Tuesday, May 24, 2016

Pellet burner controller code

My pellet burner controller code become open source. The code is in programming language C. I post it at the GitHub: https://github.com/canji/Pellet-burner-controller

Comments in the code are on the Serbian. I don't have time now to translate it. If someone need help understand the code, please contact me

I have big omission in my previous post about pellet burner controller. Pellet burner expert which I cooperated is Miodrag Cvejin. Big thanks for him!

Tuesday, May 17, 2016

Diesel generators

Sometimes at my job I work with diesel electric generators. As a testing engineer I perform inspection and test of it. For testing we use a mobile load bank. Our mobile load bank is just resistive and it looks like giant heater. It has bank of heater and fan. Its maximum load is 1MW. 

Diesel generators aren’t complex machines. They have two parts. One is a diesel engine and second is an electric generator. 

From electrics and electronics stuffs a diesel engine has lots of sensors. The most typical is for an oil pressure and a temperature, a coolant level and a temperature and a pick-up for speed. 

A generator gives the sin wave output voltage with specified voltage amplitude and frequency. In our case this is always 400V between phases and 50Hz. 

The generator frequency depends from a diesel engine speed. We control frequency by controlling the diesel engine speed. Because most of generators are four pole electric machines we need 1500 rpm for frequency of 50Hz. 

Most of diesel generators that we test are older than me. This old diesel engines have fixed fuel injection. Because of this its frequency varies with changing a load. As we gain load the frequency goes down. Most of old diesel generators can take no more than 80% of load and for this load frequency goes down for 1Hz. 

New generation of diesel generators has an electric control fuel injection and them frequency is perfect 50Hz all the time. Just when we apply high jump of load the frequency changes a little. This change depends from a PID controller for speed control. When we apply high load, for example form 0% to 75%, frequency goes down because of suddenly high load. Depends of a PID controller it can be slow comeback to the 50Hz without over frequency or quick come back to the 50Hz with some peak of over frequency. 

For a generator voltage control a generator has voltage regulator. A generator is synchronous electrical machine and its output voltage depends from a magnetic field in a rotor. Voltage regulator is uses to control that magnetic field. It works as controlled AC DC converter. With DC voltage output it controls magnetic field in a rotor. 

Also as frequency, old diesel generators has fixed voltage regulator. Output voltage changes with changing frequency. In some case voltage goes down when frequency goes down and in some cases are oppositely. 

New generation of diesel generators has an electric controlled voltage regulator and output voltage is always perfect 400V. 

I reconstructed one voltage regulator and this interesting electronic story will be in the next post. 

Wednesday, May 11, 2016

Typical holiday

Adam and Milica

Last two weeks I was in the Brus. This is typical holiday for my family. The Brus is hometown of my wife Milica. This is a small town near Serbian famous mountain Kopaonik. There we always have a nice time.

My favorite sport activity is road bike climbing to the Kopaonik. There are four roads for climbing to the Kopaonik. I think every climb is the first category in cycling. I try every of four roads and my favorite climb is through “Kriva Reka” village. 

There are many interesting places near the Brus. Mountain Goc is also beautiful. Food is excellent there. In a future I will write more detailed about the Brus.

Top of Kopaonik mountain

Some pictures from previous holidays:  

My car preparing for the trip

Top of the hill above the Brus 

Bike climbing on the Kopaonik through "Kriva Reka" village

The old castle "Koznik" near the Brus

Monday, April 25, 2016

PH-PT click

I almost finish PH-PT click for the “MikroElektronika” company. This click board is interface for a PH electrode and a PT temperature probe. It contains two integrate circuits. One is the analog interface for a PH electrode and a PT probe LMP91200 and the second is analog-digital converter MCP3428. For communication with a microcontroller the PH-PT click board uses SPI for setting the analog interface LMP91200 and I2C for communication with the ADC MCP3428.

Reading PT probe is tested and it works fine. I’ll buy PH electrode and will test second functionality. 

I made a small mistake with voltage reference and I have to do a review. This would be just a little change in the PCB. There are too much administrative tasks at my job and my brain gets rusty. I must work more on a hardware and software.  

More about the “MikeoElektronika” click boards you can find on www.microe.com/click/.

Wednesday, April 20, 2016


Pellet burner controller PCB in KiCad

KiCad is software for electronics design. The programs handle Schematic Capture and PCB Layout with Gerber output. 

KiCad is free software, open source. It runs on Windows, Linux and OS X. 

I like KiCad. I used it to design the Pellet burner controller PCB and plan use it for some future projects. 

KiCad is simple and comfortable to using and I recommend it to everyone. 

Saturday, April 9, 2016

Demand power

A demand power can be found at an electrical bill in an industry. Also, it can be found at an electrical bill in a household. In the industry the demand power is measured, and in a household this is just one more mysterious budget item at the electrical bill. 

An electric meter in the industry measures average power on the define time interval. The maximum average power on the define time interval in one month is demand power for that month. The define time interval can be from 10 minutes to 30 minutes. In Serbia this is 15 minutes. A new electric meter the 15 minutes interval synchronizes with a clock. 

If we in the industry take care about the demand power, we can have lower electrical bill. The goal is to have more uniformly electrical power consumption. If we have needs for peaks in electrical power consumption, we must arrange peaks in different 15 minutes time intervals. I have tried to investigate how to lower demand power at my job.

Wednesday, March 30, 2016

Linux is my biggest weakness

Sometimes I look job ads. I want to see what kind of engineer companies need. For many embedded software engineer job positions the Linux is necessary. Embedded Linux is most common operating system for embedded devices.

I have never worked with the Linux. Once I installed the Fedora Linux on my desktop PC but I didn’t use it a lot.

Now I plant to learn the Linux. I think this wouldn’t be hard. I will buy the Raspberry Pi Zero. This small computer for 5 dollars can be interesting base for many embedded projects. It has the Linux. I think the Linux on Raspberry Pi Zero would be too much robust for some real time embedded systems. I plan to investigate how this Linux distribution can be reduced and become more reliable for some embedded applications.

Some interesting sites and texts about Linux: