Laser Hobbyists - Hobby Archives

DISCLAIMER:
This is a REPORT of the further work done on this project. For information purposes ONLY!
This was done for our OWN edification and should NOT be construed to be a plan, kit, or endorsement of this device or the methods contained within. NO claim is made for applicability, or SAFETY.!!!!! Use at YOUR own RISK !!!!

WARNINGS:
Do NOT attempt this project without knowledge of safe wiring practices!
BURN HAZARD!!!! High temperatures are involved!
This design has been developed and tested with White Mineral Oil ONLY!!!

The changes presented reflect the revised design as of May, 1999. The hazer was demonstrated, and warmly received, at Laser F/X'98: The Lightshow Conference 16-18 May,1998. (I figured it was about time to write up the report!)
This design was developed by experimental methods and should NOT be construed to be a final design, or, the BEST. It DOES work in my basement AND it started hazing the upstairs too! (And had an admiral showing at the Laser F/X'98 open house).

The haze stays suspended, at a usable level, for approximately an hour, or so, after the unit is shut down. The heater element is switched separately so the fan can continue to run, cooling the unit after use. Since sufficient heat is generated, with the heater enclosed and insulated, a successful test was done returning to the original "blowing fan" design below.

The 12in. extension to the hazer's output helps "collimate" and direct the flow and increases the dispersion speed throughout the room.

In the original arrangement of the hazer, maximum temperature/haze output was achieved after one hour of heating. This slow start-up is a side-effect of using the heater at 30V instead of it's designed 110V. Addressing the hazer's slow warm-up, a DPDT relay was added to dump full line current into the heater element to reach operating temperature faster ("Quick-Start"). A self-contained timer-relay was used, instead of a separate relay/control circuit, for ease of assembly. A "full power" boost of only 30-40 seconds is sufficient to begin haze generation.

The heater element is a monolithic aluminium cast unit, [see photo below] as used in "Party-Perk" type coffee makers.

The heater is filled to the mould mark on the inside, which is at the same height as the element winding, in the bulge, around the outside.

    In the current test-bed, the heater is enclosed and packed in fiber insulation, achieving approximately 525 F as opposed to 400 F when un-enclosed. The heater draw at 30V is approximately 1.5A.
    A second unit has been built for a local laserist. We both attempted to use "laxitive" weight mineral oil without success. This "heavy" weight oil did form haze, with difficulty, but at a higher temperature and a VERY narrow operating range.
    The "Quick Start" boost time was extended to raise the temperature and start hazing. After a period of running, the haze diminished as the heater leveled to temperature, running off the transformer that worked with the lightweight oil. Re-starting the boost cycle only managed to "boil" off the oil, at a high rate, developing unacceptable odor.

A) The "Party-Perk" heater element is 110VAC. In it's intended use, however, it is designed to sink to ~3 Gallons of water. I *have* turned one of these on on, removed from a pot, and it DID MELT!!!!!!. This previous experience led to the use of the "ballast" transformer in the heater circuit. The 30V transformer will allow the heater to reach only 400-550 F, depending on the enclosure/insulation design.

B) The "flash point" of mineral Oil is 444 F, open cup test, per Sax's Dangerous Properties of Industrial Materials. This is the second criteria for limiting the heater's maximum temperature. A flashpoint is the temperature at which a substance will ignite IN THE PRESENCE OF AN IGNITION SOURCE. In the design, as currently operating, the mineral oil, IN THE HEATER, is at ~525 F to generate the airborne vapor, which condenses to form the haze.

The air blown through the generating chamber cools the smoke/air combination, immediately above the heater, to ~80 F, well below the flash-point of mineral oil (by thermocouple measurement in a 68 F room).

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