This week, after going through the videos, try building some circuits in parallel and in series on your own. Use multiple switches and LEDs. Measure things with your multimeter. Can you make a schematic and turn it into a circuit or look at a simple circuit and make a schematic from it?
Here’s your challenge for the week : build a circuit that turns on some LEDs by closing a switch which you do not use your fingers to operate directly. Examples to get you thinking : a switch that turns a light off when you aren’t sitting up straight, a switch that is activates when you put your keys on a hook at home, a switch that you use your nose to operate, a switch that turns on when you’re having a drink or eating food.
As you complete these, post them in Slack under the #no-hands-switches channel.
These notes complement and somewhat follow the outline of the videos created for the workshop. Each underlined heading links to a tutorial page with more information on the topic.
- Electricity Basics
- Electricity is the flow of negatively charged electrons through a given material (usually copper wire or another conductor). We use this natural phenomenon to power a variety of devices and circuits.
- Electricity can be harnessed and converted, used to create light or motion, to transfer data and communicate between systems.
- AC / DC
- AC – Alternating Current
- Current oscillates.
- fantastic for long distances/ high voltage / current applications
- Supplied from the electricity grid through wall outlets.
- In the US, AC is rated at 110/120 volts, and 60 Hertz
- In the UK, EU and other countries, it’s rated at 220/240 volts at 50Hz
- A list of all variations can be found here : https://www.school-for-champions.com/science/ac_world_volt_freq_list.htm
- DC – Direct Current
- Current flows in one direction.
- Typically the end of the line
- Most commonly found in day-to-day objects: battery powered tools, handheld and consumer electronics.
- Some devices — incandescent light bulbs, certain motors, heating elements — operate directly from AC current. Others (like many consumer electronics) accept AC current but translate it internally into DC current. Still others can only accept DC current.
- AC – Alternating Current
- Ohms Law
- V=IR — The foundational equation for how to calculate the different properties of a circuit: voltage, current, and resistance.
- Voltage is the difference in charge between two points.
- Current is the rate at which charge is flowing.
- Resistance is a material’s capacity to resist the flow of charge (current).
- Ohms Law becomes relevant when building a circuit, but also when troubleshooting a circuit. For example: identifying whether the voltage being supplied to a circuit is being used in its entirety and/or if any excess is being absorbed by the appropriate resistors.
- V=IR — The foundational equation for how to calculate the different properties of a circuit: voltage, current, and resistance.
- What is a circuit?
- Circuits are closed loops that allow electricity to flow from a point of higher potential energy, such as a the positive lead on a battery, to a lower potential, through a load like a lightbulb.
- They control the movement of electricity in service of a specific purpose or outcome through assemblies of electrical components.
- The key components of safe and effective circuitry include:
- Understanding how to make sure that power flows correctly (and in its entirety) from an electrical source/power supply to a chosen output like a lightbulb or sound device.
- The necessity that circuits be complete (closed) in order to function.
- Understanding what causes short circuits and how to avoid them.
- Three things to remember about circuits
- All voltage is used in a circuit
- Electricity will follow the path of least resistance
- The amount of current flowing into a spot in a circuit is the same that flows out
- Power vs Signal
- Electricity can be used to power a device or to create a signal. Examples of a power: to run a motor, turn on a lightbulb, etc.)
- a signal is a method of communication between devices, for example between 2 integrated circuits
- Circuits created for these different purposes share many things in common, but also have unique requirements. When creating a signal, elements like frequency and noise become important. Different materials may be used to construct (and different tools may be used to test) a power circuit as opposed to a signal circuit.
- Electricity can be used to power a device or to create a signal. Examples of a power: to run a motor, turn on a lightbulb, etc.)
- Power Supplies
- The source of electricity for your device/installation
- Could be batteries, wall worts, solar, wind, electro-magnetic in origin
- These will provide power for the work your circuit will do. Typically plugged into a wall, but we’ll be using 9V batteries for most of this workshop
- power for work could be either AC or DC
- Power supplies come in great variety and it is essential to identify the appropriate supply for a specific device.
- Key Components of a power supply:
- Voltage and Current
- AC/DC
- Polarity
- Polarity
- Polarity indicates whether a circuit component is symmetric or not. A non-polarized (symmetric) component can be connected in any direction and still function the way it’s supposed to function. A polarizedcomponent can only be connected to a circuit in one direction. If connected in the wrong orientation, at best it won’t work as intended. At worst, it will smoke/spark/die.
- A common AA battery is a simple example of a polarized component: with positive and negative terminals that must be correctly aligned for it to function. Polarized elements in a circuit can be much more complicated though, with multiple connection points that each have a unique function and position.
- How to Use a Multimeter
- A multimeter is multifunctional tool that can measure voltage, amperage, resistance, and continuity across a given component.
- Breadboarding
- Breadboards offer the opportunity to prototype a circuit before constructing it in a more permanent form.
- How to read a datasheet
- Datasheets give us information about how our components work. Every item you received will have a data sheet associated with it. Here’s a Google Drive folder with data sheets of the materials you purchased.
- Regulators
- a type of component that drops voltage across its pins. the excess is released as heat. We’re using a 7805 regulator, which drops the voltage in a circuit to 5V
- resistors
- resist the flow of electrical energy. Used to limit current and drop voltage.
- measured in ohms, you can determine the amount of resistance with a multimeter, or using a resistor color calculator
- never polarized
- capacitors
- components that store and discharge electricity over time. They are often used to smooth out irregularities in current and voltage.
- measured in farads, the amount of capacitance can vary and come in a wide variety of shapes and sizes
- some are polarized, others are not
- LEDs
- a kind of diode, and the most fun. they are polarized components that emit light when voltage is applied
- switches
- used to control the flow of electricity in a circuit. There are many shapes, sizes and kinds. The small pushbutton ones we have are momentary, but there are also latched ones that work like a lightswitch in that they hold their position.
- used to control the flow of electricity in a circuit. There are many shapes, sizes and kinds. The small pushbutton ones we have are momentary, but there are also latched ones that work like a lightswitch in that they hold their position.
- Series vs. Parallel circuits – build circuits below on a breadboard and measure with ‘scope and meter & make unique switches
- If components in a circuit are in series, there is only one path for current to flow through them.
- In parallel circuitry, current can take multiple paths between elements/components.
- Schematics
- A Schematic is a map of how to properly connect a given circuit. Symbols represent various components (like resistors, capacitors, switches, ics, and power sources) and lines represent connections between those components.