ZMAi-90 (or SMTONOFF WDS688) DIN rail meter/switch - more details on GPIOs and configuration

As an update to the previous post where I have shared the details on how to "Tasmotize" this device, I am adding more detail on what is the physical assignement of GPIO pins from the ESP8266, to other components in this device.

Given the pins from the ESP8266 microcontroller that are exposed in its breakout board (which in turn is SMD soldered to the main PCB):

Attempting to reverse engineer a home automation oriented smart-meter - Part 1

In my quest to make my house smarter, but still looking forward to keep having control over it, I have been doing some additions which I plan to further document here, in the short term.

In the meantime I thought it would be more relevant to share my findings in regard to a device a bit more "exhotic" than the Sonoff boxes we are all used to. This device is a sort of a miniature smartmeter that fits in a DIN rail next to the circuit breakers.

Just like the Sonoff modules, it also pairs with your WLAN, and connects to a cloud service. Instead of the eWeLink cloud to which Sonoff devices connect to, in this case it connects to another relatively popular cloud service called Tuya.

DSLR Intervalometer - Source code made available in GitHub

For those who remember my work back in the days with implementing an intervalometer for Nikon cameras (yes, in spite of it being rather simple to implement in the camera firmware itself, these larger brands prefer to classify such a feature as premium and make it available only in more expensive DSLRs), I have detailed in the following post, the solution that I have put together:

https://www.creationfactory.co/2012/03/timelapse-intervalometer-technology.html

Peltier-based dehumidifier

This simple apparatus is a particularly interesting way of demonstrating the principle behind the common household dehumidifier:

The big difference however, lies in the way the low temperature (required for the condensation of the water vapour) is achieved.

Repurposing an old Android Phone

I had an old Samsung Galaxy Y (GT-S5360) which the previous user didn't particularly enjoy for its performance and replaced with a fancier, newer model. With no obvious use to give to the device, I decided to repurpose it for building some kind of a remote monitoring/observation station, and try to find out how it stands out against the harsh outside environment.

While not attempting to simply put the device outside, directly exposed to the sun, rain and extremes of temperature, I made several customizations to better prepare the smartphone turned into a monitoring station.

The first thing I wanted was to have it entirely self-sustainable. As such I bought a 10 watt photovoltaic panel to harvest the energy required by the device:

Again with the SDR (Software Defined Radio) craze

After I bought my first RTL-SDR dongle (regarding which I made this post covering APT satellite (weather) image reception: http://creationfactory.blogspot.pt/2013/03/receiving-weather-satellite-images-with.html ), it's been sitting on the bench without much use. More recently I found extra stuff that could be interesting to take a look at, such as ADS-B reception (decoding commercial aircraft transponder signals) and less earthly things such as a doing some radio-astronomy, which includes for example trying to detect the 1420 MHz hydrogen line RF signal emitted from within our galaxy (it's a very exact frequency almost as accurate as our atomic clocks).

http://www.rtl-sdr.com/low-cost-hydrogen-line-telescope-using-rtl-sdr/

Teardown of a laser printer

In this age of mass consumption  and programmed obsolescence, it is not surprising that a few years after you shell out money for a printer, the availability of its consumables starts to decrease, followed by an increase of the associated price.

Custom made BEC

BEC's, which is short for Battery Eliminator Circuit is a fancy RC hobby term for a DC-DC converter that steps down the voltage to a given value used for example by servos and control electronics such as radio gear and flight controllers.

In the market there are two main types, most of which convert from a higher voltage to 5-6 Volts DC. These can either be of the linear type, or switching mode. The first is the simplest, where a simple linear regulator is used to drop the voltage to a constant value at the output. These tend to be very low noise steady sources of voltage, but have the disadvantage of being quite inefficient, getting worse the higher the input-output voltage differential. A considerable amount of energy is wasted in the form of heat.

Induction Stove

Some days ago my father asked me to check if I could repair this single element induction stove. I disassembled the device to inspect its inner workings. I was a bit curious because I have never taken apart this kind of apparatus.

Busy quadcopter setup weekend

With the arrival of some of the parts I have been waiting for, more work accumulated with the finishing of my 2nd quadcopter. The parts were the landing gear and the quadruple ESC: The landing gear arrived with all the necessary parts as expected, including the lower crossing bar and the foam rods. The bar and other rods are all made of carbon fiber. The 4 support rings (for attaching to the frame) all had a rubber ring which helps to further dampen the vibration to additional items such as a camera:

Reflash the ESCs

Multicopters require a tight control loop for all the motors as part of their ability to perform stable flight. A basic requirement for an efficient closed loop PID system is that it has a high enough sample rate and fast response to error input when the knowledge about the system is minimal. Until recently most ESCs were designed for airplane and helicopter applications, where gradual response to input is desirable for saving the gears against abrupt torque variations. In quadcopters, direct driving of the propeller is normally the case (and as such mechanical wear is not much of an issue), and as explained, quick response to throttle input is required for good PID response.

Gathering with fellow pilots and Multicopter improvements

Most of the time I have been a lone rider in this hobby, having started from scratch on my own, since the traditional helicopters back in 2009. I would occasionally go to local air fields and try to mix in with seasoned RC airplane and helicopter pilots. But the environment would not always be too friendly, with the fixed wing guys not enjoying much the flying grass cutters.

Powerwheels RC conversion

I soon noticed my 20 month daughter affinity to vehicles. I wanted to give her one where she could sit and enjoy the ride, but currently most powered vehicles for infants require they are able to reach the throttle pedal and properly handle the steering wheel. So I figured out the best way would be to go remote controlled. As I already had done previous projects involving RC gear, it would be piece of cake to turn a regular electric car into a large scale RC car where a small kid could sit inside.

Power Supply Refactoring - finishing the details

In spite of already being a working device, there were aspects that like I explained in the previous post, required some attention. One of the major fixes was the voltage drift. This was caused by the 5 K potentiometer used to set the voltage end point. It was too large (the sweet spot of my setup was around 500 Ohms), which besides making it difficult to adjust, caused temperature induced resistance drift to be too large, causing an increase of around 200 mV from the initial voltage once the temperature settled.

Power Supply Refactoring - closing the hood

After many hours of work I finally can say it's done. Even though I don't consider it the perfect work, I can definitively consider it a major improvement in respect to the previous version of the PSU:

Before:

Power Supply Refactoring - part 5

Prior to assembling the definitive power supply circuit board (i.e. the main electronics featuring the LM723) I took the time to set it up on a breadboard. Before that I finished the board containing only the large components such as the filter capacitors and the high wattage resistors (current shunt used by the regulator chip to sense the current across the power rail, and a bleed resistor for the output capacitor):

Power Supply Refactoring - part 4

Another weekend have passed, and along with it a few more results as I slowly but steadily walk towards completion of the project. The digital voltmeter/ammeter displays have still not arrived from China. This is the last piece of hardware missing. Adding time to the equation and all the elements necessary to complete the project are available.

Power Supply Refactoring - part 3

Bit by bit the work is advancing. I have finally defined the schematic diagram from the entire power supply circuit. It includes also the PIC based fan control.

Power Supply Refactoring - part 2

The parts from Mouser have arrived (was pretty quick..wouldn't the shipment have been taken care of by FedEx):

Power Suppy Refactoring

In this previous post I had the chance to present and tear down my old custom-made power supply. It worked flawlessly for about 10 years. I decided to buy a new linear lab power supply because I needed something better with more features such as constant current operation and digital display of both voltage and current.