Driving high power LEDs

Discussion in 'General Electronics Chat' started by Lee697, Nov 19, 2014.

  1. Lee697

    Thread Starter New Member

    Aug 31, 2014
    I'm thinking of making a DIY light fitting for an aquarium, using high power LED modules. Unsure of power of each, I've seen modules up to 150W used.... I'd probably go fo multiple modules at lower power each.
    The plan is to be able to control them using a microcontroller PWM output. This is where I'm getting a bit confused.
    I understand I could drive them via a suitable FET and a resistor, but would be very wasteful of power/heat, and I should look at a constant current source to drive them.

    Can anyone give me a shove in the right direction as to what to do/search for - can I dim the LEDs with PWM from the ucontroller at the current source. Should I be looking at a commercial current source, or is this something I could build from a schematic/kit. This would run 10-12hr per day indoors, so reliability/efficiency are high priorities....

    Thanks in advance....
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
    It would not be to difficult to build one. Maybe consider three things to start:
    Do you have a power supply you would like to use?
    Do you have some LEDs you like.
    Would you rather build it or buy it?
  3. Lee697

    Thread Starter New Member

    Aug 31, 2014
    Thanks - I'd love to build one, but at this point I'm shorter on time than money! I'm planning on building my own microcontroller that I can program.
    LEDs I'm even unsure - from what I've seen on ebay, something along the lines of 10W modules, 6500K colour.
    I do have a spare 30V 15A SMPS laying around.

    ebay link
    Is this driver on ebay something like I would need? It states it can be dimmed with a 5V PWM signal, my ucontroller is 3.3V, I'm assuming I could drop a FET driver chip in between to drive the LED driver with 5V from the 3.3V signal of the ucontroller?

    Once I know what I'll need, I'll start looking at good brands - I don't trust chinese ebay stuff to run 12hr days 365d.... for long! :)
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    If you want "good brands" then hands down use meanwell LDD constant current LED drivers with suitable constant voltage power supplies. The CV power supply needs to be a few volts higher than the sum of the forward voltage rating of the series string or larger single LED module (most use a 48v supply and run as many LEDs in series as they can... usually 12 or so assuming 3W LEDs on star mounts)
    The LDD accepts a 5V PWM signal (from a microcontroller) for dimming and with the appropriate 10k pulldown resistor you can dim all the way down to "off"
    They are used all the time to build DIY LED fixtures in the aquarium world.

    Another one I would highly recommend is meanwell LPF series.. They can be plugged right into the AC outlet and do the ac/dc conversion and constant current regulation all in one package vs the LDD+regular power supply.
    The LPF can be dimmed via 10V pwm or 1-10V analog or manually via a 100k potentiometer

    Meanwell is proven as I know of hundreds of fixtures using them with very few if any problems.