OT: LED lighting configuration...
paulkoning at comcast.net
Fri Apr 29 15:16:14 CDT 2016
> On Apr 29, 2016, at 4:10 PM, Bill Sudbrink <wh.sudbrink at verizon.net> wrote:
> Paul Koning wrote:
>>> On Apr 29, 2016, at 3:32 PM, Bill Sudbrink <wh.sudbrink at verizon.net>
>>> ... The "bulbs" are labeled:
>>> 15F18120-45 15 watt 36vdc constant current
>>> I'd like to put four in a fixture and I'm trying to
>>> understand what kind of driver I need and how to wire
>>> it. I was thinking of using a Mean Well LPF-60D-36
>>> like this:
>>> and wiring the "bulbs" in parallel to it. But after
>>> realizing that I'm not completely sure what a "constant
>>> current" power supply does and doing a little "googling"
>>> I don't know if that's the right approach.
>> A constant current supply is one that delivers a constant
>> current to a varying load (within limits) just as a constant
>> voltage supply delivers a constant voltage to a varying load.
> Ok, I figured that much. The problem/question is why there
> are no Amp ratings on anything? Assuming the DC equation:
> Watts = Amps X Volts
> I want a constant current supply that "pushes" 0.41 Amps.
> A little more googling reveals that the above supply is
> rated "1.67A output". This seems to support the W=AV
> theory. So, do I want a PS labeled "15 watt 36vdc",
> regardless of how many bulbs I want to drive? You say
> "within limits". What specification do I look for to
> understand the limits?
15 watt 36 V is an odd spec for a device that needs constant current. What it seems to translate to is 400 mA device current, 36 volt nominal operating voltage. That's perhaps 10-12 LEDs in series, since each has a forward voltage around 3 volts, perhaps a bit more.
If you have a supply rated for constant current operation, 36 volt or so, settable current, you could use that, crank the current setting down to 400 mA. If it's a fixed supply (36 volts 60 watts, i.e., 1.66 A) then that would not work.
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