A question came up on IRC regarding how to PWM a 3-pin PC fan with an Arduino using analogWrite(). Controlling the fan was seemingly straightforward. The problem was that the hall effect sensor, or TACH signal, was incredibly noisy. The noise made it impossible to measure the fan’s rotation. Working through the question, I found three issues to tackle:
You need to use a PNP transistor
Filter capacitors help
Create a non-blocking RPM measurement (with millis())
This post addresses all three issues regarding how to PWM a 3-pin PC fan with an Arduino.
Sharing is the maker community’s foundation. When you share projects with others, you contribute to the community. In the past, you might just post your project on a personal website. Today there are many options to share projects.
This weekend I “finished” my reflow oven controller, Open Vapors. Believe it or not, five years ago there were not a bajillion similar projects. In fact, I based my design on the only completely open source project I found. It is a reflow oven controller Arduino shield from Rocket Scream.
After completing my controller, I was excited to share the project. Then I started to think about where to post the files. Obviously, here at baldengineer.com is one option. But I wondered. Is there a better place where others could benefit from my work?
This post is a few notes on the platforms used to share projects. At first, these might seem like they all serve the same purpose. From a high level that is true. However, there are small differences that you should consider when you share projects with the open source hardware community.
When you buy a grab bag of components, you might need to tackle sorting resistors. Here’s how I sorted some bags of random resistor assortments last week.
Then method I use for sorting resistors achieves these objectives:
Fewer Bins. It doesn’t take long to create a large matrix of resistor values. My resistor sorting method is relatively compact.
Quick to find. When I’m building up a circuit, I don’t want to spend time sorting through a pile. Once I know the value I need, I find a single package and then look for a single color band.
Works with 4-band and 5-band resistors. Let me be upfront: I *hate* 5-band resistor color codes. While the 5th ring is supposed to be slightly offset, or wider, or a different type of color; it doesn’t matter. It’s nearly impossible to tell read a 5-band resistor color code when they are in a pile. However, using my method for sorting resistors, it doesn’t matter if I’m looking at a 4-band or 5-band resistor. I can immediately identify the resistor value.
Based on #3 alone, you might be wondering what is the fantastic method (and how much will it cost to get it!) Here’s the basics of my method for sorting resistors. (For FREE!)
Current flow (direction) is the topic I’m planning for my next AddOhms tutorial. While preparing the script, I started to realize there are some myths or misunderstandings about electricity and current flow.
Everyone probably knows Ben Franklin. He discovered electricity, of course! Yet, he didn’t. Franklin was the first to prove that lightning was composed of electricity with his famous kite experiment. He was also the first to provide electricity’s well-known labels: positive and negative. And somewhere in there Franklin became famous for “inventing” conventional current flow.
This convention creates a lot of confusion around conventional and electron current flow. It’s a concept that has been covered by many others and may even be covered by an Electronics Tutorial Video Series in the future.
Instead, I want to explore some common current flow myths even I believed at some point.
A switching voltage regulator is one of my favorite circuits. In school, they were the first circuits I built where I understood how transistors worked. In fact, they were the first circuit I saw an inductor being useful! Switching regulators are incredibly efficient when designed properly. Of course, this detail about design is important. They are not as simple as a linear regulator, which is basically an IC and two caps.
To understand the basics of a switching regulator, I released AddOhms #18 this week. This is video tutorial dedicated the Switching Voltage Regulator. If video tutorials aren’t your thing, then keep reading for my written tutorial.
Continue Reading »
The latest AddOhms looks at why you need a pull-up resistor when using push-buttons. This video goes into what happens when you leave a pin floating, what a floating pin means, and how the pull-up actually works. You can get more information about the video on the AddOhms Episode page.
This is the 2nd time I’ve made a video on pull-ups. Despite being a single resistor, it can be a difficult topic for new hardware designers to understand. The pull-up video was the first video tutorial I ever made. In fact, the YouTube version uses YouTube’s “stabilization” algorithm, which gives the video a very warped feel.
AddOhms #15 shows improvements in skill over the past couple of years!
Question: What’s another topic that I need to cover in an AddOhms Tutorial? You can leave a comment by clicking here.
The other day my friend called me up. He told me how much he missed building circuits and wanted to start again with the Arduino.
So he asked me “which Arduino starter kit is the best to buy?” At which point, I drew a long breath. Easy question, not always an easy answer.
Picking out an electronics kit depends on a number of factors. You should consider:
What you already have
What you want to do
#1 and #2 are probably pretty easy to figure out. For many beginners, it’s “not much” and “nothing.” When you don’t know #3, what you want to do, then it gets trickier. Coming back to my friend, what did I do? Well, I went out and bought each one of the kits in this post. I put myself in his shoes and maybe these are your shoes as well.
The funny thing about schematics is that they are much easier to draw than they are to read. There are many common circuits. When an experienced engineer looks at them, it’s like a second language. When someone less experienced looks at them, it looks like random lines and symbols thrown together at the last-minute. (Or maybe that’s just the schematics *I* draw.)
Other than reading Schematic Symbols themselves, one of the basic skill necessary to read a schematic is recognizing series and parallel circuits.
Learning to a breadboard is critical when adding electronics to a project. A skill often overlooked is how to use breadboard jumper wires correctly. For example, when I breadboard a circuit I only use Red, Green, or Blue for positive voltages and Black for ground. Other colors, it depends on the functions of the wire. The idea is to keep it clear when I look at the board, what each wire is doing.
This video from Make is a great overview of how to develop a skill, or habit, around using breadboard jumper wires in your circuit.
Engineers make a schematic to explain their circuits.
One time I was looking for a non-tourist pub in Japan. I asked someone for help. She said, “I’m sorry, but I do not speak good English. I will bring my friend and she will draw you a map.” (Exact quote!) The map her friend drew, gave directions to a bar with a “Neon Yellow Sing.” She meant sign…
The map was the method we used to communicate with each other, even though we didn’t both speak English. With this crude but effective map, I could find my next drinking place destination.
Schematics are the same as this map. Even if you don’t speak the same language, you can communicate how a circuit works when you make a schematic.