Rewriting lfuse and hfuse of Atmel Atmega series

Atmel Atmega micro controller if set correctly will work fine. But when you tinker with its setting. Things get out of control. One such problem is when you set the wrong fuse setting of the device to use the external crystal oscillator.

  1. Connect the microcontroller with the USBASP programmer
  2. Open the command prompt 
  3. write the command
    avrdude -c usbasp -p m32 -t
  4. This will open a terminal where you will write
    read lfuse
  5. Note down the settings
  6. Then write 
    read hfuse
  7. Calculate the correct fuse setting and then write
    avrdude -c usbasp -p m32 -U lfuse:w:0xe1:m -U hfuse:w:0x99:m


These setting specified in the above post is incorrect. 
Calculate the fuse setting in advance
Also remember the JTAG pin will also be set correctly
Never Change SPI setting without reading document. Changing this setting will result in non-functioning of SPI and the programming can only be done with manufacturer programmer. 

The above said procedure is verfied on the follwing micrcontrollers:

  • ATMEGA16
  • ATMEGA32

Custom LED Display

From very long time I was thinking of making a custom LED Board. But i was reluctant to make it. Because of the calculation of current and voltage. It is a simple Ohm law follower with the addition of heat exchange equation taken into account. 

Temperature Controlled Relay

This circuit uses very basic components. The use of mm74c922 integrated circuit makes it different from other. This hardware based scanning makes the code really simple. 

The use of Atmega16 can be avoided but this allows for complex coding structure to be stored. Due to cost associated with the micro controller. 

External crystals are avoided as the device will be used for low frequency of up to 100 Hz. Which can be used easily be handled by the internal clock. The deviation of clock timing should be taken into account when programming.

Schematic of Temperature controlled relay

The LM35 series are precision integrated-circuit temperature devices with an output voltage linearly-proportional to the Centigrade temperature

Variable Voltage Power Supply

I was searching for a variable voltage power supply which can be used in multitude of situations. Ranging from testing to deployment in the final circuit design. It is not hard to find various IC, which does regulation. 

One such integrated circuit is LM317

LM317T Variable Voltage Power Supply
Lm317T PCB layout
Lm317T PCB bottom Copper