lpdjb@brahms.amd.com (Jerry Bemis) (03/13/91)
I get a bargin price on a UV tube. In measures .3" x 2.5" with a 2.5" base.
It has a 6" zip cord coming out the end of the base.
glase tube
| ______________
/----------- base |====== cord
\-----------______________|
Now I need to know how to light it. 120 volt AC doesn't light it up.larry@kitty.UUCP (Larry Lippman) (03/13/91)
In article <1991Mar12.214815.11808@amd.com> lpdjb@brahms.amd.com (Jerry Bemis) writes: >I get a bargin price on a UV tube. In measures .3" x 2.5" with a 2.5" base. >It has a 6" zip cord coming out the end of the base. > > glass tube > | ______________ >/----------- base |====== cord >\-----------______________| > >Now I need to know how to light it. 120 volt AC doesn't light it up. This is pure speculation on my part, but it sounds like you have a pencil-type UV lamp manufactured by Ultraviolet Products, Inc. that is in their model series called "Pen-Ray". A Pen-Ray lamp is a medium pressure mercury lamp which requires a high voltage for starting, with a low voltage through a ballast for continuous operation. While I have seen and used Pen-Ray lamps, I don't know the exact design of the Pen-Ray ballast circuit. They may use what is called an "iso-stabilized constant wattage ballast", which resembles a transformer. The primary goes to the 120 volt AC line, and the secondary connects to the lamp in series with a capacitor. Open-circuit voltage (i.e., lamp not fired) may be 300 to 700 volts, depending upon lamp size. Voltage across the lamp may drop as much as by a factor of 10 while the lamp is in operation. Assuming that I am correct for your particular lamp, the problem is that the above ballast is not a simple two-winding transformer. It is specially designed with particular saturation losses at given secondary currents. Offhand, I can't think of a simple and cost-effective way to duplicate the required ballast circuit. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 [note: ub=acsu.buffalo.edu] uunet!/ \aerion!larry
tomb@hplsla.HP.COM (Tom Bruhns) (03/14/91)
lpdjb@brahms.amd.com (Jerry Bemis) writes: >I get a bargin price on a UV tube. In measures .3" x 2.5" with a 2.5" base. >It has a 6" zip cord coming out the end of the base. > > glase tube > | ______________ >/----------- base |====== cord >\-----------______________| > > >Now I need to know how to light it. 120 volt AC doesn't light it up. >---------- You're lucky the 120VAC didn't light it! At least, I assume this is like the ones I used in a project a number of years ago. Once you get it turned on, the voltage will drop significantly, and the dynamic impedance will be vveeeerry low. So if 120V had lit it, it would have drawn enough current to destroy itself (assuming you didn't have any current limiting). As I recall with the ones I was using--very nearly the same size-- it took 500 to 1000 volts to get them started, then a couple hundred to keep them going. I believe the standard power supplies for them are built like a scaled-down neon tube transformer. It's possible to accomplish about the same thing at the expense of some power dissipation by putting a reactance (inductor or capacitor) or even resistance in series with a high-voltage AC supply. (The application I worked on required modulating the light intensity, so we used a DC bias current with superimposed AC at the desired amplitude/phase/frequency; was used to cause electron emission from a metallic surface, to check for surface cleanliness...)