Cut a 50 down to 20

[KarlSmith]

Hi everyone,
I need to cut down a 50 light mini set down to 20.
I need 20 to fill the last arm of a 3D star.
Any one know the way to figure out the resister I will need?

[ItsMeBobO]

You can easily make the right resister out of 30 bulbs which you stuff inside a black bag. Just hook them up in series to the shortened string of 20 and you have the right voltage.

[-klb-]

The correct resistor will be around a 20 watt unit. This is going to be annoyingly large, run very warm, and won't be cheap.

You could find some 6V, or 6.25V bulbs and re lamp the string. (6.25 gives a little room for bulbs to die, and not over voltage the rest of the string)

You could get a 48VDC power supply, and a DC controller.

[Ken Benedict]

Why not buy a string for $3.00 already made from http://www.christmaslightsetc.com/p/20-Clear-Mini-Christmas-Lights-4-inch-Spacing-Green-Wire--15179.htm ?

[George Simmons]

Ken Benedict wrote:

Why not buy a string for $3.00 already made from http://www.christmaslightsetc.com/p/20-Clear-Mini-Christmas-Lights-4-inch-Spacing-Green-Wire--15179.htm ?

+1

[Guest Don Gillespie]

Or cheaper yet get some black electrical tape and cover the bulbs your not using and tape them to the back of your star

[ErnieHorning]

You can use a single 1N4004 diode in series to give the equivalent of 54 volts of rectified AC. This should allow you to use 22 mini lights at full brightness.

If you still want only 20 bulbs:

If the original 100 bulb string was 200mA, add a 62Ω (60.4Ω) 1 watt (.4 watt).

If the original 100 bulb string was 334mA, add a 36Ω (36.2Ω) 2 watt (1.7 watt).

Edit:

The numbers in parentheses are the actual calculated values.

[KarlSmith]

I wanted a real clean installation that's why I asked about cutting down a string. The warnings about heat and expense of resistors have helped me to choose the 20 light string as suggested by Ken. That will take care of the star. I will experiment with Ernie's numbers and see what I get.

Photo to follow. When all lights are installed.

Thanks guys.

[KarlSmith]

Here is a shot of the star minus the last 20.



Attached files

[ErnieHorning]

KarlSmith wrote:

Here is a shot of the star minus the last 20.

I thought you only wanted 20 lights.

[Guest Don Gillespie]

ErnieHorning wrote:

KarlSmith wrote:

Here is a shot of the star minus the last 20.

I thought you only wanted 20 lights.

he does he needs 20 to finish his star

[jerrymac]

Wall Mart Has/Had 20 light strings (clear and blue). If so problem solved (I but a case of them or so at the end of each year for fill in strings.

Try your local Wally World also Michaels tends to have short strings.

[KarlSmith]

20 light string ordered. on UPS truck as of Fri.
The star needed 120 lights in total.
2 X 50 was the easy part and the last 20 was the problem.

[Ron Boyd]

Did you make the wire frame for the star? If so, how and what materials did you use and what was used to make the precise bends.? Thanks for any help................ 1st year using LOR

[KarlSmith]

Yes I made the star.
It is 1/8" 308 stainless steel welding rod
I first use some aluminum for test and templates.
Once I had a good pattern I switched to the SS.
I bent a large amount of the angle on a sheet metal break.
It would only go so far so I did the rest in a vise.
I made 5 "V"s and welded the tips together to form each star.
Then put one inside the other and welded them all together.
I can take and post some close ups if you need.