| Author |
Message |
Nikki
Guest
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 Posted:
Thu Nov 17, 2005 9:35 am Post subject:
LED Christmas Lights |
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Hi Guys
I have a very limited knowledge of electronics but understand the basics
I have a question about those new LED Christmas lights. I know that an
LED does not take very much current or voltage 2-3 volts. How is it
that they can plug those things into 110v. The reason I ask is my
Daughter wants to dress up as a Christmas tree for a party. Is there
any way to rewire a string of say 25 led's and run them off a battery
pack from a drill. My husband has several of them at 9 volt or 12 volt
or a 18 volt
Thanks
Nikki
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Impmon
Guest
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| Posted:
Thu Nov 17, 2005 9:35 am Post subject:
Re: LED Christmas Lights |
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On Wed, 16 Nov 2005 23:25:45 -0500, Nikki <rickj@sympatico.ca> wrote:
| Quote: | How is it
that they can plug those things into 110v.
|
Those LEDs are in series. A string of 70 LEDs would require close to
150v. When you figure that 110v AC is merely a measurement of RMS and
not peak, adjust the value for peak volt to about 155v peak, it is
just enough to drive all the LEDs without burning them out or
requiring resistor.
Do keep in mind that all LEDS absolutely must have the same facing
polarity. All LED must connect anode to cathode of next LED, anode to
cathode of next LED, etc. If one LED is in reverse, none of them will
light up.
If you use smaller LED, it has lower voltage and you will need more to
light them. If you use big LEDs, they may have higher voltage
requirement. Check the specs before comitting to buy x LEDs.
LEDs are more than just lower electric bills, they are also safer.
Bulbs don't shatter like regular bulb so no exposed wiring or sharp
glass. Also little heat so little fire hazard as well. Finally with
proper care, those LEDs would outlast the wires they are mounted on!!!
As for the battery pack, a 9 v will probably work with 4 or 5 in
series. 12v can do 5-6, and 18 should be able to handle about 8 or 9.
--
When you hear the toilet flush, and hear the words "uh oh", it's already
too late. - by anonymous Mother in Austin, TX
Spam block in place, no emil reply is expected at all. |
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Nikki
Guest
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| Posted:
Thu Nov 17, 2005 5:35 pm Post subject:
Re: LED Christmas Lights |
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What if I rewired all the LED's on that string to parallel
Would that work
Nikki
Impmon wrote:
| Quote: | On Wed, 16 Nov 2005 23:25:45 -0500, Nikki <rickj@sympatico.ca> wrote:
How is it
that they can plug those things into 110v.
Those LEDs are in series. A string of 70 LEDs would require close to
150v. When you figure that 110v AC is merely a measurement of RMS and
not peak, adjust the value for peak volt to about 155v peak, it is
just enough to drive all the LEDs without burning them out or
requiring resistor.
Do keep in mind that all LEDS absolutely must have the same facing
polarity. All LED must connect anode to cathode of next LED, anode to
cathode of next LED, etc. If one LED is in reverse, none of them will
light up.
If you use smaller LED, it has lower voltage and you will need more to
light them. If you use big LEDs, they may have higher voltage
requirement. Check the specs before comitting to buy x LEDs.
LEDs are more than just lower electric bills, they are also safer.
Bulbs don't shatter like regular bulb so no exposed wiring or sharp
glass. Also little heat so little fire hazard as well. Finally with
proper care, those LEDs would outlast the wires they are mounted on!!!
As for the battery pack, a 9 v will probably work with 4 or 5 in
series. 12v can do 5-6, and 18 should be able to handle about 8 or 9. |
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Impmon
Guest
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| Posted:
Fri Nov 18, 2005 12:28 am Post subject:
Re: LED Christmas Lights |
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On Thu, 17 Nov 2005 06:38:01 -0500, Nikki <rickj@sympatico.ca> wrote:
| Quote: | What if I rewired all the LED's on that string to parallel
Would that work
|
Well, yeah but only if you have a 2v source.
--
When you hear the toilet flush, and hear the words "uh oh", it's already
too late. - by anonymous Mother in Austin, TX
Spam block in place, no emil reply is expected at all. |
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Dave
Guest
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| Posted:
Fri Nov 18, 2005 1:35 am Post subject:
Re: LED Christmas Lights |
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I think she meant wire groups of 8 or 9 LEDs in parallel.
"Impmon" <impmon@digi.mon> wrote in message
news:ssipn1hv806k6a19l4fr0u6dq5m3eg3i1m@4ax.com...
| Quote: | On Thu, 17 Nov 2005 06:38:01 -0500, Nikki <rickj@sympatico.ca> wrote:
What if I rewired all the LED's on that string to parallel
Would that work
Well, yeah but only if you have a 2v source.
--
When you hear the toilet flush, and hear the words "uh oh", it's already
too late. - by anonymous Mother in Austin, TX
Spam block in place, no emil reply is expected at all. |
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Bill Bowden
Guest
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| Posted:
Fri Nov 18, 2005 1:35 am Post subject:
Re: LED Christmas Lights |
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There is an LED resistor calculator at
http://ourworld.compuserve.com/homepages/Bill_Bowden/led.htm
There are several examples of connecting a few LEDs to various
batteries. For example, you can hook 4 red LEDs in series and add a 270
ohm resistor to connect to a 12 volt battery. Connect another 4 leds
plus resistor for a total of 8, etc.
-Bill |
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Rich Grise
Guest
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| Posted:
Fri Nov 18, 2005 1:35 am Post subject:
Re: LED Christmas Lights |
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On Thu, 17 Nov 2005 06:38:01 -0500, Nikki wrote:
| Quote: | What if I rewired all the LED's on that string to parallel
Would that work
|
Only if each has its own series dropping resistor, which shouldn't
be too hard. But, as has been mentioned, you can put strings of 2
or 3 or 4 (or whatever, depending on the voltage) LEDs in series
with one dropping resistor for the set.
LEDs don't cooperate well in parallel - one will hog the current,
and you'll get a cascade failure.
Good Luck!
Rich |
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Nikki
Guest
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| Posted:
Fri Nov 18, 2005 5:35 pm Post subject:
Re: LED Christmas Lights |
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Rich Grise wrote:
| Quote: | On Thu, 17 Nov 2005 06:38:01 -0500, Nikki wrote:
What if I rewired all the LED's on that string to parallel
Would that work
Only if each has its own series dropping resistor, which shouldn't
be too hard. But, as has been mentioned, you can put strings of 2
or 3 or 4 (or whatever, depending on the voltage) LEDs in series
with one dropping resistor for the set.
LEDs don't cooperate well in parallel - one will hog the current,
and you'll get a cascade failure.
Good Luck!
Rich
Thanks guys |
I tried the leds in parallel about 25 of them and only a couple of them
came on. I ended up using the mini lights with a 4 volt 6.5 a/h that
should last a little while but not as long if it were the led's
Thanks for your help
Nikki |
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