Thursday, February 12, 2015

#4 - Introduction to Switches, Relays, and VEX Robotics (Inventory and Construction)

Switches and Relays

Now lets cover some key components for the course (and electronics in general): switches and relays. We will begin with switches as relays are a more advanced version of a switch. Switches are basically components used for toggling on/off portions of the circuit, by closing (or opening, depending on the switch) the circuit when pressed, and doing the opposite when released. There are many forms of switches: SPST (single-pole-single-throw), SPDT (single-pole-double-throw), DPDT (double-pole-double-throw), etc. A relay is a more advanced type of switch that uses a component called an inductor along with a type of switch mentioned above. When current flows through the inductor, it creates a magnetic field, which in turn attracts the switch, thus pulling it into a new position, toggling the state of the switch as long as the current holds. Below are pictures of a relay in use (the orange box).
When the switch is not pressed, the top LED lights up.

However, when pressed, the switch causes current to flow, thus creating a magnetic field in the inductor, and toggling the state of the relay. Now the bottom LED is lit.


Now for a variant. By adding a capacitor, we can make a oscillator.



Relay Oscillator: A variant of the previous circuit. When the switch is pressed, the magnetic field's induced voltage in tandem with the capacitor causes the state of the relay to oscillate-meaning that it toggles states at high frequency; thus alternating between which LED is lit quite frequently. One of the LEDs appears brighter because it is turning on more often than the other.

VEX

What this course will work up towards is the use of robotics. VEX is a brand of robotics products that aims at teaching the basics and advanced skills. Before we can begin building however, we needed to stop and first inventory a large portion of the parts (just to make sure we know what we're working with).

Inside the box was a removable tray with many screws/bolts, and various other parts.
We see wheels and frame parts for the robot.
Above we see the antennae for the robot, some push-button sensors, and limit switches. 
No moving robot is complete without sensors...
Or a large book to keep track of it all.


After much time and effort, our first version of the robot is complete! We will come back to these later, after we learn another important tool to robotics: programming!

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