Dimmer Box




Introduction: Dimmer Box

About: I'm an Engineer. I like hiking, flea markets, and electronics.

The following instructable shows how to make a dimmer box with the following features:

  • Scale for repeatable setting.
  • On / off switch.
  • Dimmer override switch.
  • Over-current protection fuse.
  • Non-conductive wooden case.

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Step 1: Circuit

In the United States, the electricity that's available in most homes is single-phase. It comes to homes through a transformer, where the secondary winding is center-tapped. There are typically 3 thick wires coming into a home, they provide the following voltages:

  • Hot 1: One tap of the the transformer secondary winding, considered 120 volts AC.
  • Neutral: The center-tap of the transformer secondary winding, consider 0 volts AC.
  • Hot 2: The other tap of the transformer secondary winding, considered 120 volts AC, opposite polarity as Hot 1.

If you measure the voltage between any Hot and Neutral, it will measure 120 volts AC. Because of the polarity between Hot 1 and Hot 2, the measured voltage between them is 240 volts AC.

At the circuit breaker box, the wires get distributed as follows:

  • Red: Hot 1
  • Black: Hot 2
  • White: Neutral
  • Green: Ground, which connects to Neutral and a metal rod buried in the ground.

Even though Neutral and Ground are electrically identical, they cannot (legally) be used the same:

  • Neutral: Provides a return path for Hot 1 and/or Hot 2.
  • Ground: Provides an alternate path for Hot 1 or Hot 2 in case of malfunction.

For example, a ground fault interrupt (GFI), the funny looking outlet with a "test" and "reset" button, checks to see if anything is going to Ground and disconnects Hot from the outlet if enough current flows to Ground.

Except for heavy duty outlets, which provide both Hot 1 and Hot 2 to supply 240 volts AC, most other outlets in a home distribute 120 volts AC by supplying the following wires:

  • Hot: This can be either Hot 1 or Hot 2, this is the "small" slot on the right side of the outlet.
  • Neutral: This is the "large" slot on the left side of the outlet.
  • Ground: This is the round semi-circle hole at the bottom of the outlet.

If you are comfortable using a multimeter, then a house with correct wiring should show the following:

  • Hot to Neutral Voltage: 120 volts AC.
  • Hot to Ground Voltage: 120 volts AC (assuming GFI doesn't trigger).
  • Neutral to Ground: 0 volts AC.

Because of the above requirements, the circuit has the following features:

  1. There is a fuse immediately after the Hot input, because if anything goes wrong, the fuse should blow. This happens before the switches and dimmers, in case the switchers or dimmers are at fault.
  2. There is a switch after the fuse which provides "On and Off" capability.
  3. There is a dimmer after the "On and Off" switch so that power can be adjusted.
  4. There is another switch connected to bypass the dimmer when "On".

Possibly the only "safety" issue I'm aware of in the dimmer could heat up after a long use period, though I'm not a certified electrician and the safety of this circuit is your responsibility, should you choose to assemble it.

Step 2: Dial Face

In this step, drill the center of the dial-face after marking a corner-to-corner X in a square piece of wood 5 and 1/2 inches by 5 and 1/2 inches by 1/4 inch thick.

Step 3: Switches and Outlets

In this step, you'll need to mark up 3 sides of the box for switches and outlets:

  1. For sides, make a corner-to-corner X with a line down the middle.
  2. For two sides, use an existing switch plate to trace its holes.
  3. For one side, use an existing outlet plate to trace its holes.

The height of the sides should be sufficient to hold the dimmer, switches, and an outlet.

Step 4: Cutouts

In this step, take the 3 sides that have have been traced and remove the cut-out areas so that the switches and outlet fit. Finally, drill out the screw holes, making sure not to go through the wood completely. For the 4th side, include a hole for the fuse and input wire.

Step 5: Check Dimmer

In this step, determine the center line for your dimmer:

  1. Rotate the dimmer completely counter-clockwise. Mark where the horizontal notch faces.
  2. Rotate the dimmer completely clockwise, Mark where the horizontal notch faces.
  3. Provide a line between the two notches, going through the center of the switch.
  4. Make sure that the center line, between the two notches lines up with the center of your dial-plate.

Step 6: Glue

In this step, glue the switch and outlet plates to the dial plate.

Step 7: Pointer

In this step, create a pointer for the dial. A sawed-off screw can be used to hold the dial in place from the side.

Step 8: Back-Plate

After the wood has dried, place the back-plate onto the box and create 4 drill holes on each side, about 1/8 from the center. The holes should be recessed. Masking tape may be used the hold the back-plate in place while drilling.

Step 9: Dial

In this step, create the dial circle:

  1. Secure the dimmer onto the dial-plate using a earthquake / mounting putty.
  2. Drill a popsicle stick so that that it can be used as a template form circle on the dial.
  3. Mark the limits of the dimmer.
  4. Use a protractor to split the usable circumference into 10 sections.

Step 10: Mark and Finish

In this step, mark and finish the pieces:

  1. Number the dial from.
  2. Label one of the switches with On and Off.
  3. Label the other switch with Dim and Full.
  4. Finish the wood with polyurethane.
  5. When dry, apply a coat of paste wax.

Step 11: Prep

In this step, prepare the switches and outlet:

  1. Attach wires to switches and outlet.
  2. Insulate bare metal with electrical tape.
  3. Use contact cement to attach any washers that would be needed between switches and outlet or wood.

Step 12: Screw and Wire

In this step, screw everything into place. The use of a side screwdriver may be necessary. Use twist-on wire connectors to join the wiring.

Step 13: Finish

Finally, add screw in the rear-plate and you're ready to use!

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    3 years ago

    Excellent Instructable! Good project, excellent write up with theory and directions, and great-looking final product!