Arduino_UPS

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An UPS made of old UPS and Arduino

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# Arduino UPS
An UPS (Uninterruptible Power Supply) made of my old (broken) UPS and Arduino.

# Documentation
The documentation consists of hardware and software part.  
The hardware documentation consists of used parts and electrical schemes. It resides in "hw_doc" directory.  
The software documentation consists of action diagrams.  It resides in "sw_doc" directory.  
Source code is included as well and can be found in "arduino_ups" directory.  
Every aspect of this project is thoroughly explained in this documentation.

# Hardware documentation
## Parts
* Old UPS (or a box to put everything in)
* 12V 7Ah battery - `CJ12-7` accumulator has dimensions to fit exactly in the battery compartment
* 12V power brick
* Arduino Uno
* LCD Keypad Shield
* Breadboard (using a smaller one)
* Wires
* Transistor (N MOSFET)
* Resistors: 20k, 10k, 2.2k
* Buzzer
* Power panel connectors
* Polymer fuses: one >=13V >=7A (main power), one >=13V >=1A (buzzer fuse :) )

## Tools
* Drill
* Screwdriver

## Schemes
### Physical scheme

![Physical scheme](https://raw.githubusercontent.com/kyberdrb/Arduino_UPS/master/hw_doc/Arduino_UPS_bb.png)

#### Power circuit
The power from the power brick goes into "Input 12V DC" jack. Then it leads to the polymer fuse. From there it
goes to the bread board and Arduino Uno power jack. The LCD Keypad Shield is directly connected to the Arduino
board. The LCD Keypad Shield is used for user interaction.

#### Voltage measuring
For voltage measuring I used voltage divider, which uses Ohm's law. R1 resistor is 20k, R2 is 10k

The calculation and the picture of the scheme for voltage measuring is shown below.

##### Calculation
We need to calculate, what the maximum input voltage from the power source can be, before the Arduino blows on fire :)
The closer it is to the nominal voltage of the power brick (in this case 12V), the more accurate voltage readings we will get,
but the less headroom we will have, when the voltage starts fluctuating (which is rather unlikly but possible).

Vout = ouput voltage (to the Arduino input pin)
Vin = input voltage (from the power source)
R1, R2 = resistance values of R1 and R2

Vout can be at most 5V beacuse we can provide to the Arduino input pins AT MOST 5V! Otherwise we will fry the Arduino.

Equations...

Vout = (Vin * R2) / (R1 + R2)  
Vout * (R1 + R2) = Vin * R2  
(Vout * (R1 + R2)) / R2 = Vin

Now we can replace the variables with the values.  
Vout = 5V  
R1 = 20k = 20000  
R2 = 10k = 10000

(Vout * (R1 + R2)) / R2 = Vin  
(5 * (20000 + 10000)) / 10000 = Vin  
Vin = 15V  => 15V can be the maximum input volate to the voltage divider from the power brick.

You don't have to do the math by hand. Instead, use [a calculator for voltage divider](http://www.ohmslawcalculator.com/voltage-divider-calculator) to do the job for you. You can customize there everything you need.

![Voltage divider scheme](https://github.com/kyberdrb/Arduino_UPS/raw/master/hw_doc/Voltage_divider_bb.png)

#### Buzzer
A N-channel MOSFET was needed to drive a buzzer (piezo speaker), which was rated for 12V. Pin #3 on Arduino was outputting PWM signal to the MOSFET's gate through the 2.2k resistor. The frequency of the PWM signal was transfered to the speaker, which then produced tone at that frequency.

![Buzzer scheme](https://raw.githubusercontent.com/kyberdrb/Arduino_UPS/master/hw_doc/Buzzer_bb.png)

The physical scheme ([Arduino_UPS.fzz](https://github.com/kyberdrb/Arduino_UPS/raw/master/hw_doc/Arduino_UPS.fzz), [Buzzer.fzz](https://github.com/kyberdrb/Arduino_UPS/raw/master/hw_doc/Buzzer.fzz) and [Voltage_divider.fzz](https://github.com/kyberdrb/Arduino_UPS/raw/master/hw_doc/Voltage_divider.fzz)) has been made with the help of **_Fritzing_**.

# Software documentation
## Voltage measuring

Using the computation mentioned in the hardware documentation, the maximum voltage that we can measure is 15 Volts. However the Arduino analog input pins can handle only 5 Volts which is why we put a voltage divider in between the battery and Arduino. The voltage that the voltage divider ouputs to the Arduino is less than 5V. In the program, the voltage is reversly transformed into the original voltage of the battery. The calculated voltage of the battery is then send to the LCD Keypad Shield to be outputted on the display.

## Buzzer

The buzzer provides an acoustic feedback about the voltage level of the battery. If it's too high or low (according to 
measuring and ATX2.2 standard), the buzzer starts beeping (different sounds for too low and too high levels). When everything 
is all right, the buzzer is silent. Below we can see the activity diagram (state chart) for the buzzer. The buzzer can exist in three (transition) states:

|&nbsp;&nbsp;&nbsp;&nbsp;State |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Description | Explanation
|---------|---------------------------------|-----------------------------------------------------------|
|&nbsp;State 1   | Not beeping -> Start beeping    | Starts beeping                                         
|&nbsp;State 2   | Started beeping -> Keep beeping | Continues beeping certain amount of time                                        
|&nbsp;State 3   | Enough beeping -> Stop beeping  | After the beeping time is over, the buzzer is silent for certain amount of time. Then the buzzer can start beeping again.

Table created with the help of [tablesgenerator.com](http://www.tablesgenerator.com/markdown_tables).

![Buzzer diagram](https://github.com/kyberdrb/Arduino_UPS/raw/master/sw_doc/Arduino_UPS_activity_diagram_buzzer.png)

This activity diagram produces one beep of certain length and then the buzzer becomes silent for a certain amount of time.

## User interaction
I was considering to split the user interaction on hardware and software part, but instead I decided to put everything about 
it here.

The user can interact with the UPS using the buttons. The function of each button is explained below. After pressing a button, 
a responsible action is taken which is defined in function "execBtnAction".

The DEBUG buttons are inactive! Their function is to test the voltage limits. When the voltage limits are crossed, the user 
gets feedback from the buzzer.

Button 1 - DEBUG - Voltage up  
Button 2 - Mute/Unmute the buzzer  
Button 3 - Brightness up  
Button 4 - Brightness down  
Button 5 - DEBUG - Voltage down  
Button 6 - Reset (can't be changed, it's hardwired to Arduino)

![Buttons diagram](https://github.com/kyberdrb/Arduino_UPS/raw/master/sw_doc/Arduino_UPS_buttons.png)

## Activity diagram

The program does exactly what is depicted in the activity diagram below. Most of the variables are declared and initialized 
in the "setup" function. The "loop" function takes care of the continuous program run. In addition to that, debugging 
printouts to serial 
console are distributed 
all over the 
code to 
monitor program's behavior on demand.

![Activity diagram](https://github.com/kyberdrb/Arduino_UPS/raw/master/sw_doc/Arduino_UPS_activity_diagram.png)

The activity diagram has been made with the use of [draw.io](https://www.draw.io/).

The entire code doesn't contain any "delay" function call, so that the program is very responsive, fast and stable. The 
avoidance of using the "delay" function allows to use buttons for user interaction, which would be otherwise problematic and 
cumbersome.

The source code is in the file 
[arduino_ups.ino](https://github.com/kyberdrb/Arduino_UPS/blob/master/arduino_ups/arduino_upc.ino) and can be found in 
directory "[arduino_upc](https://github.com/kyberdrb/Arduino_UPS/tree/master/arduino_ups)".

# Sources
How to Use a Buzzer (or Piezo Speaker) - Arduino Tutorial  
  http://www.instructables.com/id/How-to-use-a-Buzzer-Arduino-Tutorial/?ALLSTEPS

Piezzo Speaker - DBX12  
  http://www.db.com.hk/dbtronix/site/products_detail.php?pID=152

IRFZ 24N :: Power MOSFET N-channel TO-220AB 55 V 17 A  
  https://www.reichelt.de/Transistors-IRFU-IRFZ-/IRFZ-24N/3/index.html?ACTION=3&GROUPID=2894&ARTICLE=41737&OFFSET=16&SID=12VLelR38AAAIAABdkn9cb2bfeae5b6b044ddd7148786155b03ea&LANGUAGE=EN

IRFZ24NPBF - Documentation for the tranzistor (the closest i could find)  
  http://cdn-reichelt.de/documents/datenblatt/A100/IRFZ24N_IR.pdf

IRF740 - Documentation (supplemental documentation to the one mentioned above)  
  http://www.vishay.com/docs/91054/91054.pdf

Scheme - Controlling high voltage motor with tranzistor and Arduino  
  http://bildr.org/2011/03/high-power-control-with-arduino-and-tip120/
  http://bildr.org/blog/wp-content/uploads/2011/03/tip120-motor.png

Fritzing - The scheme-making tool  
  http://fritzing.org/learning/

Fritzing - LCD Keypad Shield  
  https://github.com/RafaGS/Fritzing/blob/master/LCD%20Keypad%20Shield.fzpz
  
Fritzing - tutorial  
  https://www.youtube.com/watch?v=M4CvUSkP9hw&t=3s
  
Arduino Uno pinout  
  https://micro-manager.org/wiki/Arduino
  
picoPSU-120 datasheet  
  http://www.mini-box.com/s.nl/it.A/id.417/.f  
  http://resources.mini-box.com/online/PWR-PICOPSU-120/PWR-PICOPSU-120-manual-engl.pdf
  
ATX v2.2 voltage tolerances  
  https://www.lifewire.com/power-supply-voltage-tolerances-2624583
  
Arduino - Blink without delay (huge efficiency improvement)  
  https://www.arduino.cc/en/Tutorial/BlinkWithoutDelay
  
const vs #define  
  http://forum.arduino.cc/index.php?topic=44023.0

LCD Keypad Shield demo code  
  https://www.dfrobot.com/wiki/index.php/Arduino_LCD_KeyPad_Shield_(SKU:_DFR0009)
  
LCD Keypad Shield - display brightness control  
  http://forum.arduino.cc/index.php?topic=97817.0
  
Tips and tricks for AVR controllers  
  http://www.nongnu.org/avr-libc/user-manual/FAQ.html
  
Variable types and modifiers explanation  
  https://stackoverflow.com/questions/3684760/where-are-the-local-global-static-auto-register-extern-const-volatile-var

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