JuanGg Projects

  This is the final lab from the analog half of Learning The Art of Electronics . I've had the thing assembled in some solderless breadboards for over a year and decided to make some PCBs for it. Here are some pictures of the assembled PCBs: PCB milling (FlatCAM): 0.2 mm 30º V bit, 20000 rpm, 300 mm/min, 50 um depth, autoleveling. Isolation (2 pass) + Copper clear on selected regions (missed some). 0.8 mm & 1 mm holes. And the unpopulated boards out of the CNC machine: The breadboard prototype can be seen on the "About" page of this blog.

Here is a university project I particularly enjoyed working on and I hope some ideas here are useful some somebody else.   The task: Computer Vision project with something to do with Face Detection.   The project: Simplified Viola-Jones implementation (in MATLAB), from the ground up. Following is an overview. I won’t publish any code; you’d miss out on all the fun! First, reading and sources: Of course, the original paper : Robust Real-Time Face Detection. Viola P.; Jones M.J. (2001) And the material from CSE 455: Computer Vision Shapiro L. (U. Washington) (2017): Image datasets, more down to earth theory and implementation suggestions. Quick overview: Some “features” made up of rectangles are generated randomly within some bounds. One can compute the value of each feature for a particular image by adding pixel values under white rectangles and subtracting those under black rectangles. What’s called an Integral Image speeds ups computations significantly. The name of t

I'll be adding here some tips and how-tos on how on FlatCAM 8.994, an Open-Source PCB CAM tool. This is a work in progress and it's mostly for my own reference. I'll be updating it as I discover new stuff. Note that procedures shown may not be correct or the most efficient. This is provided "as is". FlatCAM's website:  http://flatcam.org/ Installation:  https://bitbucket.org/jpcgt/flatcam/downloads/ Create and save new project: Load Gerbers & Excellon: Single-sided isolation routing: On the left pane, double-click your front copper gerber, and you'll be taken to a Properties window. Choose Isolation routing. If the left pane somehow disappears, you may go to View > Toggle project/Properties/Tool. On tools & tools library: From within the isolation window, delete default tools and choose the tool you want to use, or create a new one. See the screenshow on how to do so. Here is how to configure a traditional V bit. To be continued... Soon (TM) Don

  Sometimes a water alarm may come in handy around the house, to notify you of leaks so you can do something about it before the mess grows beyond control. I designed and manufactured a rudimentary alarm that senses water through a simple conductive probe, and compains about it. It made for a perfect excuse to get back up to speed with KiCad and LTSpice, to recover from MicroSIM (1996 edition, ever heard of it? me neither) which they make us use at school. Beeing able to pan and zoom using the mouse is definitely something I've missed. Here is the schematic: A couple of transistors form an SCR-like circuit that latches on if water is detected. This powers a two transistor oscillator than in turn drives the buzzer. Almost zero power consumption on standby. Most values are non-critical, and timings are difficult to predict in this kind of circuits, as transistors have to be driven with certain base current to turn the buzzer on and this interferes with the time constants of the RC se

I had been wanting to build a CNC router/mill for a while, so finally on January 2021 I designed this contraption, with the help of the folks at cnczone . I originally wanted to go for an aluminum or even concrete frame, but as a first project and for ease of construction and economic reasons it ended up being wood. It is intended for cutting woods and plastics, and PCB milling. I'll try some alumi(ni)um when I'm familiar enough with feeds and speeds. I then proceeded to cut out all wooden pieces, finishing the edges with a hand-held router so that they were reasonably straight. When summer came and all parts (rails, leadscrews, steppers..) arrived, I began gluing all the pieces together and test-fiting parts. Areas where linear rails mounted were soaked in epoxy to protect the wood. Holes were drilled and tapped for the appropiate sizes, regular machine screws would latter hold things together, with some drops of wood glue to secure them semi-permanently in place. A workbench

  This is a lab power supply I put together back in 2018 with one DPS3005 module. It is easily the most used piece of equipment in the lab, so much that it is permanently on. The module itself is nothing but a DC-DC converter capable of 30 V and 5 A, providing a simple user interface, and isolated USB control (which I've never really needed). The output is pretty noisy as one might expect, see discussion  here . An LC filter reduced some of that noise significantly. I'll have to come back to it and re-do it with smd capacitors, yet I have no real need. My other lab supply  has way lower noise. I first used a cheap swithcing supply to power the module, but it lasted a mere week or so. I later substituted it for an unregulated dc supply using a transformer I bought at the local flea market. The case I made for it being wood, I added a small fan in the back. I quickly added a simple two-transistor temperature controller because of the noise. With all fans running (power supplies,