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Modified 10/05/06 This schematic and source code areintended for demonstration purposes only. They are offered "as-is". Use at your own risk. Proper and sufficient fail-safes and thermostats must be used and sized to the particular installation and usage! Code and circuits (and more) are here. IntroductionThis program is a steam generator controller that is intended for use in a residential steam shower. It controls water inlet and drain valves, power to the heating element, and various level and thermal sensors. FeaturesPush button automated control of the steam shower. High and low steam rates, extendable cycles, error conditions are sensed and handled. Specifications
ConstructionThis project works quite well but has not passed the prototype stage yet. (It's still built on a wooden platform!) The tank is a 4" copper pipe with end caps. It is silver soldered to withstand heat. The replacable 3000W heating element extends inward through one end of the tank. Stainless bolts are used. The relay card is a pre-existing unit that I had in my collection. The 220/24V transformer, solid state relay, cooling fan are below the relay card. The "U" shaped 1/4" flexible copper tubing alongside the tank is for preheating the incoming water so that it doesn't squelch the steam when the inlet water valve opens. ![]() Click on photo to display full size version. The microcontroller board is really quite simple. The water level switch comes on on the black/red wires. Other connectors exist for the 5V cooling fan, solid state relay, and thermal sensor. Control panel comes in on the green cable and RJ-45 connector. The relay board is connected via flat ribbon cable. The ICSP PIC programming port is at the lower left. ![]() ![]() The tank level switch is is mounted in an assembly that can be removed. The capped copper pipe in the forground will eventually get an over-pressure safety valve. ![]() Click on photo to display full size version. The two water valves are for inlet and drain. They have a 5/8" orifice opening, which is really much larger than necessary for the water inlet, which is significantly throttled down by a petcock in the water supply. The drain valve (at bottom of the photo) should be capable of withstanding water that is 80-100C. It drains by gravity (into the white PVC in the photo) so the 5/8" orifice opening is helpful. The 3000W heating element connection is seen at the righthand end of the copper tank. ![]() Click on photo to display full size version. The control panel is simply two push button switches mounted on a standard blank switch plate. ![]() Click on photo to display full size version. There are two bright white LEDs that are visible through the ivory colored switch plate, as well as an RJ-45 jack and piezo beeper mounted behind the panel. ![]() Click on photo to display full size version. OperationNormal operation
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