Here are the slides from the class: BasicElectronics_1_20130320 . Note: We are preparing a follow up class that dives further into the subject. Please keep an eye out for the announcement.
There is limited seating available so Please register if you wish to attend. Wed, March 20th.
Part 1. Ohm’s law and Watt’s law
This class will teach the basics of voltage, current, and power. A lab will be included that will demonstrate how to calculate the proper value of resistor to connect LEDs to power.
Parts and equipment may be borrowed from the hackerspace or you can purchase a multimeter (http://www.harborfreight.com/7-function-digital-multimeter-92020.html), a few LEDs, a few resistors, clip leads, and a 9V battery for $5. Alternatively, you can bring your own.
Chris Cockrum of the Baltimore Hackerspace will be giving a course on Cryptography this Wednesday, February 20th at the Baltimore Hackerspace. He will be teaching the fundamentals of public and secret key cryptography including exercises on RSA, elliptic curve, and cryptanalysis using Sagemath (Python Based).
During last night’s Open Hack Night, while trying to explain things like how transistors and mosfets work, it was discussed that maybe taking a step back and outlining some of the basics of electronics would be beneficial to everyone. So I decided to start with Ohms Law.
Voltage is measured in… well Volts of course!
Current is measured in Amperes.
Resistance is measured in Ohms! Named after this guy who put a bunch of work in discovering resistive properties electricity, and apparently came up with this relationship known as Ohms Law. Anyhoo.
I like analogy’s to help me relate things that I know, against things I don’t know. So everyone’s favorite analogy of electricity is water. Some will argue this topic to death, but for my purpose I’m sticking to it.
Voltage — So Voltage is actually a potential concept, think of a large water tank on the top of a hill and a small pipe coming out of the bottom. The difference between what is coming out of the pipe versus the pressure in the tank is the potential voltage. So voltage is the pressure.
Current — This would be the volume of water pushed through that pipe by the voltage (pressure) and would refer to the quantity of water flowing through it.
Resistance — So this would be the pipe its self. The larger the pipe (lower resistance), the easier current can flow through, thus having more current. The smaller the pipe (higher resistance), the harder it is for the current to flow through the pipe, yielding less water.
So we’re still busy decking out the new facility and one of the things we wanted to get up and running is some cheap surplus ethernet cameras to … keep an eye on things and check out whats going on remotely. So I thought I’d go ahead and set these guys up.
First thing up was to make some cat5 cables. I got a cheapo crimper, cable tester, and connectors off eBay. While trying to figure out how much cable I need to run I was thinking about how I’m going to plug the cameras in to supply power. They have wall warts with barrel jacks running 12 volts. I started thinking about how power over ethernet works and thought I’d try to see how I can do the same thing to run the power to the camera. These aren’t POE cameras so the idea was to only half crimp the connectors, and use the unused pairs to run the 12 volts.
Here is the layout of how cat 5 cables should be done. Credits to wikipedia.
So there are 2 color coded standards for crimping cables, but oddly enough, the ones we care about are blue, blue/white, white/brown, and brown. Pins 4, 5, 7, 8. These pins aren’t used in 10/100 connections, however if it was gigabit then they would be used. So the unused pins are the same on both standards, so I just chose the first one.