Forums

Rope Light Circuit

Started by Bret Cahill December 14, 2020
The sealed-up-in-plastic power supply comes with the plug, 110v U.S. or 220=
v EU.

On a 110 v AC U. S. plug the output appears to be 110 v DC and 220 AC on a =
volt meter.

The LED part of the rope light plugs into the output of the power supply.  =
It looks like two rails go the length of the LED section which can be cut e=
very meter at a marked location.  Some LEDs can burn out while the others r=
emain lit.  The LEDs are in parallel.

Do the LEDs run off the 220 AC or the 110 v DC? =20

The connector from the adapter to the rope has an orientation indicating it=
 might be DC.  If so is the 220 voltage just extraneous, part of a simple l=
ow power rectification?







In article <894d6f11-0768-4b5f-a52e-9d2343c3a72cn@googlegroups.com>, 
bretcahill@aol.com says...
> > The sealed-up-in-plastic power supply comes with the plug, 110v U.S. or 220v EU. > > On a 110 v AC U. S. plug the output appears to be 110 v DC and 220 AC on a volt meter. > > The LED part of the rope light plugs into the output of the power supply. It looks like two rails go the length of the LED section which can be cut every meter at a marked location. Some LEDs can burn out while the others remain lit. The LEDs are in parallel. > > Do the LEDs run off the 220 AC or the 110 v DC? > > The connector from the adapter to the rope has an orientation indicating it might be DC. If so is the 220 voltage just extraneous, part of a simple low power rectification? > > > > > > >
Neither. The individual LEDs are around 1 to 3 volts depending on the led type. There is a resistor to limit the current through them. So comming down the rail on each side is a low voltage DC of around 12 to 24 volts. Often a switching supply is used so the voltage is not a very good DC, but a DC with lots of ripple voltage. You can count the number of leds in a section and get an idea of the voltage. Usually each section will have a resistor and seveal leds in series. Leds are really current sensitive and not voltage . The led will take form 1 to 3 volts to start to light up. However if you do not limit the current the led burns up. So you put a few leds in series with a resistor and supply a few more volts than the leds require to light to the brightness desired. Leds operate on DC through them.
In sci.electronics.basics, Ralph Mowery  <rmowery28146@earthlink.net> wrote:
> Leds are really current sensitive and not voltage . The led will take > form 1 to 3 volts to start to light up. However if you do not limit the > current the led burns up. So you put a few leds in series with a > resistor and supply a few more volts than the leds require to light to > the brightness desired.
About ten years ago I bought an LED candelabra bulb which lasted for about five years before dying. I took it apart to see if I could figure out what's wrong (mind you, I'm not an electronics wizard). The power adapter part, which I suspected to be the problem, was turning out 150v DC. The whole thing had a circuit even I could decipher. There was a simple recifier with four diodes, two capacitors, and three resistors. Inspection of the light board showed that it had all 20 (old-school T1 3/4 size through-hole soldered) LEDs in series. I suspect that one of them failed, and that's what killed the whole. I don't think they make LED bulbs like that any more. More recent bulbs I've taken apart have been much different inside. Elijah ------ saved the LEDs but hasn't used them yet
> > The sealed-up-in-plastic power supply comes with the plug, 110v U.S. or=
220v EU.=20
> >=20 > > On a 110 v AC U. S. plug the output appears to be 110 v DC and 220 AC o=
n a volt meter.=20
> >=20 > > The LED part of the rope light plugs into the output of the power suppl=
y. It looks like two rails go the length of the LED section which can be cu= t every meter at a marked location. Some LEDs can burn out while the others= remain lit. The LEDs are in parallel.=20
> >=20 > > Do the LEDs run off the 220 AC or the 110 v DC?=20 > >=20 > > The connector from the adapter to the rope has an orientation indicatin=
g it might be DC. If so is the 220 voltage just extraneous, part of a simpl= e low power rectification?=20
> >=20 > >=20 > >=20 > >=20 > >=20 > >=20 > > > Neither. The individual LEDs are around 1 to 3 volts depending on the=20 > led type. There is a resistor to limit the current through them.=20 >=20 > So comming down the rail on each side is a low voltage DC of around 12=20 > to 24 volts. Often a switching supply is used so the voltage is not a=20 > very good DC, but a DC with lots of ripple voltage. You can count the=20 > number of leds in a section and get an idea of the voltage.=20 >=20 > Usually each section will have a resistor and seveal leds in series.=20 >=20 > Leds are really current sensitive and not voltage . The led will take=20 > form 1 to 3 volts to start to light up. However if you do not limit the=
=20
> current the led burns up. So you put a few leds in series with a=20 > resistor and supply a few more volts than the leds require to light to=20 > the brightness desired.=20 >=20 > Leds operate on DC through them.
LEDs can operate on AC, it's just not quite 50% of the time. Unless the fl= ashing is undesirable, rectification seems redundant. Also, if the goal is DC, how does the 220v AC appear as a by product? =20 A lower extraneous AC voltage might make sense but a higher voltage? That = seems intentional. Bret Cahill
The 220 v EU in-cord power supply does the same thing as the 110 v U. S.  O=
nly the plug to the wall socket is different.  If you jumper a 220 PS to a =
110 outlet you get almost the same DC and AC outputs as a 110 power supply =
plugged into 110.

The string or rope parts must be designed around the 2 different voltages. =
The 220v and 110 v rope parts look alike and have mechanically interchangea=
ble internal plugs to the power supply but they require different voltages =
to operate as intended.

If you plug a 220 rope into a 110 power supply (or 220 power supply spliced=
 onto as U.S. plug) and plug that into 110 you'll only get maybe 8% of the =
lumens as if you plugged it into 220.  This appears as about a third of the=
 brightness to the yuman eye but it may last longer.

If you plug the 110v rope and PS into 220v it'll probably be really bright =
for a few seconds before it burns out.

About 2/3 eds of the 110 rope LEDs, constantly on, burned out in 6 months o=
n 110 so for a night light it maybe better to buy the cheaper EU rope, ~ $2=
 /m w/o plug, and plug into the old 110 PS.

Rope lights flash with the AC cycle so there's been no attempt to filter sm=
ooth the DC if that is what is powering the lights.