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Vistalight nightsticks
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 -- |
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#2
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Vistalight nightsticks
On Tue, 29 Jun 2004 06:10:53 +1000, "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? 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. |
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Vistalight nightsticks
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. |
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Vistalight nightsticks
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 +-----------------------------------------------------------------+ | This message has been sent to you using recycled electrons | | exclusively. Please do not discard them after use, | | send them along and help conserve these irreplaceable | | sub-atomic resources for future generations. | +-----------------------------------------------------------------+ I was on vacation, traveling in France and England throughout most of the month of June. Due to the SPAM and Virus problem, I typically get about 4,000 emails daily. Usually my filters are able to deal with the flood, but while I was overseas, I wasn't able to get Internet access as often as I would have liked. As a result, my mailbox got choked up on two occasions, causing the loss of about 190 mb of mail (tens of thousands of messages) each time. If you mailed me and didn't get an answer, please re-send your message. Harris Cyclery, West Newton, Massachusetts Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide http://captainbike.com http://sheldonbrown.com |
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Vistalight nightsticks
"G. Huang" wrote in message ... 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. |
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Vistalight nightsticks
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] |
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Vistalight nightsticks
On Tue, 29 Jun 2004 19:27:58 +1000, "Justin Vincent"
wrote: 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. |
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