Category Archives: Electronics

Cleaning Club3D Radeon HD7870 graphics card from my PC

My graphics card started making some weird noises. After investigation (opening the case, finding a flashlight :D) I found out that the problem was with dust built-up in fan area. After taking care of it I decided to replace the thermal paste. This is how this video was born ūüôā

For cleaning I am using 93% denatured alcohol.
Thermal paste is Arctic Silver 5 (

Epic Re:load v2 review


Re:load v2 is an adjustable constant-current load.

A really cool thing is that it is self powered and can go to 3.3v keeping it’s current limiting capabilities. I went for the 0-6 Amp version since the price difference is minuscule and it seemed more useful in the future. According to the documentation it can handle 20 W or more with the larger heat-sink. Who does not like having some extra leeway…

Please see the full review as well as build process in my YouTube video:

Project BAC v.1.1


This post is about a project that took ages to built and I manage to loose in an unfortunate circumstances…

I always wanted to build a clock. And this is what came up…

The Idea

Create a modular clock that has interchangeable displays.

The Execution

Main controller



The main module for the clock is an ATmega328 microcontroller with a DS1307 Real Time Clock. The LCD displays current date and temperature as well as shows the setup menu.

Interaction with the clock is done by one rotary encoder that has a built-in push button. The state diagram for the menu can be found below.


Display Controllers


Time display (described below) is controller by a series of 74HC595 shift registers. Since there is a need for two digits per segment (by segment I mean hours, minutes and seconds) there are 6 of them in total connected in series. To update the time display I have to shift out the current state of the hours, minutes and seconds every second. Since the update rate is relatively slow no stress is applied to the microcontroller and it can do other tasks like displaying temperature readings, etc.

Time display

ImageTime is displayed on a self-built 7 segment displays. There are 3 LED’s for the horizontal axis and 4 for the vertical one. By testing various combinations I found that this setup was the most appealing to my eyes. LED’s in a segment are connected in parallel and routed to the input connector at the bottom of the board (color-coded cable in the photo). The only problem I had with the displays was that they were really bright even on the lowest brightness setting (that can adjusted through the menu). To mitigate this problem I added some plexiglass that I painted white to¬†diffuse¬†the light a bit. Note to myself for the future projects: do not use clear LED’s for such applications…

More photosImage



A short clip showing the testing of the time display


I had a lot of fun working on this project. It was a really nice learning experience and I am planning on rebuilding the project in the future with some improvements.

Audio switcher

I’ve been looking for a while now to find a way to switch between multiple audio sources and output them on my speaker system.

Finally, I decided that the simple way is the best way :), so there’s what I came up with.

This is a 3P4T switch with four 3.5mm stereo female audio jacks acting as input and a 3.5mm stereo female audio jack that outputs the selected channel to the speakers. The knob points to the channel that is selected. Audio sources in this photo is my main PC and a Media laptop used for watching videos. There’s still two unused inputs left for connecting my phone/tablet/etc.

Now some photos from the build process:

I’ve spend approx. 100 DKK (17.5USD) for the parts (box, switch, knob, audio cable) that I did not have in my spare parts bin, but also had lots of fun building it, so, to my mind, it was worth the price.

ST7735 1.8″ TFT Dispay: SPI vs General connection


I got a ST7735 based lcd from ebay and decided to play with it a bit.


  • Arduino UNO
  • 1.8″ TFT LCD from ebay
  • Some jumper cables


All the guidelines for connecting the LCD to the Arduino can be found here:¬†, but there is one thing to note. In the tutorial there is a pin called¬†“dc” (Data/Command) (thanks to sza2)¬†(I am not sure what that stands for)¬†, but on my LCD it’s named ¬†“RS”¬†(register select). So, to make it work, just ignore the difference in naming.

Display driver library:

And the required graphics library:

I am using the demo-sketches from the AdafruitST7735\examples\:

  • graphicstest
  • graphicstest_highspeed

Comparison itself

In the video you can see the communication protocol speed comparison.


SPI is the way to go ūüôā

Project LIBMS: Li-Ion Battery Monitoring System

Creative Commons LicenseLIBMS by Vaidas Sirtautas is licensed under a
Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
 Permissions beyond the scope of this license may be available


or you can watch in HD on Youtube.


Let’s start with a problem…

In order to have my phone as well as my BlueTooth audio headset working I had to carry two different chargers to workplace.¬† Moreover, I needed to find an unused socket to plug them in. And that’s really annoying…


I could see two possible solutions:

  • Buy a charger that uses batteries and provides 5V to charge my devices
  • Build one of my own

And, of course, I went with choice #2. I had some Lithium Ion batteries lying around. And this was the starting point of LIBMS.


It would be crazy to just power devices through some voltage regulator. LiIon cells do not like to be discharged below 3V and without some additional circuitry it was impossible to check whether they were OK to continue providing power to the devices. (Well, I could carry a multimeter and measure each of them from time to time, but that would be crazy :))

I found some IC’s that are capable of monitoring LiIon batteries, but where’s the fun in that…

I had some Atmega328 chips laying around. They have a 6 channel 10-bit ADC (there is actually only one ADC, but built-in multiplexer expands the inputs to 6). Awesome.


I connected 3 of the batteries in series and then that block with another block of three batteries in parallel. V1..V6 show my tap points that are used to measure each cells voltage. E.g.

  • V(G2) = V2 – V1
  • V(G3) = V6 – V(G2)
  • V(G6) = V6 – V(G5)

Batteries are connected this way

Voltage regulators

At the beginning of this project I had some problems with voltage regulation. I powered the microcontroller (uC) directly from the main voltage regulator (LM338), but when a device was connected that requires a lot of current the voltage suddenly dropped and uC restarted. Not good…

I solved this problem by introducing secondary LM7805 voltage regulator that is used to power the uC and LM338 takes care of the USB ports. Using this structure provided me with a cool way for controlling the USB ports from uC.

Browsing through the LM338’s data-sheet I found an example where the regulator can be controller using a TTL signal. Perfect. Even though it does not shut down completely (there is still ~1.25V on the output), it does the job.

Sensing part

Because Atmega328 can measure up to 5V max, I had to scale down the voltages of the cells. To do that I used voltage dividers. There are 5 of them, connected to ports A0..A4. Resistors (with values specified) are R1..R10 in the schematic.

Schematic & PCB layout

*Click on the images for hi-res version.

There is a 10K pull-up resistor (not shown in schematic) connected from BC337 base to Vcc to ensure that Voltage regulator stays off while uC is starting up.


This code was written using Arduino IDE (

int analogValues [5];
int voltages[6];

unsigned char i; // Loop variable
byte LEDs = 0;
byte tempLEDs = 0;
boolean turnOn = true;
boolean updated = false;
boolean firstrun = true;
byte portVal;

byte LEDstates[] = {
0xFF, 0xDF, 0x9F, 0x1F, 0x0F, 0x07, 0x03, 0x01, 0x00};

void setup()
// Set Transistor's pin to output
pinMode(8, OUTPUT);
digitalWrite(8, HIGH);

// Set LED pins to outputs
pinMode(5, OUTPUT);
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
pinMode(9, OUTPUT);
pinMode(10, OUTPUT);
pinMode(11, OUTPUT);
pinMode(12, OUTPUT);
pinMode(13, OUTPUT);

// Set analog inputs
pinMode(A0, INPUT);
pinMode(A1, INPUT);
pinMode(A2, INPUT);
pinMode(A3, INPUT);
pinMode(A4, INPUT);

// Disable Pull-up resistors on analog pins
digitalWrite(A0, LOW);
digitalWrite(A1, LOW);
digitalWrite(A2, LOW);
digitalWrite(A3, LOW);
digitalWrite(A4, LOW);

for (i = 0; i < 9; i++)
tempLEDs = LEDstates[i];

void updateLEDs()
PORTD = (PORTD & 0x1F) | (tempLEDs & 0xE0);
PORTB = (PORTB & 0xC1) | ((tempLEDs & 0x1F) << 1);

// Scale because of voltage divider by 2.624
void loop()
if (turnOn && updated)
digitalWrite(8, LOW);
updated = false;
if (!turnOn && updated)
// Serial.println("turn OFF");
digitalWrite(8, HIGH);
updated = false;

// Read status of all batteries
for (i = 0; i < 5; i++)
analogValues[i] = analogRead(i);

voltages[0] = analogValues[4];
voltages[1] = analogValues[3] - voltages[0];
voltages[2] = analogValues[2] - voltages[1] - voltages[0];
voltages[3] = analogValues[1];
voltages[4] = analogValues[0] - voltages[3];
voltages[5] = analogValues[2] - voltages[4] - voltages [3];

// Take care of low voltage per cell situations
//  Minimum threshold for a cell is 3.0V.
// Minimum value is 3/(5/1024) = 614.4
// Scaled because of voltage divider by 2.624,
//   so 3V = 614/2.624 = 234 units
boolean stopLoop = false;
i = 0;
while ( i < 6 && !stopLoop)
if (voltages[i] < 234)
stopLoop = true;
turnOn = false;
updated = true;
digitalWrite(8, LOW);
// Enter infinite
loop while (1) { };
//Serial.println(analogValues[2], DEC);
// Take care of LED's
if (analogValues[2] > 920) // 11.8V
tempLEDs = LEDstates[0];
if (analogValues[2] > 889) // 11.4V
tempLEDs = LEDstates[1];
if (analogValues[2] > 858) // 11.0V
tempLEDs = LEDstates[2];
if (analogValues[2] > 827) // 10.6V
tempLEDs = LEDstates[3];
if (analogValues[2] > 796) // 10.2V
tempLEDs = LEDstates[4];
if (analogValues[2] > 765) // 9.8V
tempLEDs = LEDstates[5];
if (analogValues[2] > 734) // 9.4V
tempLEDs = LEDstates[6];
tempLEDs = LEDstates[7];

// Something changed in total battery voltage
if (LEDs != tempLEDs)
LEDs = tempLEDs;

/* My old idea...

// First three LED's
tempLEDs = tempLEDs >> 5; // Right shift by 5 to get first three bits
tempLEDs = tempLEDs << 5;

portVal = PORTD;
portVal = portVal << 3; // Right shift to get rid of last three bits; portVal = portVal >> 3; // Left shift to restore first 5 bits to their positions
PORTD = portVal | tempLEDs;

// Restore temp value that changed because of all the shifting
tempLEDs = LEDs;

// Last five LED's
portVal = PORTB;
tempLEDs = tempLEDs << 3; // get rid of first three bits tempLEDs = tempLEDs >> 2; // position temp byte correctly

if (turnOn) tempLEDs = tempLEDs | 1;
PORTB = tempLEDs;

// Restore temp value that changed because of all the shifting
tempLEDs = LEDs;


if (firstrun)
updated = true;
turnOn = true;

// Delay before next run


Eagle files

Will be uploaded later

Music Box Thingy: a rotary sequencer v1.0


This post is about a fourth semester project that our group did. The project was featured in Roskilde 2010 Festival. I was responsible for electronics part of the product.

Everything started form an idea…

Decision was made to create something that would make it easier for people to “break the ice”. There were several iterations of the product till Music Box was born. We decided on creating a rotary sequencer. There were two versions that were used for real-world testing.

Implementation… v1.0

First test was done in a club called Culture Box.  This is where the first iteration of the Music Box v1.0 was used. It has a really simple design. Activation of the steps is done by some push-buttons with levers. Levers move and push a button when a can is inserted into a hole.

There are 32 holes in total (four instruments with 8 steps in each). This means that input from 32 buttons had to be gathered. We decided on using multiplexers this way expanding possible input count on Arduino.

There were four of these boards because each has 8 inputs that are sent through 1 channel (in normal words it is 8:1 mux).

For indicating which step the sequencer was on we used LED’s that went from the inside of the circle to the outer most hole.

LED’s are controlled by Arduino via serial-in-parallel-out shift register.


Now some photos from the Culture Box…

And this is me deeply thinking about how well it works ūüôā


Do not forget to watch in High Quality...

Exam presentation video

Stress testing Music Box

Inserting LED’s

Pitch for RedBull

More photos can be found on my facebook page:

To be continued…

This is first part of the Music Box description. Second part (Roskilde Version) is coming soon.

Arduino Uno has arrived!

This morning was quite awesome… Just before leaving home for university I noticed a post-truck driving by. It stopped near the entrance of my apartment. My heart started pounding… Maybe, there is my package. Yes, it was from Let Elektronik – Arduino UNO has arrived!

Here are some photos of it:

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Can’t wait till lectures are over. Time to do some coding ūüôā