Transistor with resistance controlled by the amount of input power

[Abin76]

Thanks for the diagram

 

[Abin76]

And one more thing, this may sound dumb but I need some clarification.

You connected the circuitry to the red pin of the header. If there is a 12v pin on the header, I am assuming that the red and other colors are all ground pins. How does a ground pin turn into a 12v pin? It starts out as a ground pin for red and it turns into a 12v positive after the new circuitry?

 

[dougy83]

The LEDs are normally connected between the 12V and the appropriate R/G/B pin. The R/G/B pins will be switching to 0V to let the current flow from the 12V, through the LED, and then into the 0V at the R/G/B pin.

This little circuit gets the signal from the R/G/B pin, and when it turns on and switches to 0V, the P-channel mosfet is turned on, and the mosfet effectively connects the 12V to the LED+

As an aside, You could probably not worry about the 12V PSU connection, and just use the 12V coming out of the header: it should be able to provide 3A if each of the R/G/B pins are rated for 1A

 

[dougy83]

You connected the circuitry to the red pin of the header. If there is a 12v pin on the header, I am assuming that the red and other colors are all ground pins. How does a ground pin turn into a 12v pin? It starts out as a ground pin for red and it turns into a 12v positive after the new circuitry?

The ground pin for red is used to turn on the mosfet. When the mosfet is turned on, it supplies the 12V for the LEDs

 

[Abin76]

The ground pin for red is used to turn on the mosfet. When the mosfet is turned on, it supplies the 12V for the LEDs

But how would that work. The 12v on an LED strip is supplied to all the colors. I want to be able to control each color separately after adding the circuit. If the 12v is controlled by the pwm then all colors will respond the same effects. that's why I asked why it turns into a positive charge after going through the circuit.

 

[audioguru]

Does anybody know if LED strips have common cathode or common anode?
If the LEDs are common cathode and you apply ground to the strip then a color is lighted (lit) if the pin for that color is +12V which the Mosfet shown is doing.
If the LEDs are common anode and you apply +12V to the strip then a color is lighted (lit) if you ground its pin for that color.

 

[Abin76]

Does anybody know if LED strips have common cathode or common anode?
If the LEDs are common cathode and you apply ground to the strip then a color is lighted (lit) if the pin for that color is +12V which the Mosfet shown is doing.
If the LEDs are common anode and you apply +12V to the strip then a color is lighted (lit) if you ground its pin for that color.

The LED strip is common anode

 

[EvilGenius]

Hello Good People
I read the post several times and have gathered the following.
1- Motherboard (It seems more like a controller than PC motherboard, but it does not matter), puts out common anode 1A total output.
2- LED strips are also Common Anode 12V. These strips are organized in 3 pixel per each (20ma) circuit with a series resistor. Each pixel has 3 colors RGB. Individual Vr~1.85v, Vg~3.1v, Vb~3.2v
Typical 5 meters (16.4ft), 12v common anode RGB strip burn 2A per channel for total of 6A at 12v.
3- Abin wants to be able to run more than 1A LED strips than this controller can offer.

A PMOS diagram suggested earlier will not work. You have the input correct for sinking gate, but the output also needs to be sinking (open collector). A combination of PMOS on input and NMOS on the output is needed to get the logic correct and be able to extend to 3 channel common anode RGB strip.

 

[EvilGenius]

Abin
What you are looking for is called: Data Repeater or most popularly known as RGB Amplifier.
Here is a link to a product online. Google RGB Amplifier on Ebay, or Amazon and pick one that has common anode, 12v, and at least 6A. You will also need a 12vDC 7-10A power supply for power injection to amplifier. I have seen some as cheap as $1 USD free shipping from China.
https://www.ebay.com/itm/Data-Repea...547416?hash=item3ada0f6dd8:g:orIAAOSwAuZX4uK2

If you want to build your own here is what I put together:

 

[Abin76]

The header is a motherboard header btw.
Also it runs at 2A sorry for the mistake, but i still want to run more LED strips above a total 2A anyway.
Below are the motherboard header and the manual description of the header.

 

[EvilGenius]

The header is a motherboard header btw.
Also it runs at 2A sorry for the mistake, but i still want to run more LED strips above a total 2A anyway.
Below are the motherboard header and the manual description of the header.
View attachment 104350 View attachment 104352

Abin
Look at post #29.

 

[Abin76]

Abin
What you are looking for is called: Data Repeater or most popularly known as RGB Amplifier.
Here is a link to a product online. Google RGB Amplifier on Ebay, or Amazon and pick one that has common anode, 12v, and at least 6A. You will also need a 12vDC 7-10A power supply for power injection to amplifier. I have seen some as cheap as $1 USD free shipping from China.
https://www.ebay.com/itm/Data-Repea...547416?hash=item3ada0f6dd8:g:orIAAOSwAuZX4uK2

If you want to build your own here is what I put together:

Oh thank you for this.,
So you put the signal of the LED strip header from motherboard and supply some power and it will amplify the amount of Amps to connect more LED strips correct?

 

[EvilGenius]

Oh thank you for this.,
So you put the signal of the LED strip header from motherboard and supply some power and it will amplify the amount of Amps to connect more LED strips correct?

Correct. All the functions from your motherboard will be transferred and amplified. So nothing is changed in respect to your signal and effect. You just have more power output! Happy Lighting.

 

[Abin76]

Thank you everyone for the help,
I really appreciate it,
I guess im going to buy a Data Repeater.
This problem is now solved

 

[dougy83]

I thought you only wanted to use a single Red LED strip; my bad. Glad you found a solution.

 

[Abin76]

I thought you only wanted to use a single Red LED strip; my bad. Glad you found a solution.

Oh sorry for the confusion. When I talked about the red color, I was only taking that pin as an example. I thought once I got that pin, then I can repeat that 2 more times for the other 2 colors.