I've got a set of LED fairy lights and I'd like to be able to reduce or preferably adjust their brightness.
They're plugged into a black box power so I thought I could do something with the low voltage circuit. I'm guessing these lights are too low power to require a fancy constant current driver like bike lights do - so it's just a case of dropping the voltage somehow, yes?
Do I need a voltage regulator? I'm guessing a series resistor isn't a good idea.
Can you not just stand further away?
No.
You need to reduce the current somehow. How will depend on how they are wired. They might have a constant current driver, no reason why they wouldn't just because they aren't bike lights. More likely they are wired with a mix of series and parallel and run from a constant voltage supply. A resistor might do it in that case but you'll need one with a high enough power rating or just swap the supply for a lower voltage one. Another option is to put a FET in series and PWM them but that is getting a bit tricky unless you have the bits to hand.
Look up a PWM motor speed control/LED dimmer
Should be easy to splice into the DC side.
no. you need a current regulator.
series resistor is bad, and only really a simple hack for a single LED.
what is the voltage and current output of the power adapter?
[img] https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcT_p22y2bBHLqEgPGgxQC63b-QtJmVsNsmL43IFbmwRltlzMFDd0MVclxmN [/img]
[img] https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcTkQBXnH13m0urKZ6epy4Gfhccij6UKwPPka9NV3cLUt9JspAf7 [/img]
[url= http://www.maplin.co.uk/p/l200cv-2a-adjustable-voltage-and-current-regulator-yy74r ]Like this?[/url]
Power supply is 24V and the label says 24x0.03W which I make out to be 1.25mA for each LED hence 30mA total.
Nail polish on the LED?
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Low power ones in housings:
Something like this might do it:
[url= http://www.ebay.co.uk/itm/2Pcs-12V-40V-10A-PWM-DC-Motor-Speed-Control-Pulse-Width-Modulation-Switch-13KHz-/131175274703?pt=UK_BOI_Industrial_Automation_Control_ET&hash=item1e8aa7d8cf ]Speed controller[/url]
EDIT too slow!
ahh just saw the 24V bit, 24V ones are available. Just a case of finding UK stock if you want it quicky. For the money I don't think I would bother putting something together myself from Maplins. They may have a DC PWM motor speed control kit cheap though.
Would those PWM controllers not flicker though?
not if the frequency is high enough
Lol.. searched for LED dimmer on ebay, they are available for £1.07 from China. FFS I can't even buy the IC from Maplin for that.
Should've searched before thinking of doing it myself!
Just measure the current draw and then stick a resistor in series with it.