Cutting lights

[drawding]

I could not find an answer via a search of the forum so I figured I'd ask it here.

 

I have 6 mini trees on one string.  I'd like to cut the trees so I can control them each on their own channel.  I actually have two strings so I could have 12 matching trees.  

 

I know from reading that normally you can't just cut stings of lights as it would increase the voltage to the remaining bulbs.  But hooked to a LOR controller can't you just run the strings at a lower intensity?  Wouldn't this drop the voltage and prevent the bulbs from prematurely burning out?

 

Thanks for and advice.

[robongar]

If the lights are LED's, there are probably rectifiers each end and probably some between, from the start on tree 1 to the end of probably tree 3 plus From tree 4 to tree 6. The rectifiers convert your 110 AC voltage to 120/130 volts DC. ( on the lights I measured last week)

Your LOR controller out put is the same voltage as you put in. 110 volts AC

I'm sure you can probably work the rest out yourself.

[drawding]

No they are not led.  They are regular bulbs.  I bought them to line a sidewalk but I figured if I could separate them and have 12 trees to control it would be a fun/cheap project.

[Orville]

It depends on how the strand is wired and number of bulbs, most 50 count L.E.D. strands can be cut in half to make two 25 count L.E.D bulb strands.   100 count can be count in half to make two 50 count strands.    But again it depends on the strand is wired if this can be done.   To locate where to cut a strand in half, say a 50 count, count to the 25th L.E.D. in the strand, if there are only TWO wires {not 3}, the strand can be cut in half between the 25th and 26th L.E.D. bulb, then just add a new male plug to the strand that has the female end on it, you can also add a female end after the 25th bulb, just in case you ever need or want to extend the strand again.    Each half of these type strands get the same voltage, 110-120VDC on each half, and is why they can be cut like this.   If they have a 3rd wire all the way through, then they can't be cut.  On a 100 count strand, the cut would be on the two wires between L.E.D. bulb #50 and #51.

 

Hope this answers your question.

 

BTW: 70 count L.E.D. strands can sometimes be cut to make two 35 count strands, cut at the 2 wires between L.E.D. bulb #35 and #36, again if a 3rd wire is present all the way down the strand, they can't be cut..   And most often other L.E.D. strands can't be cut down if less than 50 count on a strand.  Larger strands over 100 may or may not be cut at their halfway point.   Don't know about sealed strands, but I've cut many a big box store brand of L.E.D.'s in half like this and still using them going on 10+ years now!

Edited December 14, 2015 by Orville

[drawding]

Thanks for the response.  That is what I've read in other places.  I've also read that if you reduce the number of lights on the string more than 1/2 you need to add a resistor to lower the voltage and not fry the bulbs.  

 

My question is if you take the number of bulbs you have after cutting and multiply by the voltage of the bulbs you can determine how much excess voltage there will be in the string.  If you lower the intensity on a channel in LOR then you are effectively lowering the voltage to the string.  So my theory is that if I put a meter on the channel output and lower the intensity it to match the reduction in voltage calculated earlier you should be able to run this shortened string at full bulb output without fear of damage.  As long as you don't exceed that new max voltage everything should work like normal.

 

I have to believe that after all the years of people using LOR products that no one has tried this?  

Edited December 14, 2015 by drawding

[Orville]

The cut strands are the same voltage as if they were together, no difference.   Some have rectifiers on each end, some have resistors or capacitors inside the socket with the L.E.D. bulb that compensates for not having a rectifier circuit on the strand.

 

So even if you cut a cuttable strand, the voltage is still the same across that new, smaller strand, if 110-120VAC, it will still be 110-120VAC.

 

The only difference that would change the voltage requirements are if you take a multi-color strand and make it all a single color, depending on the color of the L.E.D. bulb is what determines how much voltage, capacitance or resistance is required to maintain the proper voltages to prevent damage in a strand thusly converted from multicolored to solid, then yes, you'd have to figure out the voltage, resistance and/or capacitance you'd need to use them, even at lower intensity, it would still be smarter to know these differences and compensate for them correctly.

 

Because if you forget or someone decides to mess with your controllers by moving your cords around, that strand that you think is on a low power channel, may now be on a full power channel, so it's not really a smart move just to think lowering the voltage on that channel in a sequence would keep you protected.  

 

And if the strand got the wrong voltage{higher} that it couldn't handle, chances are it's going to get extremely hot, and I mean hot enough it could melt the wires and combust, starting a fire, which could burn down your home or a neighbors home down.   Not something you really want to do.  

 

Have to toss the warnings out there, folks need to know that just lowering the voltage on the controller via the sequence is not really a very good idea or a way that this should be done without some form of possible, and very damaging consequences that could occur!

Edited December 14, 2015 by Orville

[Steven]

Like Orville said, running reduced voltage strings at a dimmed level will work, but is not safe in practice. (Perhaps someone in a 240v mains country has used North American lights this way and could comment?)

 

Since you're dealing with cheap incandescent mini lights, a better way is to buy some cheap strings of lower voltage bulbs and replace the bulbs. Common strings are 12v (10-15 bulbs), 6v (20-25 bulbs), 3.5v (35 bulbs), 2.5v (50-bulbs). 100-bulb strings are almost always 2 strings of 50. Sometimes 50-bulb strings are really 2 strings of 25.

 

Note that 2.5v * 50 is 125v, which is actually more than the actual voltage. This lets these strings run a little cooler, and allows for some to burn out (they have bypass shunts), while still having no more than the rated voltage on each bulb. 3.5v bulbs also have bypass shunts. 12v bulbs do not have shunts, so when one burns out, they all go out, and you have to hunt for the bad bulb.

[Orville]

I've bought really small strands of incandescent bulbs at most Dollar stores for $1!  Usually these are 10 count and 20 count strands, 10 count use 12V bulbs, the 20 count use 6V bulbs.  

 

Only draw back is if you need to connect them end to end, most of these smaller $1 store variety short strands do not have the female end on the end to allow for strand to strand connections, but one could be spliced in behind the last bulb to supply power to the next strand if needed.   But you'd have to splice in one for each strand you need to connect to each other, if needed.   But that's the only real drawback to the 10ct/20ct strands I've picked up for a $1 at the Dollar stores.   Occasionally you might get lucky and they'll have the female end, but it's not that common with these smaller strands.

[drawding]

Since I'm a 1 man show and these trees would have their own dedicated controller the chance of a mishap would be very low but accidents do happen.

 

Replacing the bulbs does seem like the safest option but I'm not even sure if it would be worth the time/expense.  I just happened to have these and though that maybe I could repurpose them. It may just be easier to restring the trees rather than mess with switching the bulbs out. I'll have to check the dollar stores around here and see if they have these short strings.  I don't need to connect them end to end, each tree needs to go to a channel on the controller.  That was the reason for cutting them in the first place.

 

Thanks for all the info!

Edited December 15, 2015 by drawding