RGB LED project

How can Rpi Python PWM GPIO pins control brightness of white LED strips of 3 to 4 1W 350mA power LEDs?

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I’m trying to figure out my first RaspberryPi (3B+) project, where I’m going to manage 3-4 White LED Strips with following specifics for a single one:

  • 350mA Constant Current (max 400mA)
  • 39,6V Voltage
  • 13,86W for each LED module
  • Dimmerable LEDs

I’m trying to avoid the “hard way” for the moment (not for lazyness; I want to start gradually), so I would like to avoid any DIY electrical circuitry (if not absolutely mandatory), but I’m trying to find a specific dimmer/multi-dimmer module to manage the LEDs:

  • attachable to RPi GPIO
  • able to provide the right amount of power to the LED(s)

Can you help me to find such a module or is it just “a dream” and I need to dirty my hands 🙂 ? In this case … could you suggest to me a feasible solution or explanation?

Thanks a lot for your help and sorry if I have not provided all requested info.ledShareEditFollowClose 2Flagedited 8 hours agotlfong013,51633 gold badges77 silver badges2222 bronze badgesasked yesterdayEchoes_8610722 bronze badges New contributor

  • RGB or white? single led or stripe? (1) aliexpress.com/popular/led-rgb-dimmer.html, (2) electronics.stackexchange.com/questions/552849/… – tlfong01 yesterday    
  • 1Sorry … Stripes and White – Echoes_86 23 hours ago
  • 1Ah, for dimming white LED stripes, Alibaba has cheap solutions for you. DIY, on the other hand, is very hard. See my comments in the following question: LED Driver for street light 50W: electronics.stackexchange.com/questions/552849/…. Cheers. – tlfong01 23 hours ago    
  • 1@tlfong01 could you please explain or link some material where I can understand how I can get the connections? I mean “where” I need to plug the strips, the power supplies, etc. I’m missing the part: out of GPIO I have 3mA per Pin. I need 350mA. Where I can get it from? Do I need an auxiliary power supply? How can I link it ? Thanks a lot! – Echoes_86 23 hours ago
  • 1Just a quick reply. (1) You need a transistor to amplifier the GPIO pin’s small, less than 5mA current to bigger than 300mA current. For example, you can use a 2N2222 transistor to control a 20mA status/indicator LED, or 100mA for a power RGBYW LED. (2) You can then use a GPIO output pin in PWM mode connected to the Base of the 2N2222 to control the Collector current and thus the brightness of the power LED. – tlfong01 19 hours ago   
  • 1You might find useful references in this chat: chat.stackexchange.com/transcript/119380/2021/2/5 – tlfong01 19 hours ago   
  • 1You might be interested of the following: AliExpress Diymore LED Lamp Driver PWM Dimmer DC7-30V to DC1.2-28V 350mA 1W – US$1 es.aliexpress.com/item/…. Cheers – tlfong01 18 hours ago    
  • (1) Your question mentioning “39,6V” seems confusing, please clarify. (2) You spec of “13.86W” seems too strict. Perhaps you can give us a link to your stripe” Cheers. – tlfong01 8 hours ago   
  • PT4115 seems to fit your spec well. (1) PT4115E 30V, 1.2A Step-down High Brightness LED Driver with 5000:1 Dimming Datasheet – PowTech electroschematics.com/wp-content/uploads/2014/07/… – tlfong01 8 hours ago   
  • I must confess that I have not yet tried this PT4115E LED driver, so I am just suggesting, withou any guarantee it works OK. Anyway, I got nothing to do this gloomy Covid-19 locking down Sunday afternoon, so perhaps I should investigate further and try to give a little bit more advice for newbies how to start. Please stay tuned to the coming answer. I am giving a “live” step by step answer. You are welcome to make comments and counter suggestions on how my live answer should go. Cheers. – tlfong01 30 mins ago   

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1 Answer



How can Rpi Thonny Python PWM GPIO pins control brightness of white LED strips of 3 to 4 1W 350mA power LEDs?

It would be nice to start easy with a cheap module, and later do a DIY project using ICs to assemble one’s own module which would hopefully be more flexible for newbies’ general understanding and applications.


Part A – Project Plan

User requirements

The OP seems to have already done a lot of research, and come up with a very detailed specification. I found his requirements a bit too tight or specific, so I have taken liberty to modify it to become more flexible and newbie friendly. The modified requirements are summarized below.

  1. The OP specified white LED stripes of a number of 1W, 350mA, white power LEDs. I would change it to 1~3W, 350mA~1,000mA RGBYW power LEDs.
  2. The OP specifies, for each module, 39,6V (= 39.6V?, ~= 40V) Power supply voltage, and 13,86W (= 14V, ~= 15W). I would change it to start with (a) 12VDC to 24VDC, (b) 12W to 40W maximum.
  3. The OP specifies Rpi GPIO controlled dimming modules. I would modified it to Rpi Thonny python with GPIO output pin in PWM mode. I always think thonny python is most newbie friendly than C++.

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