Introduction: Turn Up for Resistance

Picture of Turn Up for Resistance

The following information is a single lesson in a larger project. Find more great projects here.

Return to Previous Lesson: See the Rainbow with the RGB LED

Lesson Overview:

Now we'll learn about electrical resistance!

Step 1: Introduction

Picture of Introduction

In this lesson you’ll learn about a new component: the potentiometer.

A potentiometer is a variable resistor. Notice the component module that is already in the Workplane: it has three terminals. Turning the knob adjusts the amount of resistance between the “wiper” and each of the other terminals (feet 1 and 2).

You can use the potentiometer to fade an LED on and off or to change the volume of the buzzer.

In fact, any device that you have at home with a knob on it probably uses a potentiometer! The volume knob on a stereo or temperature setting knob on a thermostat are a good examples.

  1. Press the "next" button below to continue.

Step 2: Connecting the Circuit

Picture of Connecting the Circuit

Use the conductive ink pen to wire up the circuit and see how the potentiometer works.

  1. Select the Conductive Pen.
  2. Connect the positive terminal of the battery to the Potentiometer wiper (the top terminal).
  3. Connect Terminal 1 (left) of the potentiometer to the top terminal of the first LED.
  4. Connect Terminal 2 (right) of the potentiometer to the top terminal of the second LED.
  5. Connect the negative terminal of the battery to the bottom terminals of both LEDs.
  6. Press the "next" button below to continue.

Step 3: Simulating the Circuit

Try simulating the circuit and turning the potentiometer knob!

  1. Click the Start simulation button.
  2. Move the potentiometer knob by clicking on it and moving the cursor around the perimeter of the knob.
  3. What happens to each LED as you turn the knob?
  4. Press the "next" button below to continue.

Step 4: Understanding the Potentiometer

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As you turn the potentiometer, one LED becomes brighter, and one becomes dimmer. Here’s what happens as you twist the knob:

CLOCKWISE: the resistance between wiper and terminal 1 is the highest it can be: 10,000 ohms.

The resistance between the wiper and terminal 2 is very low -- almost zero ohms.

In the MIDDLE: both branches have the same resistance: 5000 ohms. Notice that the sum adds up to 10,000. This is always true regardless of the position of the knob.

COUNTER-clockwise: This is simply the opposite of the first case (turning clockwise).

The resistance between the wiper and terminal 2 is the highest it can be: 10,000 ohms.

  1. Try turning the knob all the way to the left. What happens?
  2. Try orienting the knob in the center, pointed at the wiper.
  3. Finally, try turning the knob all the way to the right.
  4. Press the "next" button below to continue.

Step 5: Printing Out the Circuit

To wrap up this lesson, try printing out your potentiometer circuit template and placing modules from your Circuit Scribe kit.

After printing out and filling in your circuit, try turning the potentiometer knob back and forth: you can feel a slight click when it passes through the middle point. This indicates that the knob is pointed towards the wiper and that the resistance to either side is equal.

  1. Click the download PDF button in the simulator
  2. Save the PDF to your computer. Print out this PDF, fill in the dotted lines and try out your circuit!
  3. See what happens as you twist the potentiometer knob back and forth.
  4. Press the "next" button below to continue.

Step 6: Making a Color Blender

Picture of Making a Color Blender

In this part of the lesson, you’ll replace the two LEDs with an RGB LED to make a custom color blender. When you turn the potentiometer knob, the LED will transition from one color to another.

Try following the instructions below to complete the circuit - the solution will be shown in the next step.

  1. Stop the simulation.
  2. Start modifying the circuit by deleting the two LEDs, their pad footprints, and the lines connecting them to the rest of the circuit.
  3. Open the Modules + tab and drag an RGB LED into the Workplane. Place it below the potentiometer.
  4. Next, use the Conductive Pen to connect the negative (-) terminal of the battery to the bottom, ground terminal of the RGB LED.
  5. Finally, connect the two bottom terminals (1 and 2) of the potentiometer to different terminals on the top of the RGB LED. For example, terminal 1 connected to RED and terminal 2 connected to BLUE.
  6. Press the "next" button below to continue.

Step 7: Blending the Colors

Picture of Blending the Colors

Check your circuit with the example we show below to make sure you have it wired up correctly. Then simulate your circuit! What happens as you turn the potentiometer knob?

In the time that you have remaining, try connecting up different colors to the poteniometer.

Can you think of any examples where potentiometers or RGB LEDs are used in real life?

There are only two lessons left before the final project! In the next lesson you will learn about a new type of component: a light sensor.

  1. Simulate the circuit.
  2. In your remaining time, try connecting different terminals of the RGB LED to the potentiometer to blend different colors together!

Next Lesson:Shedding Some Light on Things

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