Vistalight nightsticks

Justin Vincent

I recently bought a second hand (but not very old)
nightstick set. Knowing that a replacement globe (rated at
6V, 12W will cost me at least A$25 I headed to my local
hardware store & found one (rated at 12V, 20W) that fits
for $4.50.

My knowledge of physics (P = V squared / R) tells me that
using it with the a 6V battery it will run at 5W. (Other
higher wattages were also available!)

Is there any reason why this wouldn't be a suitable
alternative?

(Also, in the process of replacing the globe I discovered
that one of the contacts that the globe sits on is held in
place by a weak solder. This broke off, requiring the
switch to be removed & the contact resoldered. Not an
impossible repair, but not something that an average user
would want to do!!)

Justin Vincent

--

Werehatrack

On Tue, 29 Jun 2004 06:10:53 +1000, "Justin Vincent"
<justin_vincent@hotmail.com.au> wrote:

>I recently bought a second hand (but not very old)
>nightstick set. Knowing that a replacement globe (rated at
>6V, 12W will cost me at least A$25 I headed to my local
>hardware store & found one (rated at 12V, 20W) that fits
>for $4.50.
>
>My knowledge of physics (P = V squared / R) tells me that
>using it with the a 6V battery it will run at 5W. (Other
>higher wattages were also available!)
>
>Is there any reason why this wouldn't be a suitable
>alternative?

A 12V bulb operated at 6V will, in my experience, produce
far less than the light output obtained by using it at its
rated voltage, perhaps as little as one tenth of the
expected brilliance. It is not the case that the light
output scales with the power used.

Also, if the housing is designed to dissipate only the heat
from a 12W bulb, the 15W unit might produce enough to damage
it, though I think that's probably not enough of a boost to
be a matter for serious worries.

>(Also, in the process of replacing the globe I discovered
>that one of the contacts that the globe sits on is held in
>place by a weak solder. This broke off, requiring the
>switch to be removed & the contact resoldered. Not an
>impossible repair, but not something that an average user
>would want to do!!)

To use the units at 12 volts, build a 12V battery pack. You
may find that it is possible to replace the NiMH cells in
the existing pack with units half the length but of the
same per-cell voltage, and keep the physical form factor of
the current setup. You'll need a different charger in that
case, though.
--
Typoes are a feature, not a bug. Some gardening required to
reply via email. Surrealism is a pectinated ranzel.

G. Huang

Justin Vincent wrote:

> I recently bought a second hand (but not very old)
> nightstick set. Knowing that a replacement globe (rated at
> 6V, 12W will cost me at least A$25 I headed to my local
> hardware store & found one (rated at 12V, 20W) that fits
> for $4.50.
>
> My knowledge of physics (P = V squared / R) tells me that
> using it with the a 6V battery it will run at 5W. (Other
> higher wattages were also available!)
>
> Is there any reason why this wouldn't be a suitable
> alternative?
>

Physics also says that the wavelengths of thermo radiation
increase as the temperature drops. When you run the bulb at
below the voltage it is designed for, the temperature of the
filament does not reach the point where it can produces
significant amount of VISIBLE light - efficiency goes down
drastically. Most of the radiation will be in infrared which
will not help you.

Sheldon Brown

Justin Vincent wrote:

> I recently bought a second hand (but not very old)
> nightstick set. Knowing that a replacement globe (rated at
> 6V, 12W will cost me at least A$25 I headed to my local
> hardware store & found one (rated at 12V, 20W) that fits
> for $4.50.
>
> My knowledge of physics (P = V squared / R) tells me that
> using it with the a 6V battery it will run at 5W. (Other
> higher wattages were also available!)
>
> Is there any reason why this wouldn't be a suitable
> alternative?

Yes. See the nomograph at
http://www.carleylamps.com/tables.htm

With half the voltage, the lamp will draw .68 as much
current. P = v X a, so it should draw 4.08 watts (6v X .68
a)

However the light output will only be a tenth of the
designed output, and will be a very low (yellow/orange)
colour temperature.

The good news is that the bulb will last virtually forever
under these conditions.

Sheldon "Electrons" Brown +--------------------------------------------------------
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Justin Vincent

"G. Huang" <gang@removethis_bell-labs.com> wrote in message
news:cbq61i$id0@netnews.proxy.lucent.com...
> Justin Vincent wrote:
>
> > I recently bought a second hand (but not very old)
> > nightstick set.
Knowing
> > that a replacement globe (rated at 6V, 12W will cost me
> > at least A$25 I headed to my local hardware store &
> > found one (rated at 12V, 20W) that
fits
> > for $4.50.
> >
> > My knowledge of physics (P = V squared / R) tells me
> > that using it with
the
> > a 6V battery it will run at 5W. (Other higher wattages
> > were also
available!)
> >
> > Is there any reason why this wouldn't be a suitable
> > alternative?
> >
>
> Physics also says that the wavelengths of thermo radiation
> increase as the temperature drops. When you run the bulb
> at below the voltage it is designed for, the temperature
> of the filament does not reach the point where it can
> produces significant amount of VISIBLE light - efficiency
> goes down drastically. Most of the radiation will be in
> infrared which will not help you.
>
> Well, you can't argue with physics! I guess trying a
> higher rated 12V 40W
globe still wouldn't be the same either.

Frank Krygowski

Justin Vincent wrote:

> I recently bought a second hand (but not very old)
> nightstick set. Knowing that a replacement globe (rated at
> 6V, 12W will cost me at least A$25 I headed to my local
> hardware store & found one (rated at 12V, 20W) that fits
> for $4.50.
>
> My knowledge of physics (P = V squared / R) tells me that
> using it with the a 6V battery it will run at 5W. (Other
> higher wattages were also available!)
>
> Is there any reason why this wouldn't be a suitable
> alternative?

It won't work at all. You need a six volt bulb.

Reflectalite has the six volt MR-11 bulbs for a bit less. I
didn't check shipping costs, though.

I've dealt with them on other items, and the service was
good.

http://www.reflectalite.com/halogenpage.html

--
Frank Krygowski [To reply, remove rodent and vegetable dot
com. Substitute cc dot ysu dot edu]