This article was meant to come before
and somehow I've skipped it on my to do list. However, for everybody
wanting to add the microprocessor direct on to the controller without
the use of an Arduino board.
First we look at the option with a
stabilized 5 Volt power supply so we don't need to worry about
voltage regulators.
Let's put it on the breadboard first.
We start with placing the Atmega chip on the board and connect the
pins 7, 20 and 21 to the 5V bus and the pins 8 and 22 to ground. In
the same process we bridge the 5 V bus from the left with the 5 V bus
on the right of our breadboard and we do the same with the ground. I
also added a power socket where the 5 V power supply plugs into.
Next we add a 10K resistor from the 5V
bus to pin 1 of the Atmega to prevent it from resetting itself. A 16
MHz crystal goes between the Atmega pins 9 and 10 and 22 pF capacitor
connects to ground from each of the crystal pins. Finally we place a
reset button on top of the chip and connect one pin to the Atmega pin
1 and the other one to Ground.
You may add a LED at the digital pin 13
like on the original Arduino board but unless you want to carry on
and add a USB to Serial converter and test new chips without a
program on it there is no real need for it. However, I add the option
anyway. Just add a LED with a 330 ohm resistor to ground to the
Atmega pin 19 and you are done.
If you like to connect a stabilized 5
Volt power supply you can stop here. If you are planning to run the
unit of anything between 7.5 and 12 Volt you need to add a voltage
regulator. In this example I am using again the 1.5 A rated 7805
regulator. Please be advised, that the 7805 will not run the whole
unit with relays, LED's and PIR's. For further reference please
check my article “Adding a power supply”. The voltage regulator
connects with the output pin to the 5V bus, the middle pin to ground
and the input pin to any DC power supply giving between 7.5 and 12
Volt. Between the input pin and ground we connect a 100 uF
electrolytic capacitor and between the output pin and ground a 10 uF
electrolytic capacitor. Optional you can connect a LED with a 330 ohm
resistor between the 5V bus and ground as power indicator.
To connect everything to our room
management system we need to take of the input shift registers latch
pin from Arduino's input D2 and add it to the Atmega's chip pin 4,
the clock pin from Arduino's input D3 goes to Atmega pin 5 and the
data pin of the input shift register changes from Arduino input D4 to
Atmega pin 6. The next thing we change are the inputs from the output
shift registers. The latch pin moves from Arduino D5 to Atmega pin
11. The clock pin goes from Arduino D6 to Atmega pin 12 and the data
pin moves from Arduino D7 to Atmega pin 13. I have been already
working on some further development and since I am in need of using
D13 for a different purpose, the doors witch indicator LED had to
move to D8. That means we have to put the indicator LED connected to
Arduino D13 to Atmega pin 14. We also have to change the variable
declaration in our sketch. We look below the line where it says “All
the other Variables” and find the entry:
doorMonitor = 13;
and change it to
doorMonitor = 8;
The input of the photocell moves from
Arduino's A0 to Atmega pin 23. Finally we just have to connect the
ground to any common ground of the Atmega board and the 5V bus to the
output pin of voltage regulator. Now connect any DC power supply
between 7.5 and 12 Volt on common Ground and the input pin of the
voltage regulator and the unit is up and running without the Arduino
board.
If you go for the option with a
stabilized 5 Volt DC power supply just forget about the voltage
regulator and connect the 5V to the common ground and any 5V bus
since we have them all inter connected.
