can relays help wattage?

Discussion in 'The Projects Forum' started by solderedmyfinger, Mar 8, 2012.

  1. solderedmyfinger

    Thread Starter New Member

    Feb 11, 2012
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    Patience requested as I am not yet as evolved as the rest of you bloggers.

    I've successfully built a solar charging 6v DC battery powered led system (steroided garden light). Success! even with switching! With my bloated confidence, I upped the load to two 2.5W led bulbs and encountered a loss in their luminosity (compared to direct [parallel] connect to batt.).
    'Expert man' says I should install a relay between the output (-) side of the leds and the NPN/neg. battery lead.
    I don't see how this would help. I'm reluctant to keep adding crap when I'm uncertain of my own crap. Does anyone think that this relay would solve my problem?
    ...Is anyone suspicious that 'expert man' is hiding nearby; pointing and choking back laughter?
    Please help the lower primate understand.
     
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
    2,936
    488
    Please post a simple diagram. What was the load before?

    You connected LEDs directly to a battery? No current limiting resistors?

    A relay will not help to change luminosity of a LED, at least I can't see how.
     
  3. BillB3857

    Senior Member

    Feb 28, 2009
    2,400
    348
    Use the transistor to control the relay and the relay to control the LEDs
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,107
    3,038
    For such a small system, you don't need any relays. Relays are great for isolating one power supply from another (DC can be used to switch AC, for instance) or for switching "large" currents. You have neither of these situations. Transistors, particularly MOSFETs are more useful in this kind of application.

    Relays and transistors are little more than switches. Without a schematic, we can't guess what you want to "switch". Adding a switch won't give you more power, although it might be used to prevent battery power being wasted thru the panels when it's dark out. A blocking diode is usually used for this reason.

    Perhaps you want to switch the LEDs on and off based on ambient lighting? That's how many garden lights work - they use a separate light detection circuit and a CdS cell to work a switch. Definitely a transistor application.
     
  5. solderedmyfinger

    Thread Starter New Member

    Feb 11, 2012
    2
    0
    Outstanding, Wayneh et al! Since my direct-to-battery testing concluded that power supply/power needed are so similar, I'm scaling down the circuitry to see what happens (switching diode, resistors only--no transistors). I'm mad I tell you...Mad! (lol). Moronic? Thank goodness this stuff is inexpensive.

    sorry for the late response, fergot which forum I was in.
     
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