I occasionally need to compare two versions of a diagram or a screenshot to see what actually changed. There are free websites for this, but they all want the images uploaded to their server, and the diffs they produce are…
Image diff tool
DEV.BG tech talk: Intelligent Synergy: Heat Pump, PV & Home Assistant
I was invited to do a tech talk by DEV.BG a few weeks ago, and I chose to discuss my recent heat pump upgrade project, the integration with the existing PV system, and Home Assistant. The tech talk was in…
Thoughts on structuring a productive software development team
I recently spoke with a friend of mine, who is now a software development team manager in a Fortune 500 listed company. He shared with me that his managed teams work using agile methodologies and consist only of software developers.…
Using mTLS to secure IoT solutions
While delivering on the promise of streamlined efficiencies and operational insights, smart IoT devices also present a new and more widespread threat to users and personal data. No one really needs reminding of the security implications of IoT. Think of…
People-Tools-Processes
As an IT team manager, I am responsible for forming highly engaged and efficient teams. Building an agile team requires a fine balance of skilled and motivated people, fine-tuned processes and proper tool selection.Put too much focus on people and…
DEV.BG tech talk #3
I did a tech talk about my ESP32 based IoT control hub project on Feb 5th, 2019 at Work & Share Coworking Space Sofia. Over 100 people signed up for the event organized by DEV.BG, it was a pleasant surprise…
Thoughts on time/date management on IoT nodes
Accurate time/date information is crucial for the correct operation of IoT nodes. From a security perspective, time/date information is necessary to perform SSL certificate validations. If your embedded device’s clock isn’t accurate, you can’t ensure the presented server certificate hasn’t…
DEV.BG tech talk
I will be doing a tech talk on topic “Hardware and firmware considerations when designing low power battery operated wireless edge nodes for Internet of Things applications” at an event organized by DEV.BG. Join me on April 18th, starting 19:15…
Where are the IT jobs in Sofia located?
I had a chat with a colleague the other day, discussing his property purchasing plans. He shared that the proximity to workplace is important for him. Planning in the long term, he asked me what districts of Sofia would be…
proSmart
I have been busy starting up an exciting new project the last few months, a joint effort with a team of highly enthusiastic, hands-on, broadly skilled contributors with the goal to design and develop IoT home/industrial automation solutions. Together, we established…
Auto DST adjustment
We are close to that time of the year when Daylight Saving Time (DST) starts. It is intended to save on energy use, however, studies have found this to be questionable, even contrary – energy use increases in some cases. The change itself…
Local hostname for connected devices
Now that we have connected our project to the local network, we are immediately faced with another challenge: how can we reach it? Using WPS/SmartConfig means we force the unit into DHCP settings mode, IP address is auto assigned by the router in…
The initial setup problem
The typical end-user of your IoT products wants them up and running fast, with minimum hassle once they bring them home. They don’t want to be presented with initial configuration mechanisms/options they don’t understand, and their enthusiasm quickly diminishes if…
My own cloud based version control tool
There is no second opinion about the importance of version control, it is a must-have for any software project. The option for reversibility, concurrency and history of code edits is what makes it so crucial. I’ve been using mostly GitHub for…
Some thoughts on security in terms of IoT
Connected devices and sensors are the fastest growing sources of data. Billions of records are being generated daily around the globe and data transported across networks to be consumed where needed. Security of data in transit or at still in that…
Physical vs Virtual
The Raspberry Pi, a $35 credit card sized computer, is a popular choice for home automation projects. I am running few of those at home myself. But what is the true cost of these, is the advertised cost of $35 really all…
Google video tech-talk hangout anyone?
I’ve been meaning to hold a video Google hangout session on IoT topics for some time now, how about giving it a try? I imagine it as informal 1 hr tech-talk with the following structure 35 min presentation of a…
I am a @quantifiedself
I accidentally landed on a site called ‘quantified self’ last month and immediately realized I am doing lots of lifelogging myself. I track my commutes, log my weight, my body temperature when sick, my hot water usage habits, visitors to…
Thoughts on AVR ADC accuracy
I was thinking about the accuracy of the battery measurements the other day, are these accurate or not? I measured the battery using Fluke 27 multimeter and compared that to the readout using the internal bangap method and found a small difference.…
Non-contact AC detection
Alex from insideGadgets had an interesting project last year on non-contact AC detection and I wanted to try it out and learn how it works. He hooked one leg of a 1M ohm resistor to GND and a wire to…
DHT22 accuracy test part 2/2
I have measured the relative humidity as per my set up, and got steady readouts exactly in the 75% area as expected: DHT22 Library Demo Requesting data…Got Data 25.50C 75.20% Integer-only reading: Temperature 25.5 C, Humidity 75.2 % RH Requesting…
DHT22 accuracy test part 1
I have been boggled for a while about the Relative Humidity data that I gather, I get some higher than expected reading. I blogged about this in this post and @Dimitrios suggested in the comments that my box my be…
Cheap DIY power monitor
My father asked me to create a standalone power monitor for him, he’d like attach it to some appliance and see its momentary and accumulated over time power consumption. Using OpenEnergyMonitor’s resources that was an easy task to do. I…
Dirt Cheap Low Power Wireless Sensor Node using nRF24L01+ 2.4GHz
I have mentioned before, that I have purchased couple nRF24L01+ units from eBay for the stunning $3 with delivery included. I decided to make some cheap tests this time, so went for a veroboard prototype. I got two blank DIP…
Cheap USB to 3.3V TTL FTDI Cable goes to the trash bin
I have a cheap USB to 3.3V TTL FTDI Cable that I bought on Ebay. It has been giving me some troubles ever since I got it, burned couple RFM12B modules along the way. I decided to hook it to…
Scope screenshots
One of the cool things about having a digital scope is that you can take screenshots and post them in blogs :). I wanted to check how a Funky v2 was behaving, so hooked one to measure its current consumption…
Oscilloscope
I have finally decided to get myself an oscilloscope, my choice ended up to be a Rigol DS1052E. The model seems to be pretty popular, and for a price tag of 309 EUR with delivery, I could no longer resist.…
Soil moisture sensing revisited
I have previously created a DIY soil moisture sensor, but wiring it required couple resistors. I was recently reading a post by JCW on using a light sensor and figured I could simplify my setup using the same basic idea…
RFM12B End of Life
EDIT March 2015: [It has been two years since this post, and the RFM12B is still widely available. I guess the rumors at that time were exaggerated widely.] There has been bad news for the RFM12B ecosystem last week, namely the…
Wallpaper prank
I wish I did this for April 1st, but here is it anyway 🙂 I wanted to test out the HID keyboard features of the Arduino Leonardo compatible Funky v2, so during my research on the subject I accidentally stumbled…
Toying with a 1.8″ TFT LCD display
I got myself a 1.8″ TFT LCD display from ebay, attracted by the low price. The display also has a SD card slot. It comes without any documentation and you are presented the joys of figuring out how to drive it…
Raspberry Pi as IP webcam
I noticed this Instructable the other day and had to try it since I had an old USB web cam laying around. I found that the instructions contained some inaccuracies, here are my steps: sudo apt-get install motion sudo nano /etc/motion/motion.conf Locate…