Multirotors and Atmega

It came as a surprise to me that atmel processors are used in rc multicopters. There are purpose built boards for this kind of a hobby. There are mainly 3 different trees evolved in this scene

1st ardupilot (APM) a mega2560 based board, basically a arduino mega with barometric, acceleration and gyro sensors built in, as of 2.7 version boards lacking a magnetometer which is put in a GPS add on. Its regarded as a goto board for GPS functionality. It has a separate windows GUI mission planner. Board has special connectors builtin for connecting gps , power sensors speed sensors and almost everything else you can imagine to add to your flying apparatus. Its very easy to upgrade just go online in GUI and press a button. Downside is that its relatively expensive, bulky and fine tuning is a bit cumbersome. As of now it has evolved from 8bit Atmega controllers to 32bit St chipset, board is codenamed PixHawk or PIX for short.

2nd Multiwii. Basically its like a proprietary mega or 328 board. Everything applies except updating from mission planner. But for the price its a lot better. Coming from an arduino background you should go this route. You don't need to buy a multiwii board. A regular arduino will do. Go to eBay and acquire some sensors, Velcro tape or a glue gun and you're set. Code is open and developed on a daily basis. Also its much easier to add your own code to it. Code is all commented and easy to understand and modify.

3rd are proprietary 3rd party flight controllers for example-32bit CC3d, KK board series (latest 2,1), built-in types, where the board is a part of the frame. They arent that common but they have quite a following most of the time, for example there are some enthusiast who will bash whatever choice of FC(flightcontroller) you have as long as it isn't a KK board.

All of the ESC(Electronic speed controller)-s that i have come across have been controlled by Atmega8 series processors. They are used to make DC voltage into AC that controls the brushless motors on the multirotor. Atmega is used for getting the information from the FC and after that to control the RPM of the motor that it's connected to. All of the main calculations as to hoq fast every motor has to is done by the FC. ESC is just a dumb device that gets a signal and makes the propellers go zoom.

Today I disected a Ublox 6M Gps receiver, and it too had an Atmega chip as a supplementary communications platform.

Arduino 4x20 LCD and 2 inputs comparator

Staring a new build. So as to that I had an idea, that it can be helpful for everyone starting with code writing to try and manipulate this snippet. It's a simple code to operate a LCD and 2 inputs on A0 and A1. It compares the two with if and else. After the comparator it makes a readable output on the LCD. From here it's very simple to put the comparison into outputs of your own choosing.

//4x20 LCD, 2 sensors in A0 and A1 compare them and output to the LCD
// include the library code:
#include <LiquidCrystal.h>

// initialize the library liquidcrystal.h with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

int sensorPin1 = A0; // defines input pin
int sensorValue1 = 0; // make a varianle sensorValue
int sensorPin2 = A1;
int sensorValue2 = 0;

void setup() {
  // set up the LCD's number of columns and rows: 
  lcd.begin(20, 4);

}

void loop() {

  sensorValue1 = analogRead(sensorPin1); // get the value of sensor 1
  sensorValue2 = analogRead(sensorPin2); // get valur for sensor 2

    lcd.setCursor(0, 0); // Set cursor to top left
  lcd.print(sensorValue1);

  lcd.setCursor(0, 1);
  lcd.print(sensorValue2);

  if (sensorValue1 < sensorValue2){
    lcd.setCursor(0, 2);
    lcd.print("1 is higher than 2");
  }
  else{
    lcd.setCursor(0, 3);
    lcd.print("2 is higher than 1");
  }

  delay(200);
  lcd.clear();


}

Max7219 and a LED matrix with Arduino, blinking LED-s the hard way

DIY led matrix

DIY 7805 PSU

 First trial to make the 7219 work with Arduino. I had ordered the MAX7219-s a good few months ago, but still hadn't made anything with them. So this is mi stab at making them work. In mi junk bin i had a bunch of perf board and white led-s so just a matter of soldering together I thought. Well soldering is the easy part but to mi surprise it took a good hour or so to solder the 7805 coupled with 7219 and the led matrix together.

So mi first attempt. To replicate or try it for yourself you need.

• Soldering iron
• 30 LED-s
• MAX7219 IC
• 7805 Voltage regulator
• 10 uF and 100 uF capacitors
• jumper wires

Max7219 connected with DIY 5x6 Led matrix

Wireless 433mHz with Arduino, hitting the radiowaves

433mHz sender unit(left) and receiver unit (right)

I picked a pair of these up for 0.99$ each, so who can resist the tempation.

ACS712 30A interface with Arduino, measuring power usage

ACS712 30A sensor

The ACS712 is a hall-effect sensor, so when in using it be careful not to have any magnetic interference hitting the thing.There many variations of the IC this here is the 30A version. The current capabilities it can handle id conveniently located on the chip itself.

LCD and Arduino, getting readable output

16x2 on the top and 20x4 LCD on the bottom

The 16x2 LCD is salvaged from a 48V PSU that had lost it's magic smoke in a spectacular way. So guud guy that i was i hauled it home and dismantled it before it met it's end in a bin.

ENC28J60 and Arduino, ethernet for your microcontroller

ENC28J60

DATASHEET for the main chip on board.