bulb question - 12v/20W vs. 6v/5w

M

Mike

Guest
Hi folks,

Just a couple of days before halloween, it's important for your light-up
pumpkins and displays to work properly. Unfortunately, one of our displays
blew a bulb the other night and my wife is somewhat upset about it.

So, after going to four stores (two home depots, one lowes, one wal-mart),
nobody had the replacement build. Home depot had a spot for the original
(6v/5w), but both stores were out! So, I picked up at lowes today the
closest match I could find: 12v/20w. Thinking I can just apply some
resistors in-line with the bulb, I figured I could have this working again.

Here's my assertion:

The original bulb is a MR11 type, 6v, 5W. The power supply output is 6VAC,
1000ma. How can I make this bulb work? Sorry if this is a naive question.

Thanks.
 
you don't.....
the 12V bulb would only glow a bit, and overload the transformer since it's
resistance is too low

only "fast" solution would be to use a bicycle bulb, usually they are about
6V


"Mike" <no_spam@comcast.net> wrote in message
news:X8idnZMeg_yVER_cRVn-ig@comcast.com...
Hi folks,

Just a couple of days before halloween, it's important for your light-up
pumpkins and displays to work properly. Unfortunately, one of our displays
blew a bulb the other night and my wife is somewhat upset about it.

So, after going to four stores (two home depots, one lowes, one wal-mart),
nobody had the replacement build. Home depot had a spot for the original
(6v/5w), but both stores were out! So, I picked up at lowes today the
closest match I could find: 12v/20w. Thinking I can just apply some
resistors in-line with the bulb, I figured I could have this working again.

Here's my assertion:

The original bulb is a MR11 type, 6v, 5W. The power supply output is 6VAC,
1000ma. How can I make this bulb work? Sorry if this is a naive question.

Thanks.
 
"Mike" <no_spam@comcast.net> wrote in message
news:X8idnZMeg_yVER_cRVn-ig@comcast.com...
Hi folks,

Just a couple of days before halloween, it's important for your light-up
pumpkins and displays to work properly. Unfortunately, one of our displays
blew a bulb the other night and my wife is somewhat upset about it.

So, after going to four stores (two home depots, one lowes, one wal-mart),
nobody had the replacement build. Home depot had a spot for the original
(6v/5w), but both stores were out! So, I picked up at lowes today the
closest match I could find: 12v/20w. Thinking I can just apply some
resistors in-line with the bulb, I figured I could have this working
again.

Here's my assertion:

The original bulb is a MR11 type, 6v, 5W. The power supply output is 6VAC,
1000ma. How can I make this bulb work? Sorry if this is a naive question.

Thanks.
Click to expand...
The original bulb pushes the power supply pretty close. The bulb that you
bought will exceed it a little. If you can change power supplies it would be
your best option.
 
I think I want to keep the same power supply since this unit also has a 6VAC
motor to rotate a colored wheel. The halogen is used to light some
fiberoptics -- pretty neat setup.

I can understand overloading the transformer by using a 12V bulb. But,
wouldn't putting a resistor in series increase the resistance? I guess it
would also make the bulb be dimmer.

Thanks.

"Tom Biasi" <tombiasi@REMOVETHISoptonline.net> wrote in message
news:0wxgd.11329$UC4.6151179@news4.srv.hcvlny.cv.net...
"Mike" <no_spam@comcast.net> wrote in message
news:X8idnZMeg_yVER_cRVn-ig@comcast.com...
Hi folks,

Just a couple of days before halloween, it's important for your light-up
pumpkins and displays to work properly. Unfortunately, one of our
displays
blew a bulb the other night and my wife is somewhat upset about it.

So, after going to four stores (two home depots, one lowes, one
wal-mart),
nobody had the replacement build. Home depot had a spot for the original
(6v/5w), but both stores were out! So, I picked up at lowes today the
closest match I could find: 12v/20w. Thinking I can just apply some
resistors in-line with the bulb, I figured I could have this working
again.

Here's my assertion:

The original bulb is a MR11 type, 6v, 5W. The power supply output is
6VAC,
1000ma. How can I make this bulb work? Sorry if this is a naive
question.

Thanks.

The original bulb pushes the power supply pretty close. The bulb that you
bought will exceed it a little. If you can change power supplies it would
be
your best option.
Click to expand...
 
On Fri, 29 Oct 2004 16:46:15 -0400, Mike wrote:

I think I want to keep the same power supply since this unit also has a
6VAC motor to rotate a colored wheel. The halogen is used to light some
fiberoptics -- pretty neat setup.

I can understand overloading the transformer by using a 12V bulb. But,
wouldn't putting a resistor in series increase the resistance? I guess it
would also make the bulb be dimmer.
Click to expand...
You really need to take an electronics fundamentals course before
any answers to your questions would be meaningful to you.

For your project, get any 6V flashlight bulb. That would be one for
a four-cell flashlight, or any "lantern" that uses a 6V lantern
battery.

Or, stick a flashlight in the pumpkin.

But a 12V bulb will not work from a 6V supply.

Good Luck!
Rich
 
Whether you believe it or not: You cannot power a 12V/20W lamp from a power
suppy that has been made to serve a 6V/5W lamp. But nothing needs to hold
you from trying. You will only end up with no light and a blown power
supply. As you have no skills in electronics the only thing you can do is
looking for lamps <=6V and <=5W. Two 3V lamps in series will do as long as
they are <=2.5W each. Other lamps <6V will need a series resistor and give
you a big problem as you don't know how to calculate its value. Nevertheless
you're welcome to ask again when you found a lamp inside the boundaries I
mentioned.

petrus bitbyter

"Mike" <no_spam@comcast.net> schreef in bericht
news:ncednef05YOLYB_cRVn-iw@comcast.com...
Well, you might be right, but so far nobody has presented a solution to me
that didn't make sense :)

Due to the construction of this display, a flashlight bulb will not work
w/o
serious modification to the display.

Thanks.


"Rich Grise" <rich@example.net> wrote in message
news:pan.2004.10.29.22.48.37.821170@example.net...
On Fri, 29 Oct 2004 16:46:15 -0400, Mike wrote:

I think I want to keep the same power supply since this unit also has a
6VAC motor to rotate a colored wheel. The halogen is used to light some
fiberoptics -- pretty neat setup.

I can understand overloading the transformer by using a 12V bulb. But,
wouldn't putting a resistor in series increase the resistance? I guess
it
would also make the bulb be dimmer.

You really need to take an electronics fundamentals course before
any answers to your questions would be meaningful to you.

For your project, get any 6V flashlight bulb. That would be one for
a four-cell flashlight, or any "lantern" that uses a 6V lantern
battery.

Or, stick a flashlight in the pumpkin.

But a 12V bulb will not work from a 6V supply.

Good Luck!
Rich
Click to expand...

---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.778 / Virus Database: 525 - Release Date: 15-10-2004
 
Thanks for explaining. If I wanted to be really naive and "do it anyways," I
wouldn't have asked the group for their opinion. Anyways, you're wrong. I do
have some skills in electronics -- this just happens to be an area I'm not
too familiar with. Again, you're incorrect about calculating resistor
values.

Actually, I've found the right bulb, so I don't need any more dicatorial
advice from you.


"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:KXLgd.102822$Ye1.90614@amsnews05.chello.com...
Whether you believe it or not: You cannot power a 12V/20W lamp from a
power
suppy that has been made to serve a 6V/5W lamp. But nothing needs to hold
you from trying. You will only end up with no light and a blown power
supply. As you have no skills in electronics the only thing you can do is
looking for lamps <=6V and <=5W. Two 3V lamps in series will do as long
as
they are <=2.5W each. Other lamps <6V will need a series resistor and give
you a big problem as you don't know how to calculate its value.
Nevertheless
you're welcome to ask again when you found a lamp inside the boundaries I
mentioned.

petrus bitbyter

"Mike" <no_spam@comcast.net> schreef in bericht
news:ncednef05YOLYB_cRVn-iw@comcast.com...
Well, you might be right, but so far nobody has presented a solution to
me
that didn't make sense :)

Due to the construction of this display, a flashlight bulb will not work
w/o
serious modification to the display.

Thanks.


"Rich Grise" <rich@example.net> wrote in message
news:pan.2004.10.29.22.48.37.821170@example.net...
On Fri, 29 Oct 2004 16:46:15 -0400, Mike wrote:

I think I want to keep the same power supply since this unit also has
a
6VAC motor to rotate a colored wheel. The halogen is used to light
some
fiberoptics -- pretty neat setup.

I can understand overloading the transformer by using a 12V bulb.
But,
wouldn't putting a resistor in series increase the resistance? I
guess
it
would also make the bulb be dimmer.

You really need to take an electronics fundamentals course before
any answers to your questions would be meaningful to you.

For your project, get any 6V flashlight bulb. That would be one for
a four-cell flashlight, or any "lantern" that uses a 6V lantern
battery.

Or, stick a flashlight in the pumpkin.

But a 12V bulb will not work from a 6V supply.

Good Luck!
Rich





---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.778 / Virus Database: 525 - Release Date: 15-10-2004
Click to expand...
 
On Fri, 29 Oct 2004 14:33:30 -0400, "Mike" <no_spam@comcast.net>
wrote:

Hi folks,

Just a couple of days before halloween, it's important for your light-up
pumpkins and displays to work properly. Unfortunately, one of our displays
blew a bulb the other night and my wife is somewhat upset about it.

So, after going to four stores (two home depots, one lowes, one wal-mart),
nobody had the replacement build. Home depot had a spot for the original
(6v/5w), but both stores were out! So, I picked up at lowes today the
closest match I could find: 12v/20w. Thinking I can just apply some
resistors in-line with the bulb, I figured I could have this working again.

Here's my assertion:

The original bulb is a MR11 type, 6v, 5W. The power supply output is 6VAC,
1000ma. How can I make this bulb work? Sorry if this is a naive question.
Click to expand...
You can't, really.

A 12 volt bulb will be very dim when run on 6 volts.

You could build a voltage doubler to get enough voltage - however,
since your power source is only good for 6 watts, it still won't run a
20 watt lamp.










--
Peter Bennett VE7CEI
email: peterbb4 (at) interchange.ubc.ca
GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html
Newsgroup new user info: http://vancouver-webpages.com/nnq
 
Well, you might be right, but so far nobody has presented a solution to me
that didn't make sense :)

Due to the construction of this display, a flashlight bulb will not work w/o
serious modification to the display.

Thanks.


"Rich Grise" <rich@example.net> wrote in message
news:pan.2004.10.29.22.48.37.821170@example.net...
On Fri, 29 Oct 2004 16:46:15 -0400, Mike wrote:

I think I want to keep the same power supply since this unit also has a
6VAC motor to rotate a colored wheel. The halogen is used to light some
fiberoptics -- pretty neat setup.

I can understand overloading the transformer by using a 12V bulb. But,
wouldn't putting a resistor in series increase the resistance? I guess
it
would also make the bulb be dimmer.

You really need to take an electronics fundamentals course before
any answers to your questions would be meaningful to you.

For your project, get any 6V flashlight bulb. That would be one for
a four-cell flashlight, or any "lantern" that uses a 6V lantern
battery.

Or, stick a flashlight in the pumpkin.

But a 12V bulb will not work from a 6V supply.

Good Luck!
Rich
Click to expand...
 
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