AVR Development board, Step-by-Step-Tutorial

How to build an Atmega8 development board


Adding an Electrolytic Capacitor

We will now add an Electrolytic capacitor to the board which is a two-lead capacitor that offers high level of capacitance per unit volume. Electrolytic capacitor is used to filter or reduce electrical noise and also power your circuit during short power drops from your battery (or any other power source). These capacitors have positive and negative polarity and hence take care to not connect the wrong leads.

Add Electrolytic Capacitor

Plug the capacitor exactly as shown. The negative lead of the capacitor is pushed to the right side of the board (the column with the rightmost headers) and the positive lead to the left of that (which is used as positive bus).

Generally positive lead of the capacitor will be slightly longer than the other. Another marking is that the side with a negative lead will have a black strip on the capacitor and marked (as shown in the image).

I have added a Philips 100µF (micro farad), 25 Volt capacitor. If you already have a capacitor with different voltage, use them. Just make sure that the capacitor rating is much larger (at least twice) than your batteries voltage.

Insert CapacitorAtmega8_dev_board_schematic_e_capacitor

Bend the capacitor leads to connect the headers as shown.

Bend and connect Capacitor leads schematic_eC_solder

Solder the last pin in the programmer header to positive line of the capacitor.

Solder Capacitor to Power lineschematic_prog_power

Add two more black wires, one ground line to pins PB1 and PB2 and the other for the programmer.

Add two black wiresground_pins_schematic

Observe how the wires are carefully bent. The ground of capacitor, the headers and the ground of programmer should be connected.

Bend the leadsconnect_eC_Pins

Solder the wires, header pins and capacitor lead as shown in the image.

Solder wires, headers and capacitor leads

Now solder the power line of capacitor to PORTB header

Solder Port B powerline portb_power_line

Below the capacitor we will add a voltage regulator. As the name says, voltage regulator regulates the input voltage so that the output can be used to maintain a constant voltage. Our microcontroller requires a constant 5V input and the reason we have used a three pin LM7805 voltage regulator.  

Add Voltage Regulatoratmega8_dev_board_regulator

Voltage regulator has three pins. With the pins down and the metal side towards you, the left side is the regulated 5V (Vout), center pin being ground (Gnd), and the rightmost is the input voltage (Vin) which goes to batteries positive side. Vin should be in the same column as the power line of your board and ground in the same column as ground line.

Bend the regulator leads as shown in the image. Vout should be bent towards the top side of the board and the other two pins backwards.

Bend and connect voltage regulator

Solder ground line of regulator to ground line of board, and Vout to power line of the board.

Solder regulator leadsatmega8_dev_board_regulator_conn

Add a two pin header in such a way that one pin is in line with Vin of regulator and the other in line with regulator’s ground pin.

Add battery pins

Solder the header pins and the regulator pins. This header is used to connect your battery that powers your circuit.

Solder battery pinsatmega8_dev_board_battery_conn

Connect two more wires to PIN-21 and PIN-22. Add a red wire to PIN-21 and power line (headers in the middle) and a black wire to PIN-22 and ground line (rightmost header). This connects the power line to microcontroller

Connect power and gnd to mc

Solder the entire line of pins and wires together as shown in the image

Solder all connections connect_power_to_mcu

Add two more wires to left side of the board. This connects the ground and power lines of bottom header and top header.

Power and gnd to left side

Solder the two wires to the header pins.

Solder gnd and power lines connect_power_to_left_side

Tutorial index:

  1. Introduction to AVR Board and Parts required
  2. Building the board- Part I
  3. Building the board- Part II
  4. Building the board- Part III
  5. Building the board- Part IV
  6. Adding LCD header (Optional)

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