OT: LED lighting configuration...

[Paul Koning]

> On Apr 29, 2016, at 3:32 PM, Bill Sudbrink <wh.sudbrink at verizon.net> wrote:
> 
> ... 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:
> 
> http://www.ebay.com/itm/Mean-Well-LPF-60D-36-AC-DC-POWER-SUPPLY-Dimmable-LED
> -DRIVER-36V-60W-CLASS2-/161857068172?hash=item25af6edc8c:g:9hQAAOSwA4dWHVn5
> 
> 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.  Constant voltage is the typical "regulated power supply".  Constant current is needed for loads whose behavior is tied to a particular current, especially if those loads have negative dynamic resistance (such as gas discharge tubes, e.g., fluorescent tubes).

If you have multiple loads that want the same constant voltage, connect them in parallel.  If you have multiple loads that need constant current, connect them in series, NOT in parallel.  The whole point of constant current applications is that the impedance of the loads is not consistent, and if you connect them in parallel, the current through each individual load will not be the correct value.

	paul