NOAA APT Satellite - Night time weather pictures!

My first and accidental attempt at receiving images from a weather satellite was surprisingly very succesful. However as I only started capturing the RF signal late in the satellite pass, it was only possible to retrieve a small portion of the transmitted image.

AMIRO - Autonomous MIni ROver

In a recent past I have been very active blogging about this project, which have occupied a portion of my free time in a rather pleasurable manner. After a period of pause I thought of bringing this project back to life, but not without providing an overview of what have been done.

Teardown of one of my first electronics projects: a PSU

This have been for about ten years a loyal companion in my electronics projects. And greater than that the fact that it was itself one of my first projects. After that time it still works like a charm.However I thought it was time to replace it with a PSU providing more functionality such as constant current and digital displays.

Modded for long range and glitch free communication

After assembling my quadcopter, one major issue I stumbled upon was the (lack of) quality of my radio system.

Multicopter Madness

R/C airplane modelling exists for several decades, but with late improvements and reduced cost in microelectronics, energy storage, and RF communications, products in this domain have suffered a significant improvement in quality and innovation.

Sensing the Heart Beat

Among the most basic forms of biometric data we may collect from ourselves is the heart beat.Wether to control our body response to sports activities, keep track of our health or to observe involuntary response to external interaction, this is one of the important parameters that is collected by physicians, and specialists of a multitude of health-related areas. What I am describing in this post is just the implementation of one of simplest forms of obtaining a waveform that represents the heart beat of an individual.

Simulation mode for the Geiger Counter

While obtaining samples of materials radioactive above background is not an easy task (fortunately for the sake of human health), I had to find a way of testing the dose measurement algorithm in a different way. As I have explained in a previous post, the device is divided in two modules: a UI module, and the detector device. Each has its own digital logic, and communicate with each other through an I2C bus. As such creating a simulation mode would be a simple mather of programming a new function in the detector that would allow randomly spaced pulses to be generated, instead of being triggered by the Geiger tube. This have been done simply by using the Atmel standard libraries random() function. Using the interrupt generated by the watchdog timer overflow, the following code is executed periodically:

The timelapse intervalometer - the technology behind the device

With the results having been posted in a previous post, it is now time to flesh through the details that led to the creation of this simple yet useful device.

I started with the optimism that my Fujifilm S9600 camera would have some form of remote control possibillity other than the mechanical shutter release that is supported in the shutter button itself.

Time lapse shooting - moving into more professional results...

While the first videos seemed pretty cool in spite its mediocre quality (maybe because of the time domain wonder of perceiving things that we normally wouldn't given the different time scale we live in), now I had to move one step further.

The idea was to use a better camera, one offering photographic quality in every single frame.

LENA - Now featuring dose measurement

The DOSE feature discussed in the previous post is now done. Taking into account the GM tube characteristics, a realistic measure of radiation dose in uSv/hour is now being calculated, based on the single event rate. From the information obtained on the internet regarding the SI-39G tube, the value of 0.00049 uSv per pulse was taken into account for the calculation of the dose.

Additionally, another mode usually found in most Geiger counters and dosimeters is the CPM (Counts Per Minute) mode. It provides a relative measure (that is of course GM tube dependent) of the radiation exposure, based on the ammount of particles detected by the tube. In this case these can be either Beta particles with more penetrating energy, and Gamma photons. Alpha particles cannot be detected by this particular tube (the SI-39G).

LENA - The Geiger Counter that was finally made portable!

With the Geiger Muller tube module having been posted in a previous post, namely here, another important development was missing. While fully functional at that time as a sensor device which could readily be interfaced with via I2C, or having the pulses be directly picked up via a dedicated TTL signal, by itself the device could not be carried on the field and be expected to operate without additional hardware.

Me and my employer in the Elektor magazine!

In late september (the 29th to be more exact) PDMFC's online store Microsensus was officially launched. This event gathered a lot of people from the portuguese microelectronics community. And is needless to say it was a success. It was an opportunity to expose our work to many relevant people, from universities to SME's and large companies. The event also captured the media attention, in particular the portuguese version of the Elektor magazine. I had the chance to talk about the products and what motivated PDMFC to enroll in the hardware business.

As it was published, it felt good to see my face and the rest of the team printed in the pages of a magazine that for me and many people in the electronics world is legendary for its articles and its role at stimulating young minds towards creativity through the use of technological artifacts.

I2C Geiger Counter

With nuke plants operating under questionable technical safety, natural events threatening humans and their dangerous energy production artifacts, and other humans disseminating fear through nuclear sovereignty upon the rest of the world, we came a long way from the happy ignorance of distant decades.

Baby monitor

While preparing to be a father for the first time, I have found most baby products to be more expensive than would otherwise be desirable, given its ephemeral usefulness. Considering the full blown economical crisis that we face today, spending copious ammounts of money in things that soon become useless, seems a little too light headed and perhaps irresponsible.

AMIRO - more enhancements.

After a few months of posting abstinence here are some fresh new things to show this summer. The android application has been dramatically improved with new features and better visual layout. Additionally a portable video screen have been build, in this case sporting a 4.3" tft panel, a 1.2 GHz analog video receiver (originally used in a fixed manner), a LiPo battery, and a custom made battery voltage warning circuit (yes, LiPo batteries are particularly susceptible to damage under deep discharge situations).

Controlling Amiro (the name I have baptized the car) from an Android phone (HTC Desire)

While the Java PC application is useful for testing and controlling the robotic car while sitting in a chair, for on the field fun a more practical solution had to adopted. So using a popular platform that Android is, I decided to port the (Java Swing) application I already had, to run on any Android phone with a accelerometers and a Wifi connection. As the car behaves like an access point, all it is necessary is to associate the phone to it, and run the application.

Just about as fun as it is to drive it, coding the client in Android was quick an fun experience.
The interface had to contain just the essential elements. While the target hardware has abundant resolution (480x800), like in any mobile platform, screen real estate is always a concern. As such I had to economize on the components to be displayed. The result was a relatively simple UI:

Quadrature Encoder

One of the essential things an autonomous rover must have (which mine didn't had) is one or more quadrature encoders. In fact even some non-autonomous vehicles have these devices. Most regular cars these days feature this type of sensor as part of the ABS system (see http://en.wikipedia.org/wiki/Anti-lock_braking_system). Very reliable and high-resolution sensors can be found in these (featuring 90 steps or more).

For this autonomous rover I found that 16 steps would be the bare minimum, and easy to implement with common components.

As I didn't want to modify the RC car itself (drill holes, cut parts, etc), I looked for a solution that would minimize the impact on the car. As such I found that a good option would be to use the inner ring of the wheel as a surface for sticking an encoder band. This band has 16 steps, and looks like this:

Now remotely controlled via IP

After some hobby time spenditure, the result meets the expectations. While it is a functional and simple (and a good fallback solution), controlling the car via a regular RC radio is not the most interesting scenario. Having a device that is mostly digital, being controlled by an analog receiver isn't quite the nicest thing one would want to showcase. With that in mind, and taking into account that all the necessary hardware was already there and working, I have decided to take a little bit of time implementing the necessary components to be able to control the car from a remote peer in a wifi network. As such all I had was to:

Booster circuitry up and running

Running digital equipment has the drawback of requiring tight voltage ranges in order to operate. In the case of my robot, I had the need for powering the Fonera 2100 from a pack of 4 AA batteries. While the batteries can deliver 4.8 Volts once fully charged (which is barely sufficient to power this wireless appliance directly), once the voltage drops further, the Fonera ceasses to operate. In this situation the batteries still have remaining energy that is not possible to use.

Drastic Improvement: new Mobile Platform

After a lot of stress tests with the original platform, it was time for something better. The original platform was no more than a toy RC car (entirely made of plastic) with some hobby RC parts on top of if, such as refurbished steering system (with a real servo) and a home made ESC (Electronic Speed Controller) for the original toy car motor. During a demonstration with my 4 year old nephew, showing him how fast the roving robot would go in an open area, suddenly something happened: it started running full speed, totally out of control, both forward and backward (in my mind I immediately tought one of the ESC FET's had fried). I rushed to grab it, and suddenly smoke started coming out of the motor. Worried about the LiPo battery, with the motor still running and smoking, I centered all effort in disconnecting the battery. My nephew started to cry with the stange situation. After making sure no fire would occur, I had a confused infant to comfort.