What’s the plus side of LED drivers?

Discussion in 'General Electronics Chat' started by paulled, Aug 12, 2016.

  1. paulled

    Thread Starter New Member

    Aug 5, 2016
    2
    0
    Hey all, I’m looking for a simple answer here, and I’ve got a few questions about LED lighting and resistors. Take a look:

    1) Can a simple resistor power LED?
    2) Will a variable resistor allow me to dim LED?
    3) What is the difference between using a variable resistor and an LED dimmer?
    4) What is the difference between using an LED driver and a fixed resistor?
    5) What does it take to upgrade to an LED driver from a system of incandescent lighting using a 24v system?

    Thank you for any help
     
  2. Morvan

    New Member

    Jun 24, 2014
    11
    2
    Hi. A simple resistor can do it, if you mean limit the current to drive the led. To power up, literaly, nop;
    2) a variable resistor can dim led. In fact, current will be slightly controlled by resistor value;
    3) a led dimmer will provide thinnest control over current;
    4) answer four is responded by this and vice-versa; and
    5) you will need a driver to operate at 24v and deliver amount required by led matrix.
     
  3. dl324

    Distinguished Member

    Mar 30, 2015
    3,242
    619
    Welcome to AAC!
    No. A resistor isn't a power source.
    Yes.
    Some dimmers will use PWM to control brightness.
    A driver will most likely be a current source/sink and will maintain a more constant current with supply voltage variations. Current limited by a resistor will vary with supply voltage.
    Need more information. Most incandescent lights in my locale are operated from 120VAC.
     
    GopherT likes this.
  4. paulled

    Thread Starter New Member

    Aug 5, 2016
    2
    0
    Thank you for your inputs!

    So here is how I understand this atm. Microcontrollers aren’t necessary – in fact, they are pretty useless. People use drivers because they’re designed for LED. Resistors can work, but they have to be specifically designed, and most people don’t take the time to do it right. Is something like this OK?
    http://grealpha.com/news/a-paradigm-shift-in-lighting-management-systems-1/
     
  5. dl324

    Distinguished Member

    Mar 30, 2015
    3,242
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    What is your application? Do you have a schematic?
     
  6. #12

    Expert

    Nov 30, 2010
    16,284
    6,797
    This really isn't a, "Consumer Reports" website. Sometimes we can spot a fake, but not having one of these products available for testing means anybody here would just be guessing. And, what dl324 said, "OK for what?" Do you want to go to the highest possible level of complicated, internet connected circuitry for an LED light?

    Personally, I prefer the "switch on the wall" method. I arrive, flip the switch, and the light comes on.
    If I wasn't there, I wouldn't need the light on.
    Why I would want to go through the internet to turn the light on escapes me.
     
  7. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    To make burglars think someone is in.

    Byte magazine did a long series of articles based on the X10 system - primarily about home automation, but some of it was about home security, and AFAICR: there was some delving into the then fledgling internet.

    The radio station I listen to has been running adverts for a door intercom that calls your mobile - answer the call and talk to whoever rang your doorbell and pretend you're in.
     
  8. Tonyr1084

    Active Member

    Sep 24, 2015
    535
    86
    I can turn on ANY light in ANY room of MY house from ANYWHERE in the world. Why would I want to turn a light on in a room in which I am not? Also, I can turn on any light in any room of my house from anywhere in the world - SO CAN HACKERS!

    I wouldn't want to be fast asleep in my bed and have some hacker switching my light on and off repeatedly until I get up out of bed and remove the light bulb from the socket.

    I DO have some lights on timers. Some lights are connected to motion detectors.
     
    #12 likes this.
  9. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    1,438
    368
    There isn't much truth in any of those statements.
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    An LED driver module might be SMPSU and will probably keep the brightness constant over a range of supply voltages - if it has buck/boost topology, the supply voltage can be either above or below the combined Vf of an LED chain.

    A basic current limiting resistors converts some of the power to heat. If you have a PSU with very stable output voltage, your resistor doesn't have to absorb much variation and you can maybe have an extra LED in the chain and less volt drop across the resistor (less wasted power). With a battery - the resistor has to absorb a lot of variation, It has to limit the current to a safe value when the battery is fresh, the lees proportion of the total voltage dropped by the resistor; the more noticeable dimming as the battery runs down. You can use less series LEDs and a bigger resistor to reduce the dimming effect - but it wastes more power and you get less LEDs.

    A simple 1 or 2 transistor current limit circuit will maintain constant brightness, but I2R losses in the transistor are no better than I2R losses in a resistor, and the current limit circuit takes a chunk out of your voltage overhead.
     
  11. #12

    Expert

    Nov 30, 2010
    16,284
    6,797
    I have other methods.
    Mine is the only house on the block with outdoor lighting. I put up (2) 20 ft poles with HPS lights. Walking into my yard is like walking on to a used car lot at night compared to every other house on the block. All my windows are mirrored. There is always an extra car at my house. My neighbors have known me for 38 years and have seen me working or walking (for exercise) at all hours of the day and night. My activities, like lawn mowing, picking up the newspaper, loading the truck, going to work, and how long I'll be gone are completely unpredictable.

    Other people organize their security in other ways.
     
    shortbus likes this.
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