Tutorial 2. Introduction to moway robot Electronics www.moway-robot.com 1
Index Introduction... 2 Basic concepts of electronics... 3 Hydraulic circuit... 3 Electrical circuit... 5 www.moway-robot.com 1
Introduction Before starting to explain the devices that forms the moway robot, let s learn some basic concepts of electronics. This is necessary in order to understand how the robot sensors work, that is, how moway can stop when it reaches an obstacle, turn on its light when it passes through a tunnel and many other actions. The first image is the electronic board which is inside the moway robot. The other two images show different electronic devices (microprocessors, capacitors, LEDs, etc.). As you have already seen, the robot is formed by several electronic devices. These devices are connected each other by different electronic circuits. Let s start step by step, by explaining some basic concepts of electronics. www.moway-robot.com 2
Basic concepts of electronics There are three basic concepts in electronics: Voltage Current Resistance Sometimes it is difficult to see how electricity works. In order to understand these concepts easily, let s compare an electrical circuit with a hydraulic circuit: for example, a pipe through which water flows. Hydraulic circuit The hydraulic circuit consists of the following components: A tank with water, at a certain height. A sloped pipe Tank Pipe Ground As the tank is placed at a certain height, the gravity force makes the water to flow from the tank down through the pipe. Let s see three different cases in which, depending on the tank height, the amount of water through the pipe is different. www.moway-robot.com 3
If the tank were at ground level, the water couldn t flow through the pipe. However, if the tank is placed at a certain height, the water will flow down through the pipe. The greater the height of the tank is, the greater amount of water will flow through the pipe. Summary: High tank Low tank Tank Pipe A lot of water Little water As we have seen, depending on the tank height the amount of water that will flow through the pipe will be different. Now let s compare this with an electronic circuit, in which the tank height will be the voltage and the amount of water will be the electric current. www.moway-robot.com 4
Electrical circuit In an electrical circuit, there is an electric wire instead of a pipe, and there is an electric current instead of water. In addition, in the hydraulic circuit example the tank provided water. In the case of the electronic circuit a battery provides the electric current. Battery Wire Light bulb When the wires are connected to the battery an electric current starts to flow through the wire. When this current passes through the light bulb it turns on. If the battery voltage is low the current will also be low, and then the light will be soft. In the following images we can see the representation of the electrical circuit (on the left, low voltage) and the equivalent of the hydraulic circuit (on the right, low tank). Low current Low voltage www.moway-robot.com 5
The higher the battery voltage is, the higher will be the current through the wire and the light will be more intense. High current High voltage As we have seen, the voltage is like it set the sloping of the pipe. The current is like it was the amount of water. This means that the greater the sloping (voltage) is, the greater the amount of water (current) is. Comparative: Hydraulic circuit Electrical circuit Pipe Electric wire Water tank Battery Tank height Voltage www.moway-robot.com 6
Amount of water Current Now imagine that there are stones or other objects inside the pipe. In this case it is difficult for the water to flow, so that the amount of water through the pipe will be less. In an electrical circuit, a device that offers resistance to current flow is called resistor. In an electric diagram a resistor is depicted as a zigzag line, as it is shown on the next image. Hydraulic circuit Electrical circuit Obstacles Resistor www.moway-robot.com 7
If we used the same battery (that is to say, the voltage doesn t change), if the resistance is high, the current through the circuit will be low (the higher the resistance is, the more difficult is for the current to flow). So that, the light is weak. High resistance Low current However, if the resistance is low, the current will be high (the current will flow more easily). So that, the light will be intense. Low resistance High current Summary: We have seen that the current that flows through an electrical circuit will depend on the resistance of that circuit. So that: If the circuit has a high resistance, the current will be low. If the circuit has a low resistance, the current will be high. www.moway-robot.com 8
Question: How can moway detect the environment variables (temperature, brightness,...) taking advantage of what has been explained previously? Answer: moway robot can measure the room temperature, the light that it receives, the level of its battery, etc., by means of its internal sensors. A sensor is an electronic device that allows to measure the environment variables, such as temperature, brightness, noise, etc. A sensor has a certain electric resistance. This resistance varies depending on the environment. As we have seen before, when the resistance varies, the current through the circuit also varies. This current can be measured by moway, by means of its microprocessor (the brain of moway). For example, the resistance of the moway light sensor decreases when the environmental light is intense. Light sensor When the resistance of the light sensor is low, the current through the circuit is high. The microprocessor of moway measures this current and this way it knows that the environment light is intense. The next image shows the case in which the environmental light is intense: Intense light High current Low sensor resistance Battery Microprocessor www.moway-robot.com 9
In this case, the image shows the case in which the environmental light is weak: Weak light Low current High sensor resistance Battery Microprocessor Summary: Environment Sensor Circuit Intense light Low resistance High current Weak light High resistance Low current We also have sensors in our body: We feel the temperature in our skin (temperature sensor) We can see if there is light with our eyes (light sensors). etc. EXERCISE: You can think about other sensors that human beings have in order to get information about the environment that surrounds us. www.moway-robot.com 10