Core Project: Activity Three

Hands On Physics

Haze
Core Project
Preparing the Wires, Switch, & LED

Overview:

This activity continues the construction of the sun photometer.

See tools and materials for a complete list of the parts required.

Prepare the Wires

You will need 8 lengths of #20AWG solid connection wire. You can use one color, but it's less confusing to use 2 colors.

Cut these lengths of wire:

8 cm wires: 2 red and 1 black
10 cm wires: 1 red and 2 black
11 cm wires: 1 red and 1 black
1. Next, remove about 5 mm of insulation from both ends of the two 8-cm wires.
2. Then, remove about 5 mm of insulation from only one end of each of the remaining wires.
3. Finally, remove about 12-15 mm of wire from the second end of the remaining wires.
4. Check the wires to make sure you have cut and trimmed them properly.

Prepare the Switch

Now attach 4 of the wires to the screw terminals on the switch.

Use a cross-point screwdriver to loosen the 2 center screws and 2 of the screws on one side of the switch. You can select either side. Do not loosen the screws on the remaining side.
Find these 4 wires which you previously prepared: (10 cm red; 10 cm black; 11 cm red; and 11 cm black) Form a u-shaped hook in the exposed 12-15 mm end of each wire as shown in Fig. C4 (see "wire + screw"). The easiest way to do this is to wrap the wire around a nail or thin screw driver blade.
Refer to Fig. C4 and attach the wires to the 4 terminals. The bend in the hooks of each wire should be oriented in the same direction the screws are tightened (clockwise). Tighten each screw after placing a wire around it.

Prepare the Light Detector

The TERC VHS-1 Sun Photometer uses a light-emitting diode (LED) as a light detector. You must remove the rounded, lens-like end of the LED (Fig. C1) to simplify aiming the instrument at the Sun.

Place a piece of coarse 40 or 60 grit sandpaper on a flat surface. Hold the LED by its sides and rub the end of the LED back and forth or in a circular pattern against the sandpaper until the entire rounded section has been removed.
Now hold the LED as vertical as possible and rub the sanded end of the LED in a circular pattern until the end of the LED is perfectly flat and level.
Wipe away any plastic dust from the end of the LED. Set the LED aside in a safe place until it's ready to install.