Making a dedicated Logic Analyzer, Part 2

It took me a really long time to do this second part of my Pi-based Logic Analyzer project, mostly because of two things; the first one being that at one point (after I had pretty much all the case design, extra hardware and software tweaking done for my RPi1) I decided to switch to a Raspberry Pi 3, which of course meant discarding a lot of work and starting again but with the RPi3 in mind.

Why? Because I figured that my device was getting needlessly bulky (the case required extra room for a small fan (for the overclocking), extra width for the full-size SD card, and extra thickness due to the back-facing P5 connector, etc), and it would have been almost impossible for others to replicate this project (because I was using the old Pi1 Rev.B board, which is discontinued) so using a more modern Pi made sense. The physical layout of the Pi has stayed the same since the latest revision of Pi1 I believe, and -sans the position of the status LED- both the Pi2 and Pi3 are identical and completely interchangeable for the purposes of this project.

The second reason for the delay was that in an spectacular display of stupidity, I managed to fry my Waveshare TFT screen when I was done with the whole setup and designs for the Pi3, so I had to order another one online, and wait until it arrived, which took a long time. Read More

0-30V 3A Linear Power Supply Kit

It has become pretty common for me to have one or two unfinished projects on my bench or the shelf, because “I just can’t find the time” to complete them, or because I’m “waiting for something the project needs”. And both things happened in one way or another with a Linear Power Supply kit that I bought after watching a review/build by VoltLog.

I ordered the kit online, and before it arrived I went and purchased a 24V 3A transformer from a local electronics store, eager to build and test the kit as soon as I got my hands on it. By the end of July I received and soldered the kit. The enclosure arrived later I think.

Looks fun, right?

The beginning of the delays

Read More

Enclosure for a D3806 Buck-Boost Switching Power Supply

I kinda like the end result.

Not long ago I purchased this neat and compact DC to DC Buck Boost converter that performs reasonably well. It has a maximum output of 38V, 6A and has more than enough flexibility and features to be a secondary power supply in my lab.  I recently found a review of this product by Julian Ilett on his channel (which I’ve been following for a while) and the way it works is quite clever. The problem for me, however, is that it was a bit messy to have the bare circuit board laying around unprotected on my bench. The top-mounted panel wasn’t too practical either, and it was becoming increasingly clear that it was meant as an adjustable power converter module rather than a supply. Read More

UV Exposure Box Project – Part 2

I disabled the safety feature just for this shot. You are welcome.

This is the second part of my adventure building a UV Exposure box, in which as you can see, I actually finished the build. In the first part I made the structure and planned the electronics. This part covers a whole lot more, distributed over many weeks doing small things here and there. Read More

An update to my desk clock

I like to call this revision “Please believe me, I’m not a bomb”

Like a year ago I made myself a nice little desk clock that has worked fine since then. But recently I revisited the project to do certain improvements.

For starters I wanted a smaller board so I could fit it inside an enclosure.  I also wanted to power the clock from a rechargeable 18650 battery and add the charging circuitry to the design. I was also willing to give up with the ultra low power consumption and use a DC-DC booster that would of course draw more current but would ensure the clock gets a nice and stable 5V at all times. This has two advantages: It keeps a constant brightness for the display, and, more importantly, will give me reliable 5V in the aux port so I can easily interface the clock with other devices or external circuitry if I so desire. Read More

Power supply for a DIY function generator kit

I love DIY/soldering kits, and thanks to online marketplaces like eBay I’ve been able to purchase and assemble a number of them for the past few months.

One of the last ones I got was a very basic but useful function/signal generator, whose only problem was that it required a power supply with +12V/+5V/-12V rails (it also arrived already assembled despite being sold as a DIY kit, which was disappointing in a way).

My firsts tests of the kit were with a PC power supply (the only source of -12V I had in my lab) until I got a “proper” alternative in the form of another kit, which is sometimes advertised as a “Hiland USB Dual Power Multiple Output Supply”. I will call it HL supply during this post (Mine says “Hyland” on the PCB, so assuming an original version exists mine is probably a cheap clone). This one actually required assembly (yay!) and worked fine in my limited tests, but it was still a hassle to have the two boards dangling around connected whenever I wanted to use the signal generator, so after some time I decided to make a (temporary) enclosure for the whole thing.

Read More

UV Exposure Box Project – Part 1

In my neverending quest of improving my homemade PCBs, I discovered that adding a soldermask to my boards is actually not a hard task, thanks to a relatively simple process that involves UV-curable paint. Now, while using the sunlight as a UV source should work just fine, I decided that it was time to build a proper UV exposure box. Winter is quickly approaching and I’m not too fond of the idea of having a variable-intensity light source (the sun) that would make the process (and end result) completely dependent on how good was my estimation of the time required to properly cure the paint given the weather of that particular day.

A UV Box would also allow me to experiment with UV-based transfer methods for the PCB etching process as well, so it was definitely time to build one.

UV Exposure Box. Closed.

Read More

Using your Pocket C.H.I.P as a portable Logic Analyzer

Pocket C.H.I.P + USB Analyzer

So a time ago I purchased a cheap USB Logic Analyzer from eBay that works great with a PC, and it’s been really helpful to debug several projects to date. It uses the Logic software from Saleae as hinted by the label on it, although I am not sure if the device is supposed to be a cheap knockoff of one of the (pricier) genuine Saleae analyzers, or it was just designed to be “Saleae-compatible” and use their software. Read More

Mini HTTP Daemon Service for RaspberryPi/Linux apps

So recently I had to design a relatively convoluted system with a database that communicates with a hardware controller board and a RFID reader. Among other things, the system has to respond to several commands issued from a web frontend over HTTP, and report the status of each sub-system, sensor, etc hopefully in JSON or similar web-friendly format.

For this task I picked a Raspberry Pi as the platform, and made a program in C that talks directly to the hardware and handles everything including the HTTP requests.  Now, this is definitely not the first time that I need to write a program that has to listen for requests and reply with simple data over HTTP,  so I thought that perhaps it would be useful to encapsulate this functionality in a small module that I could later re-use in other projects.

So I ended up doing exactly that, and uploaded the code to my GIT-Hub Repository, so you’ll find the result from that here: https://github.com/battlecoder/httpdpi.

Before you dive into the code, please bear in mind that it’s an extremely simple service that will only respond to GET requests, but has all it needs to reply with different status codes, text, and binary data. It only uses sockets and POSIX threads, so it’s very fast, doesn’t depend on a huge framework, and can run in parallel with your code. It’s also really easy to expand if you want to support other types of requests.

Since it doesn’t have obscure dependencies, it should also compile on most linux boxes including other small computers like C.H.I.P, Beaglebone, etc.

Read More

DIY Table Saw for PCBs and thin wood

Cutting PCBs down to size for each project has always been a problem for me. I don’t have a bench saw, so I’ve been doing this by hand until now. Despite the number of boards I’ve made, I still lack the dexterity to do perfectly straight cuts with a regular hacksaw, and my success with other manual methods has been equally limited.  Like a year ago I stumbled upon a small a table saw on dealXtreme which I was tempted to buy but was kinda too expensive for me. My search continued until a few months ago, when I realized that I could make one myself, using a small motor I salvaged from a cheap $10 dremel-like tool that I once had. I wasn’t sure this was going to work, but decided to give it a go nonetheless.

At least looks like a table saw. That’s always a good sign.

Read More