Hi, I purchased a set of Xmas lights with a built in flasher control plug/ transformer ( control is on the transformer) I don't want my lights to flash so I purchased another transformer with out the flash control but when I turn on the lights now there are only 2/3 of the lights lit, can anyone help?
Xmas lights indoor transformer question **help**
- Thread starter Rich1819
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The style of LED lights available has recently changed in the last two years. These days you seem to get as you describe a switch mode PSU on a plugtop with integrated control unit and a two pin connector out to the lights and running around 32-34v
Before that, you used to get a control unit separate from the power supply (which used to be 24v in most cases). This seemed to be a thing which has carried on from SELV filament sets... which are in 95% of cases 24v.
I expect the change is down to a redesign to allow them to be made cheaper... initially it was cheaper to just re-use a design for which production was already set up for.
Now I need to investigate the set I have on my tree, but I expect the setup will be something like a DC supply which the controller flips the polarity of many times a second (far too fast to see) in order to effectivly get two channels down a two core cable. The two channels of LEDs will be connected in series with a diode to protect them from reverse currents, and be over driven to make up for the fact that they will see at max a 50% duty cycle.
If that is indeed the case (and I am guessing until I have investigated) then I would have thought a suitable AC supply would keep allow them to all be on. But I am taking a stab in the dark here!
Before that, you used to get a control unit separate from the power supply (which used to be 24v in most cases). This seemed to be a thing which has carried on from SELV filament sets... which are in 95% of cases 24v.
I expect the change is down to a redesign to allow them to be made cheaper... initially it was cheaper to just re-use a design for which production was already set up for.
Now I need to investigate the set I have on my tree, but I expect the setup will be something like a DC supply which the controller flips the polarity of many times a second (far too fast to see) in order to effectivly get two channels down a two core cable. The two channels of LEDs will be connected in series with a diode to protect them from reverse currents, and be over driven to make up for the fact that they will see at max a 50% duty cycle.
If that is indeed the case (and I am guessing until I have investigated) then I would have thought a suitable AC supply would keep allow them to all be on. But I am taking a stab in the dark here!
For the love of God, would it not have been a much sensible idea to just purchase a lighting system that did not flash, right from the get go?
Can you get them? I'm increasingly frustrated by xmas lights. They come with 4 channel controllers but usually only have 2 connected. And they all have that epeleptic mode where they Flash stupidly fast. Perhaps to make up for only having 2 channels. And whatever mode you select it has 3 speeds of that mode! No! Stop it! I selected the perfect speed! Ffs!
A more recent thing is those "icicle" light chains wired wrongly. Rather than flashing up to down they Flash side to side. They are meant to resemble snow fall but since when did it snow sideways?!
And don't get me started on these polarity driven sets. Clever but the ultimate in producing to a price.
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Yes they called "static Christmas lights"
I recently opened up a controller from a cheap solar powered LED string. It bucked up the 1.5 volt supply from an AA cell to 3 volts which was supplied to the string. All LEDs connnected in parallel so each LED element got the 3 volts. No resistors. I then tested one LED to destruction by increasing the voltage and measuring the current it took...
Increasing voltage slowly from 3 to 6 volts was OK with the LED geting very bright. Above 6 volts the brightness started to reduce and the device went out at 9 volts but was still drawing current.
Repeated the test on another LED but stopped at 6 volts. When the voltage was taken down to 3 volts the LED was much dimmer than it was before at 3 volts so at 6 volts the LED element had been damaged.
The results of tests on four other LEDS suggested there was a "resistance" in series with an LED junction inside the LED element and that this resistance was the same (+/- 10 % ) for all the LEDs. This resistance has to have been designed into the construction of the LED and has to be a resistively doped layer in the LED element. Very low cost implication to add one more silicon layer in the mass - production of billions of LEDs and a massive saving in not having to solder in a resistor to each LED lamp.
But there is still a small puzzle as to how the strings are assembled. The quality of the soldering suggests hand soldered. The twisted pair cable has no obvious polarity marking so how does the assembly worker know which way to connect the LED. ( if the 3 volt supplied to the string was AC then the LEDs could be either way round but it is DC )
Increasing voltage slowly from 3 to 6 volts was OK with the LED geting very bright. Above 6 volts the brightness started to reduce and the device went out at 9 volts but was still drawing current.
Repeated the test on another LED but stopped at 6 volts. When the voltage was taken down to 3 volts the LED was much dimmer than it was before at 3 volts so at 6 volts the LED element had been damaged.
The results of tests on four other LEDS suggested there was a "resistance" in series with an LED junction inside the LED element and that this resistance was the same (+/- 10 % ) for all the LEDs. This resistance has to have been designed into the construction of the LED and has to be a resistively doped layer in the LED element. Very low cost implication to add one more silicon layer in the mass - production of billions of LEDs and a massive saving in not having to solder in a resistor to each LED lamp.
But there is still a small puzzle as to how the strings are assembled. The quality of the soldering suggests hand soldered. The twisted pair cable has no obvious polarity marking so how does the assembly worker know which way to connect the LED. ( if the 3 volt supplied to the string was AC then the LEDs could be either way round but it is DC )
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Although tricolour LED's often have a common cathode or anode, there are other ways to select colour including polarity. As already said if you don't want them to flash buy some not designed to flash.
The LED is a current dependent device to make it into a voltage dependent device some form of driver is required. It could be a simple resistor or a complex chip it can be built into the LED or a separate device it can even be designed to read wave form clipping as a command to reduce current. Looking at the device we really have no idea what is inside so modifying is always hit and miss.
bernardgreen's experiment was similar to mine. We had heard by flashing the LED you could increase the output without burning it out. So using a 555 timer and a relay chip we set the mark/space ratio and flashed the LED at around 1kH and slowly increased the current. We also did the same without flashing it. As with Bernard we found once damaged by over voltage they did not recover. The lux meter showed no gain by flashing but to our eye they did seem to get brighter. At an even mark/space ratio pulsed 30 mA gave same output as steady 15 mA clearly it was the total heat dissipation which caused them to survive or fail. Although flashing Christmas lights are a lot slower I would still think using them without flashing could over drive the LED's and cause them to fail. Also the different colours work with different voltages.
The LED is a current dependent device to make it into a voltage dependent device some form of driver is required. It could be a simple resistor or a complex chip it can be built into the LED or a separate device it can even be designed to read wave form clipping as a command to reduce current. Looking at the device we really have no idea what is inside so modifying is always hit and miss.
bernardgreen's experiment was similar to mine. We had heard by flashing the LED you could increase the output without burning it out. So using a 555 timer and a relay chip we set the mark/space ratio and flashed the LED at around 1kH and slowly increased the current. We also did the same without flashing it. As with Bernard we found once damaged by over voltage they did not recover. The lux meter showed no gain by flashing but to our eye they did seem to get brighter. At an even mark/space ratio pulsed 30 mA gave same output as steady 15 mA clearly it was the total heat dissipation which caused them to survive or fail. Although flashing Christmas lights are a lot slower I would still think using them without flashing could over drive the LED's and cause them to fail. Also the different colours work with different voltages.
LEDs that flash at say one cycle per second are often being switched at 50 or 100 Hz when driven from a mains powered PSU and they may be also modulated at higher frequency pulse width modulation when they can be faded
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