Hobbyist's Hazer Revisited
This page was contributed by Mark Schweter firstname.lastname@example.org
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!)
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) 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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