremes (two transistors), not just a follower.
HTH
a7
I think this is more difficult than i first thought, so i think its best to just use my 12v. I have 200 leds in 12v sp i think this is enough 
The WS2811 runs at 5v in the 12v strips, so there should be no problem with the logic levels.
The WS2811 runs at 5v in the 12v strips, so there should be no problem with the logic levels.
This is absolutely correct. You can power 12v strip with a 12v supply and 5v strip with a 5v power supply and all you would need to connect between the strips is Dout -> Din and GND - GND.
I am phrasing it like this simply stating that you have to provide enough 12v power and 5v power.
There may be one little snag, being that the order of the RGB colors might not be the same for both strips.
Working with WS2811 has it's quirks, but as long as you provide sufficient power to the strip (check the requirements eg Watts/meter) and don't make the data line between strips to long, no special tricks are required.
What so you mean with "Dout" and "Din"?
Yikes. Either all responders are in the wrong opera or it’s time for you to hunt down some educational material on smart LEDs.
Connecting Dout from one strip to the Din (data out, data in) of another results in one longer strip. And so forth up to some relatively large number of LEDs on one strip. Hundreds anyways.
It’s what the built on connector jacks and plugs do, take a look.
a7
Dout = Data out and Din = data in. Thats wat i asked for.
I'm not shure when it comes to english frases.
I'm here to learn. Or am i at the wrong place for that?
Dout = Data out and Din = data in. Thats wat i asked for.
Seemed a legitimate question to me, but you managed to find the answer yourself, so great !