Vistalight nightsticks

Justin Vincent said:

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.

Quoted message said:

(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.

Justin Vincent said:

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.

Justin Vincent said:

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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"G. Huang" <gang@removethis_bell-labs.com> wrote in message
news:[email hidden]...

Quoted message said:

Justin Vincent said:

I recently bought a second hand (but not very old) nightstick set.

Knowing

Quoted message said:

Quoted message said:

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

Quoted message said:

Quoted message said:

for $4.50.

My knowledge of physics (P = V squared / R) tells me that using it with

the

Quoted message said:

Quoted message said:

a 6V battery it will run at 5W. (Other higher wattages were also

available!)

Quoted message said:

Quoted message said:

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.

Justin Vincent said:

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]

Justin Vincent said:

Well, you can't argue with physics! I guess trying a higher rated 12V 40W
globe still wouldn't be the same either.

No. It would probably just generate enough heat to melt the housing
without providing enough illumination to see much. Bulbs are not like
diodes, SCRs, etc, where a higher-rated unit can be pretty freely used
as a replacement for a lower-rated one. With bulbs, the voltage spec
is critical.

--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Surrealism is a pectinated ranzel.