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

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Arduino’s broken Random()

If you are using your Arduino’s PRNG (Pseudo-Random Number Generator) for anything more serious than flashing random lights for your Christmas decorations, there’s a chance you might run into some unexpected issues, as the random() function in Arduino seems to be somewhat broken.

Why? Let me explain.


Most basic random number generators in programming libraries and platforms are based on what is called a “Linear Congruential Generator” (LCG), and I have discussed them before here in my blog. As with any PRNG, the output of the algorithm ends up being a sequence of numbers “seemingly” selected at random, starting from a “seed”.

Given the basic structure of an LCG, after you have drawn X numbers from the generator, you’ll start getting the same sequence again. This is called the “period” of the LCG, and is one of the things you should know about the PRNG you are using (again, if you are serious about your random numbers, or you need a controlled, predictable and stable behavior).

Arguably, you should always know the weakness and strengths of the PRNG you are going to use, before even using it, as to avoid any potential pitfall and/or limitation (and that’s why it’s normally not a good idea to use the default implementation of a random generator in any language; For the most of it you don’t know what you are getting).

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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

BT Audio Module with Aux Input

I have a very simple “audio/video” setup in my room. My main computer display doubles as my “TV” for playing videogames and watching movies. Technically speaking is just a 22″ HDTV with a bunch of input options, which I have connected to all of my devices, mostly through an HDMI hub, so I use the same screen for my computer, and my various consoles and audio/video devices.

Now, I’m not an audiophile, but as you normally get to expect, its integrated speakers are kinda too terrible to actually listen to anything through them for more than 10 seconds, so I have a couple of entry-level PC speakers connected to the TV audio output, which give relatively decent sound, or at least, better than with the monitor alone. Now, as all my gaming consoles and A/V devices go to the same TV, this is a pretty centralized setup, which is great for most of what I do, and has worked really well for years, but stops being great when I want to listen to something not physically connected to my system, like my phone, laptop, tablet, or whatever. So I thought of adding a bluetooth receiver somewhere in between.

After an online search I ended up buying this nice little module, which is essentially a BT 4.0 receiver that works with 5V. By default it will redirect whatever it receives through its physical “AUX IN” port to the output connector, but when a device connects to it over BT, it will ignore the physical input and play the audio it receives wirelessly instead.

The BT Audio module. As seen on most popular auction/e-commerce sites.

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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.

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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.

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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