In case you haven’t noticed, the Hackaday community is making more of an effort to be a community AFK. We’re at VCF East this weekend, have the Hackaday World Create Day quickly approaching, Hackaday | Belgrade a few days ago, and Hackaday Toronto next week just to name a few in close proximity to this post.
As promised, or threatened, depending on which end of the stick you’re on I will be teaching an electronics class at the Dallas Makerspace every 3rd Saturday of the month. The goal of these classes is to help you overcome the barrier between a hardware idea and having that hardware in your hand. I’m not an expert in PCB design or layout, but I’ve found more ways to do it wrong than I’d probably admit too and this is my way of sharing what I’ve painfully learned through trial and error. At the time of writing this article there are still a few spots available in the first class, follow the above link for tickets.
Images of my failed hopes and dreams wonderfully captured courtesy of [Krissy Heishman]
In our first 6 hour session we’ll take a basic, high-level idea and work our way down. For example: our first project will be an AVR development board. This is something common enough that everyone will know what it is (an Arduino is an AVR development board, just in case my mom is reading this). We won’t be making an Arduino clone part-for-part but taking the Arduino idea and making it our own custom board. Maybe we add some terminal blocks instead of DuPont headers or perhaps we want a real time clock and a slide potentiometer on the board. We can do that if we want, you can’t stop us.
So class number 1 is a crash course in Eagle schematic capture and PCB layout. Since this is only 6 hours worth of class time and we need to have boards and parts ordered when we leave we won’t be getting too complicated with our design.
By the time we meet for our second session we should have taken delivery of our shiny new PCBs and our parts order should have long since been delivered from the distributor (Mouser is more or less an hour drive from the Dallas Makerspace, not that we’ll pick the parts up at will-call for this project, but it’s nice to have the option). We will spend the second 6 hour session assembling and testing our boards. If we need to make changes to our boards we can talk about that as a part of the design process. Depending on how long assembly takes we can brainstorm some ideas for the next round of Mrs. Penny’s Driving School classes which will continue the following 3rd Saturday of the month.
Many successful large-scale projects don’t start out large: they start with a small working core and grow out from there. Building a completely open-source personal computer is not a weekend project. This is as much a retelling of events as it is background information leading up to a request for help. You’ll discover that quite a lot of hard work has already been put forth towards the creation of a completely open personal computer.
When I noticed the Kestrel Computer Project had been submitted via the Hackaday tips line I quickly tracked down and contacted [Samuel] and asked a swarm of questions with the excitement of a giddy schoolgirl. Throughout our email conversation I discovered that [Samuel] had largely kept the project under the radar because he enjoyed working on it in his down time as a hobby. Now that the project is approaching the need for hardware design, I posed a question to [Samuel]: “Do you want me to write a short article summarizing years of your work on Kestrel Project?” But before he could reply to that question I followed it up with another: “Better yet [Samuel], how about we tell a more thorough history of the Kestrel Project and ask the Hackaday community for some help bringing the project home!?” Continue reading “Kestrel Computer Project”→
In the first article about measurement systems we looked at sensors as a way to bring data into a measurement system. I explained that a sensor measures physical quantities which are turned into a voltage with a variable conversion element such as a resistor bridge. There will always be noise in any system, and an operational amplifier (op-amp) can be used to remove some of that noise. The example we considered used an op-amp in a differential configuration that removes any disturbance signal that is common to both inputs of the op-amp.
But that single application of an op-amp is just skimming the surface of the process of bringing a real-world measurement of a physical quantity into a digital system. Often, you’ll need to do more work on the signal before it’s ready for sampling with a digital-to-analog converter. Signal conditioning with amplifiers is a deep and rich topic, so let me make it clear that that this article will not cover every aspect of designing and implementing a measurement system. Instead, I’m aiming to get you started without getting too technical and math-y. Let’s just relax and ponder amplifiers without getting lost in detail. Doesn’t that sound nice?
The Hackaday Prize meetup at the Dallas Makerspace is this weekend: Saturday March 19th. We will be kicking things off at 7pm with food and drinks followed by lightning talks. If you want to come but have yet to RSVP you can do that via Meetup, please do this so we can have enough food and drinks on site for everyone.
We’ve already lined up a number of lightning talks (5-7 minutes each) to get things started so we aren’t sitting and staring at one another like a junior high dance. But we encourage you to show up and sign up for one on on the night of the meetup. Even if you don’t give a talk you should bring a project to show off afterward.
Lightning Talks Primed With:
[Brandon Dunson] giving a talk about the 2016 Hackaday Prize, [Mike Szczys] will be giving a talk about the Hackaday | Belgrade hardware badge. [Dave Anders] will be talking about his WITCH-E Project and [Bradley Mahurin] is bringing his 450V 1mA PIC based boost converter. Not to discredit the Hackaday talks, but I’ve seen [Dave] and [Bradley]’s work before and you’ll want to see this stuff first hand and get a chance to talk with these guys.
Most hobbyists use crystals as an external clock signal for a microcontroller. A less common use would be to make a bandpass filter (BPF) for an RF signal. [Dan Watson] explains his crystal ladder design on his blog and links to several sources for understanding the theory and creating your own crystal ladder band pass filter. If you want a set of these purple PCBs you can order them straight from the purple fab.
One of the sources that [Dan] cites is [Larry Benko]’s personal site which is primarily dedicated to amateur radio projects. Which you can find much more in-depth information regarding the design of a xtal BPF. [Larry] goes into detail about the software he uses and some of the applications of crystal ladder filters.
The process includes measuring individual xtals to determine which ones will work together for your target frequency. [Larry] also walks you through the software simulation process using LTSpice. If you aren’t familiar with Spice simulation you can get caught up by checking out the series of Spice articles by our very own [Al Williams].
The physical world is analog and if we want to interface with it using a digital device there are conversions that need to be made. To do this we use an Analog to Digital Converter (ADC) for translating real world analog quantities into digital values. But we can’t just dump any analog signal into the input of an ADC, we need this analog signal to be a measurable voltage that’s clean and conditioned. Meaning we’ve removed all the noise and converted the measured value into a usable voltage.
Things That Just Work.
This is not new information, least of all to Hackaday readers. The important bit is that we rely on these systems daily and they need to work as advertised. A simple example are the headlights in my car that I turned on the first night I got in it 5 years ago and haven’t turned off since. This is not a daytime running lights system, the controller turns the lights on when it’s dark and leaves them off during the day. This application falls into the category of things that go largely unnoticed because simply put: They. Work. Every. Time. It’s not a jaw dropping example but it’s a well implemented use of an analog to digital conversion that’s practical and reliable.
The RF signal transmitted from a modern key fob and received by the associated vehicle is only used once. If the vehicle sees the same code again it rejects the command, however there is a loophole in those carefully chosen words. The code must be received by the vehicle’s computer before it can be added to the list of spent codes. [AndrewMohawk] goes through the process of intercepting a code sent from a key fob transmitter and preventing the vehicle from receiving it in a thorough post to his blog. You can see this attack working in his studio quality reenactment video after the break.
[Andrew] uses the YARD Stick One (YS1) which is a sub-GHz wireless tool that is controlled from a computer. The YS1 uses RfCat firmware, which is an interactive python shell that acts as the controller for the wireless transceiver.
This system is not without its problems: different frequencies are often used for different commands, [Andrew]’s scripts are designed to work with On-Off keying (OOK) leaving it useless when attacking a system that uses Frequency-Shift Keying (FSK). There is also the issue of rendering a target key fob non-functional but you’ll have to pop over to [Andrew]’s blog to read more about that.