Juan's Projects

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 supp...

So, this is the project I've been working on for the past 10 months, a 6502 compatible (but for timing and decimal mode) TTL CPU and accompanying computer. I'm slowly working my way through Learning the Art of Electronics, and the digital part of the course requires quite a lot of specialized material. To make up for the practical sessions, I decided to build a CPU from 74XX ICs. The original idea was to make something like this project  , but then I found out about the 6502 and things went a bit out of hand. I started designing the CPU in Logisim, using Python to write microcode and the ALU ROMs contents. After several versions and a lot of debugging, it finally executed Klauss Dorman's 6502 test suite, taking an entire week to do so in the slow Logisim simulation. Most schematics were laid out and the entire CPU was built in little more than two weeks, on "holidays" between university semesters.  Quite some productive time I must say. Lots of debugging and modif...

I've got the schematic from here . It doesn't work just yet. I'm working on it.

Just a simple BFO (beat frequency oscilator) metal detector based on  this one . It is comprised by two LC oscillators, a fixed or reference one and a search one. The coil of the search oscillator is located in close proximity to the ground. When a metal object is close, it changes the inductance of the coil, changing the frequency the search oscillator works at. In this case, both oscillators work around 200 kHz. Both signals are added together, and that results in an AM signal, which can be demodulated. The audio tone resultant happens to be the difference of the two frequencies. This way, changes in frequency of the search oscillator can be noticed as the sound frequency changes. Testing and modification of the original design. Notice that AM signal and its demodulation can be seen on the scope: The frequency adjustment was modified and an audio amplifier was added. Here is the schematic for my version. Capacitor values are marked as they appear on the physical com...