Author Archives: Xose Pérez

About Xose Pérez

I've spent half my life working with computers creating virtual products, now I've moved to the physical part of it, much more fun!

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PCB fabs

A few years ago (not many) I used to burn copper plates using acetic acid, a.k.a. vinegar. I was somewhat concerned about using stronger acids so it was OK to use another acid, even if it was soooo sloooow. If you were patient you could get to have decent boards using 50mil traces (or even thinner). But it required keeping a good temperature on the copper bath and regulating the ratio vinegar/hydrogen peroxide continuously, adding a little salt from time to time to speed things up.

The etchant biting the copper

The vinegar biting the copper

One day I saw an article about cheap Chinese PCB fabs (I think it was DirtyPCB by Dangerous Prototypes) and I decided to design my own board and send it to fab. I used Eagle (I still use it although I’m learning KICAD) and the learning process was significant. But at the end I managed to get something. I learned to use copper pours, to correctly label the board, to create my own parts, to avoid auto-route, to use design rules and create gerbers,…

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And over time I have tested different fabs. I’m not an expert by any means but I wanted to write a bit about them here. The basic order I usually do is a 10 units, under 50x50mm board, 1.6mm thick, 1oz copper and HASL Lead Free due to RoHS rules in the EU. The prices and options below are based on these settings.

One more thing. I reckon these suppliers are good enough in most cases for small batches, testing boards or DIY projects. Some EE are concerned about the quality of the boards and they prefer EU-based (or US-based) fabs. I cannot offer a good reason to use these manufacturers here or to not use them in professional/industrial projects.

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Yet another WiFi light bulb

Eight months ago I reviewed and hacked the AiLight WiFi light bulb by AiThinker. By the time there was a number of people doing the same because of a key reason: it sports an ESP8266 microcontroller and it is based on the OpenLight by Noduino, that had already provided open source code for the LED driver inside, the MY9291.

Let time pass and I was doing the same with the Sonoff B1 light bulb by Itead Studio. That was two months ago and the conclusion was that the AiLight is brighter the the B1 but the lacks warm white channel the Sonoff bulb has.

And now here I have yet another WiFi light bulb, the Arilux E27 Smart Bulb. It looks pretty much like the other two, same shape, same microcontroller, same driver, but different base again and most important: different LEDs. So how does this one compare to the other ones?

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Sonoff B1, lights and shades

Six months ago I was reviewing the AiThinker AiLight, a great looking light bulb with an embedded ESP8266EX microcontroller, driven by a MY9291 LED driver. Just before summer IteadStudio released it’s Sonoff B1 [Itead.cc] light bulb, heavily inspired (probably same manufacturer) by the AiLight, at least on the design.

Now that IteadStudio has become popular between the home automation community you can also find the Sonoff B1 on global marketplaces like Ebay or Aliexpress for around 13€.

A closer look at the B1 uncovers some important differences. But before going deeper into the details let me first say that this post will probably look more like a review, at least more than I use to write. And second, yes: ESPurna supports the Sonoff B1 🙂

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Connected power meter

A few weeks ago a user came with a request to add support in ESPurna to a power meter that had been hacked by Karl Hagström. It is a very cheap chinese power meter with plenty of room on the inside, enough to house an ESP8266 module and a DC/DC power supply and the main IC protocol had been reverse engeneered. There even was a repository by the Harringay Maker Space with sample code for an arduino compatible platform.

I found it really interesting so I jumped in and ordered two of them (for 25,20 euros in total). Unfortunately the seller I bought it from has ran out of them. But you can still find them on the usual market places, like these ones [Ebay] or (also with non-EU variants) these ones [Aliexpress].

When I received them I quicky unscrewed the enclosure of one of them and… wow, it looked slightly different than that on Karl’s post but also different from the one the people at Harringay Maker Space had worked with.

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I went back and forth and I noticed the hack was almost 2 years old and the board was clearly different: different version (unlabelled on Karl’s pictures, version 2014-04-28 on Harringay’s power meter and 2016-12-18 on mine), different board layout with a different connector between the power meter board and the display (7 wires on theirs, 6 on mine). But the most important difference was the main power meter IC. Karl had reverse engineered the ECH1560 on his power meter, a 24pin SOP package (on the back on his device, on the front in Herringay’s power meter). Mine was only 16pin…

p1240274sI had to decipher the IC mark using parts from both devices since the manufacturer had crossed out the marks (they don’t want us to hack it or what?). Finally my best guess was V9261F. I quicky googled it and… bingo!

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Hacking the Sonoff RF Bridge 433

Itead Studio has been releasing interesting gadgets for the Home Automation community based on a low price tag and extreme hackability. You can google “sonoff” (the main brand for Itead Studio home automation devices) to get more than a million hits, including official pages, reviews and lots of hacks. The ubiquitous ESP8266 (or its sibling ESP8285) is the core of all those devices, using WiFi instead of the traditional RF messages, replacing a remote with mobile apps or voice commands. But also, using custom firmwares like ESPurna, technologies and solutions like MQTT, Node-RED or Home Assistant. But one of the latests devices from the chinese firm tries to bridge the gap between those two technologies: the Sonoff RF Bridge 433.

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