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jacques1mouton1

DIY LED control question

4 minutes ago, jacques1mouton1 said:

Thanks for the advice, do you mean like this? (I will only be using 3 LED modules)

Capture.PNG

The load goes in series between the molex and the transistor, like this:

Npn_switch.png

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Posted · Original PosterOP

I picked up a 12V 60mA 3xLED module (picture included). I want to use this with an Arduino nano that will generate a PWM signal with a duty cycle determined by the value of a potentiometer. I simulated the circuit that I plan on using with the results close enough to the required specifications (Tested with a signal generator and a lab power supply set to 12V and the LED module works as expected). What I would like to know, before I blow up my power supply, is if it would be safe to power this circuit from a Molex connector with the 12V going to the circuit and 5V to the Arduino for power. Are there any other precautions that I should take?

 

This is to illuminate my rear IO panel in the dark but I also want to be able to adjust the brightness. Linus posted a video quite a while back, but there is no way using his configuration to dim the LEDs.

 

Capture.PNG

led_module_3_smd_5050-12v.jpg

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@jacques1mouton1

The base-emitter junction of a NPN acts like a diode, so you will need a resistor in series with the base to limit base current. For the given load 1K will be fine. Then you can simply connect the led strip between the 12V molex(led strip +) and the collector of the transistor (led strip -), no additional resistors needed as the led strip includes them.

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It is suggested they will draw approximately 1.2 amps per meter at full load at 12 volts you should be fine as long as you provide 12 volts 9 volts can do it but at a cost of brightness


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Posted · Original PosterOP
6 minutes ago, Unimportant said:

@jacques1mouton1

The base-emitter junction of a NPN acts like a diode, so you will need a resistor in series with the base to limit base current. For the given load 1K will be fine. Then you can simply connect the led strip between the 12V molex(led strip +) and the collector of the transistor (led strip -), no additional resistors needed as the led strip includes them.

Thanks for the advice, do you mean like this? (I will only be using 3 LED modules)

Capture.PNG

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Posted · Best Answer
4 minutes ago, jacques1mouton1 said:

Thanks for the advice, do you mean like this? (I will only be using 3 LED modules)

Capture.PNG

The load goes in series between the molex and the transistor, like this:

Npn_switch.png

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Not like this ^^ whenever the gate opens it will short the 12 v to the - and killing your supply :S

From the V1 + insert the 12 V led in the line so it sits between the +12v and the gate

 

Edit: typed my reply when yours popped up @Unimportant ;) 

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Posted · Original PosterOP
Just now, Unimportant said:

The load goes in series between the molex and the transistor, like this:

Npn_switch.png

Thanks for the help, will make it like this. (It has been a long while since I worked with transistors and remember very little)

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Just curious do you have an rgb header on your mobo? I have 2 meters powered by my board wrapped my desk with rgb works fine my boards headers are both good for 2 meters that way my desk is synced with the rest of my hardware you can use a splitter to achieve this


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20 hours ago, jacques1mouton1 said:

Thanks for the help, will make it like this. (It has been a long while since I worked with transistors and remember very little)

For higher loads you might want to consider using a logic level mosfet like the IRL540. I'm building a 5 channel LED controller for my fishtank. Prototype is done.

mosfet's though require voltage on it's gate instead of a current to open and let current flow.

 

Here is a schematic that could work for you using a mosfet.

599567ee3c9c2_circuit(1).png.74c8a1a7938dca5f05ee1dfd14bede3f.png

Live example: http://everycircuit.com/circuit/5998474636296192


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