I recently signed up to teach a series of classes at Denhac, the hackerspace in Denver. It is part of a new movement to get members to teach their specialty, and there is a lot to learn for folks in the area. Totally free and open to the public! For those that can come, it's on 4/16/12 with lecture #1 at 1:00pm and #2 at 2:30pm, located at 975 E 58th Ave, Unit N Denver, CO 80216.
I spend nearly all of my design time working on analog electronics, and the majority of the Denhac community is digital/software engineers. So I made a lecture series for anyone with a casual interest in electronics to get their feet wet. I'm targeting FPGA/Microcontroller/Software engineers that want to know about the hardware that accompanies their digital systems, or anyone that would like to get into electronics tinkering. My goal is to help my fellow engineers and enthusiasts walk away with:
- The vocabulary to understand the issues that analog engineers face, and what it might mean.
- The ability for a digital designer to look awesome in front of a boss or design team. I am very impressed when a digital person says something like, “Hey Dave, I had to change the voltage on the microcontroller from 3V to 5V. Could you use that extra signal range in your op amp circuit that feeds the ADC?”
- An understanding of difficult constraints that analog engineers are bound to that may not be obvious. This might prevent asking something like why it is such a big deal to add 50% more current to a power supply rail.
- For novices to be able to design their own simple analog systems. If someone wants to build a weekend project, he or she should not feel hesitant because of a power supply or op amp problem.
Each talk is intended to be ~1 hour long with a relaxed, fun approach. I imagine it will be a bunch of people hanging out on a Saturday afternoon learning stuff, building stuff, and drinking beer. Since I'm making this stuff up as I go along, I'm posting my plans for the first two lectures here to see if anyone has suggestions to make it better!
Lecture 1: The Basics. A Personified Approach to Voltage, Current, Resistance, Power, Resistors and Capacitors.
The Starting Point: Electrons are everywhere! We just have to motivate them to do what we want.
Voltage: Our way of motivating electrons. A 1.5V AA battery gets only motivates electrons a little bit. A 120V wall outlet motivates them much, much more.
DC Voltage: 'Direct Current' which means it applies a consistent voltage level. Things like batteries, USB ports, car outlets are like this.
AC Voltage: 'Alternating Current' which means it applies a voltage that is constantly changing, like a Sine wave. A wall outlet is 120VAC, and is a sine wave reaching +170V at the top peak, and -170V at the bottom peak (which comes out to 120V RMS).
Current: How many electrons move through a wire.
Resistance: How hard it is for the electrons to move.
Ohm's Law V = I*R: How Voltage, Current, and Resistance are related. The more resistance in a current path that exists, the more voltage is required to motivate the electrons to move.
Example: Battery with a resistor on the whiteboard.
Power: Consumed by anything with electricity going through it and can be simplified to Voltage * Current. (P = I*V).
Example: Calculate power consumed by a microcontroller using 200mA from the 3V rail and 150mA from the 5V rail on the whiteboard.
Resistors: Really just a carefully designed wire that, based on the material, length, and diameter, have a specific resistance value.
Capacitors: Two metal plates positioned very close to each other, but not touching. The amount of capacitance can change by (1) the size of the plates, (2) How close they are to each other, and (3) the stuff that is between the plates (air, plastic, goop, etc...).
Capacitors in a DC situation: Like a reservoir for electrons. Great for smoothing out supplies.
Capacitors in an AC situation: They act kind of like a variable resistor. At low frequencies, they have a very high resistance. At high frequencies, they have a very low resistance.
Example: Cutting out 60Hz noise from lights with a passive RC filter on the whiteboard.
Lecture 2: Silicon Basics: Diodes, BJTs and FETs, and Op Amps
Diode: Ideally it is a 1-way street for electrons. Show the I-V curve and chat about zener diodes.
Transistor: A switch that we can control by either putting in a little current or applying a little voltage to the control pin.
NPN BJT: Show a schematic diagram and describe Base, Collector, and Emitter. Show how to turn the current from collector to emitter on and off by applying a current to the base.
Example: Controlling a high power 1W LED from an arduino with a BJT.
PNP BJT: Show a diagram and how to control it.
N-Channel FET: Show a schematic diagram, describe gate, source, and drain. Show how to turn the current from drain to source on and off by applying a voltage to the gate.
Example: Controlling a high power 1W LED from an arduino with a FET.
P-Channel FET: Show a diagram and how to control it.
Operational Amplifiers: A collection of transistors all in one part. They can make a better op amp for $0.25 than you can by crafting one with your own transistors for months!
Op Amps: Show a schematic diagram and what all the pins are. Then discuss the rules (1) the output will do what it can to make the + and – pins at the same voltage. (2) The + and – pins are like volt-meters, and no current will go in them.
Op Amps: Show all of the cool stuff you can do with them. Buffer, amplify, filter, differentiate, integrate.
Op Amps: Why they usually don't work on the first design try and what to check.
So what do you think? Analog people: would you add or subtract anything from this plan? How about anything you digital people might like to see that is missing?
Wish me luck!
