FINAL YEAR PROJECT

MICROCONTROLLER BASED USER-FRIENDLY UPS

USMAN INSTITUTE OF TECHNOLOGYHAMDARD UNIVERSITY

GROUP MEMBERS

TAIMOOR ZAFAR (05B-004-IE)

UMAIR AHMED (05B-026-IE)

M.WAQAS JAWED (05B-022-IE)

FAHAD JUMA (05B-028-IE)

TABLE OF CONTENT

CONTENT1. INTRODUCTION2. COMPARISON TABLE3. THE STANDBY UPS4. PROBLEMS REGARDING THE LOCAL

MANUFACTURING OF UPS5. PROPOSED SOLUTIONS6. MAIN CIRCUITRY7. THE TRANSFORMER8. BATTERY CHARGING AND FULL BRIDGE INVERTER9. DISPLAY AND MONITORING CARD10. OSCILLATOR

PAGE NUMBER

• 4• 5• 6• 7• 8• 9• 10• 12• 14• 17

INTRODUCTION• UPS

Uninterruptible power supply (UPS) is an electronic device that continues to supply electric power to the load for a certain period of time during a loss of utility power or when the line voltage varies outside normal limits.

• UPS TYPES

A variety of design approaches are used to implement UPS systems, each with distinct performance Characteristics. The most common design approaches are as follows:

• Standby• Line Interactive• Standby-Ferro• Double Conversion On-Line• Delta Conversion On-Line

Practicalpower

Range (KVA)

Voltage Conditioning

Cost per VA Efficiency Inverter always operating

Stand by 0.5 Low Low Very High No

Line Interactive 0.5-5 DesignDependent

Medium Very High Design Dependent

Standby Ferro 3-15 High High Low-Medium No

Double Conversion On-Line

5-5000 High Medium Low-Medium Yes

Delta Conversion On-Line

5-5000 High Medium High Yes

COMPARISON TABLE

THE STANDBY UPS

The Standby UPS is the most common type used. In the block diagram illustrated below, the transfer switch is set to choose the filtered AC input as the primary power source (solid line path), and switches to the battery / inverter as the backup source should the primary source fail. When that happens, the transfer switch must operate to switch the load over to the battery / inverter backup power source (dashed path). The inverter only starts when the power fails, hence the name "Standby." High efficiency, small size, and low cost are the main benefits of this design. With proper filter and surge circuitry, these systems can also provide adequate noise filtration and surge suppression.

PROBLEMS REGARDING THE LOCAL MANUFACTURING OF UPS

Nowadays UPS are an essential part of our life. People usually buy UPS from the local market because they can’t afford the branded UPS like APC etc. Only the Systek and one or more companies are there which are producing efficient UPS but there User-friendly UPS or we can say there product with LCD display and monitoring are still quite expensive.UPS other than that of Systek are very less efficient. They usually failed to deliver the amount of power which is stored. About 40% of the energy is lost because of several different factors. The main factor which contributes heavily in the losses is a less efficient Transformer. So, we have tried to built these specialties which includes user-friendliness, cost-effectiveness as well as the improved efficiency.

PROPOSED SOLUTIONS• The solutions we proposed were as follows:1. In order to add user-friendly characteristic, we have added an LCD display

which are used to display user-friendly messaging.2. For improving the efficiency of transformer, we have designed and developed

an EI core transformer with silicon steel material. The results are amazingly appreciable.

3. Another characteristic which we have developed is the monitoring of the circuit.

4. This UPS is not only cheaper in its unit price but it is also very cost-effective in the manor that it is delivering the maximum amount of power stored in the battery . So you will have that amount of energy that much you have paid your electricity bill.

5. Another cost-effective feature in this UPS is that it have a deep discharge and overcharge protection for the battery. This will increase the life of your battery.

MAIN CIRCUITRY

THE TRANSFORMERThe topology which we have used to built the transformer is EI. Because it is the most cost-effective and easy to built core topology. We have developed three different Transformers on different stages. The first Transformer was a 70 Watt transformer. The second one was of 280 Watt. Which we showed in our last presentation. They both were of Iron core. The last one is of 380 Watt and its material is silicon steel.

Power calculation are as under:

Core Cross-sectional Area:

1.625inch X 2inch= 3.3

power in wattage:

(3.3 X 5.6)X(3.3 X 5.6)= 341.5104 watt

• Wire selection for primary side:

341.5104/300V = 1.138A

So 22SWG wire is suitable for primary

No. of turns for 300V:

9/3.3 = 2.72 turns par volt

300*2.72 = 818 turns

No. of turns for 220V:

220*2.72 = 598 turns

• Wire selection for secondary side:

341.5104/32 = 10.6722A

So 15 SWG is suitable for secondary side

No. of turns for 16V:

16*2.72 = 43 turns

BATTERY CHARGING AND FULL BRIDGE INVERTER

• THE BATTERY CHARGING CIRCUIT:

The battery positive terminal, which is connected to the connected to the center tape of the secondary winding. The battery start charging when the light is available and the primary 220V of the transformer is connected to the AC supply through the over charge relay. The 15A diode is connected in parallel of the npn transistors, the battery starts charging when the current is sink by the battery through the diodes.

• THE INVERTER BRIDGE:

The inverter bridge has 5 npn transistors in each branch, the collectors of the npn transistors is made common for each branch and then it is connected to the two ends of the secondary winding of the transformer. The oscillation of the inverter bridge depends on the output signal of the oscillator.

• THE RELAY LOGIC CARD

There are three relays in the relay card. One is DDR (deep discharge relay), second is Main relay and third is OVR (over charge relay). The DDR relay connects the output of the transformer 300V to the load. When the controller detects the low battery voltage it cut off the load from the output of the transformer through the DDR relay. The MAIN RELAY is used to connect the load with the UPS output in the absence of the AC power and connects the load to the main AC supply when main AC power is available. The OVR relay connects the main ac supply to the 220V input of the transformer. When the battery is fully charged the OVR relay disconnect the 220V input of the transformer.

DISPLAY AND MONITORING CARD

• THE MICROCONTROLLER:

The microcontroller is the main part of the display and monitoring card. The first job of the microcontroller is to observe its inputs and take the data from ADC and after processing it generates the output to the LCD, the data bus of LCD is connected to the PORT 0 of the microcontroller. The port 0 is open collector so we connect the port 0 With the 4.7 Kohm resistor array. The data bus of ADC is also connected to thee port 0 of microcontroller. The microcontroller will take the data from ADC and after some processing it will give the data to the LCD in order to display the battery voltages on the LCD. Similarly the controller is also monitors the output of 4047 oscillator, if there is an error in the oscillator output the controller cutoff the input of the inverter section and that instant the controller generates oscillatory signal for the inverter section through opto-isolator, at that time the UPS will run in the stand by mode.

• LCD:

We have used the 16X2 character LCD. The purpose of using the LCD is to display the massages, which tells the user about the progress of the UPS. The LCD displays the massage when the controller generates the enable signal to the LCD. The control pins of the LCD RS (register selection), R/W and E are connected to the P 2.5, P2.6, and P2.7 of the controller.

• THE ADC0808:

We have used 8 channel 8-bit ADC. The data bus of ADC is connected to the port 0 of microcontroller. Similarly the control pins of ADC such as START, EOC, and OE are connected to the P3.5, P3.6, P3.7 of the controller. The channel 1 of the ADC is connected to the battery voltages through resistor divider network, in order to attenuate the battery voltage, which is compatible with the input of the ADC. Through this we can give the protection to the battery. In future if we want to monitor the temperature of transformer, Inverter Bridge because we have remaining 7 channel of the ADC, which is handy for future enhancement.

• THE 74LS139:

This the divide by ‘n’ counter which is used to provide the 1MHz clock frequency to ADC. We use this as a divide by 2 counter. Because the ALE of the micro controller generates the 2MHz frequency, which is divided by 2 through the counter and then given to the ADC.

OSCILLATOR• OSCILLATOR

The 4047 oscillator generates 50 Hz clock cycle at pin no. 10 and 11. The clock frequency depends on the external resistor and capacitor. The output of the oscillator is connected at the inputs of AND gate.

• AND GATE:

The 2 input AND gate logic is used to cut off the frequency of oscillation of the inverter bridge as the result of power failure. The one end of both AND Gate is made common and connected to the P1.4 of the controller to enable the output for the inverter bridge.

• THE OPTO ISOLATOR:

The opto isolator is used to run the inverter in the standby mode. When the 4047 oscillator fails the controller disable the common input of the AND gate and generates the output for the opto isolator, which operates the inverter bridge in the stand by mode.

We would like to thank Engr. Salman Jaffery for his help, guidance and encouragement and Engr. Sajid Hussain for cooperating with us as an external and the people who are here to support and encourage us.

THANK YOU