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.
The copper layer thickness in a printed circuit board (PCB) is rated in ounces (also called the copper weight) or in mils (also called the copper thickness.) Both units of measurement are relaying the same information just in a slightly different format. For example, 1 oz. of copper is equivalent to 1 square foot of 1.4 mils (.0014″) thick copper.
Copper weight/thickness is important in several areas of PCB design. The thickness and width of a trace determines the amount of current (amps) the trace can carry. The thickness is also used in the calculation of trace impedance (ohms) in RF and high speed digital circuits.
The following is the formula for cpw (in oz) to thickness (in mils) conversion:
Thickness(in oz) = thickness (in mils) /1.37
The following is the formula for thickness (in mils) to cpw (in oz) conversion:
t ( in mils) = t ( in oz) * 1.37
|1/2 Oz.||.7 mils|
|1 Oz.||1.4 mils|
|2 Oz.||2.8 mils|
Copper Weight / Thickness Chart
After a recent hard drive failure, I realized I need to start doing some proper backups (Duh, right?) Anyway, while shopping for hard drives to build a backup NAS (for which I need some internal drives, not external USB drives) I discovered a trend where a lot of external hard drives are cheaper than internal drives at the same capacity. How does this make sense?
I ended up purchasing these 3TB hard drives for about $140 each at Office Depot. It’s a crap shoot on which hard drive will be inside, but it will normally be made by the same manufacturer, and be of that capacity. (You would be surprised to find out this isn’t _always_ the case).
Being a 3TB Seagate, a quick search over at Newegg shows this drive which sells for $229. That’s a $90 dollar difference. WOW! So doing this instead of buying internal drives is a bargain so far.
Just playing around with the iPad app Animoog, which I believe is still available for $0.99 at the iTunes app store. This is a huge bargain on a really really cool app. I won’t get into the specifics of the app, but if you want to know more about what Animoog is or how to use it, I recommend this YouTube video.
So, while playing around with the Animoog app, if you go into the setup menu there is a selection under ‘Refresh MIDI input(s)’ where you can select ‘Off’ or ‘Network Session 1′. This intrigued me! Apparently you can use MIDI over the ‘Network’. After some Googling I was still unclear on how to get this setup, so I thought I’d just tell everyone how I did it so you can get to making some cool tunes yourself.
Over the last few weeks Harford Hackerspace has had the pleasure of beta testing the Netduino. The Netduino is a development board with a form factor similar to the Arduino. Care was taken when designing the Netduino to ensure compatibility with most of the existing Arduino shields. That’s about where the similarities of the two devices ends.
The Netduino uses Microsoft’s Open Source .net Micro Framework SDK along with Visual Studio C# (or VS C# Express) as the primary development environment. C# application developers will be able to quickly adapt to the .net Micro Framework and start programming microcontrollers in a matter of minutes. However, this does not let them off the hook for learning the basics of electronics.
Around the space, we have been using the PICkit 2 Debug Express quite a bit lately. This has allowed us to get pretty cozy with the functions of this handy little programmer and I thought I would share some of these features with you.
I’m sure you’ve read the previous tutorial ‘Programming PIC Microcontrollers in C‘, if you haven’t, you should go familiarize yourself with it now. Continuing on from there, after we have a successful build of a led blinking we can use the PICkit 2 to program our chip via the ICSP header.