Fabricating a Heater for the Fishtank

ENGR 121

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22-gage solid core wire40-inch length

Parts

20Ω Power Film ResistorDigikey MP915-20.0F-ND or Caddock Electronics TO-126

3/8” polyolefin heat shrink tubing (3:1 shrinkage ratio)6-inch length

3/32” polyolefin heat shrink tubing (2:1 shrinkage ratio)two 5/8-inch lengths

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Tools and Supplies

Safety

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1. Wear safety glasses.2. Soldering involves high temperatures. Be careful not to touch hot surfaces, including . . .

a. The tip of the soldering ironb. The soldering iron holderc. Anything that is touches with the soldering iron (what you are soldering)

3. Soldering can be a fire hazard.a. Don’t solder around flammable substances.b. Don’t walk away from a soldering iron that is turned on.c. Be aware of the location of the fire extinguisher.

4. The materials used in soldering may contain lead or other toxins. Solder in a well ventilated space, and try to avoid breathing fumes.

5. Be aware of others around you when you are soldering, and alert them to any potential hazards (hot surfaces, fumes).

6. If you are burned, please alert your instructor. Be aware of the location of the first aid kit.

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Cut and Strip Wire

Cut a 40-inch length of wire, and strip about ¼-inch of insulation off each end.

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Apply Flux and Tin Wire and Resistor Terminals

flux applied to resistor terminals

resistor after tinning

wire after tinning

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Solder Wire to Resistor

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Use Heat Gun on Heat Shrink

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Use Drill to Twist Wire

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Install 3/8-inch Heat Shrink (insert resistor about ½-inch up into the end of the heat shrink)

heat tip last so it will be hot for sealing

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Seal the Open End of Heater(clamp in vise for about 15 seconds with low to medium clamping force)

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Using the HeaterThe heater MUST be immersed in water any time it is turned on; the resistor will become very hot and burn out in about a minute otherwise.

There could be a fire hazard if the heater is turned on in the vicinity of flammable substances.

Be sure to leave your entire system unplugged from the wall outlet unless you are actively working on it.

It would be a good idea to keep the heater unplugged unless you are using the system to control temperature.

NOTE: The resistor used here was not designed to be used as a heater. The use of this heater should be limited to students participating in the Living with the Lab curriculum for the specific purpose of heating the water for the fishtank project.