DSP 2010 based Compact Domestic Sinewave UPS /INVERTER

Isolated sensing of Mains Cycle-Cycle current Limiting Low cost driver LED/LCD display

Microcontroller based sinewave UPS/INVERTER with builtin charger

Introduction

This micro-controller based digital sine wave inverter using DSP (Digital Signal Processor) with full bridge configuration topology MOSFET switches with added features are as follows

Isolated sensing of Mains: This will ensure that even if Phase-Neutral connection is reversed at the input side there will not be any electric shock on the PCB or battery.

Cycle-Cycle current Limiting: This is a enhanced protection method for the short circuit / heavy load condition.

Low cost driver: The costly driver on the PCB

LED/LCD display: The PCB is designed with provision for LED, or LCD display.

This inverter is best suited for manufacturing for domestic applications as it is simple and easy. It consists only few components which are easily available, have only 3 smd components and with a single sided pcb. There are no windings which can possibly cause any error such as DC-CT or EE-16 transformers. Mounting of heatsink along with mosfets and soldering few components will complete this board. It consists of a LCD which will display all the parameters of the system and indicates any error during the functioning of the inverter. A low cost 16*1 Or 16*2 LCD will be of scrolling type, showing the status of the inverter such as battery voltage, mains voltage, inverter output voltage, inverter standby on/off, charger on/off, mains/ solar charging and many more. It is very simple to handle and very easy to set the values in the menu driven set-up mode.

This inverter is a very robust design which will not fail in any extreme conditions. 1. If 440V is applied to the AC input, it will not fail. It will indicate high voltage cut-off and restart when voltage is normal. 2. If AC mains is given to the inverter output, it will not fail. It will indicate phase input output reverse and continue to work after it is rectified.

3. It has fold-back current limiting for short circuit and heavy loads. At short circuit or heavy loads, current limiting action will take place instead of tripping which will lead to more reliability.

Features LCD display for indicating various status of the system like inverter voltage, mains voltage, battery

voltage, load, overload/short circuit status, battery low status, charger status etc.

LCD based Menu driven setup of various parameters like battery full charge voltage, battery low voltage, load condition, Inverter output voltage, charging current etc.

Protections against: Overload, short circuit, battery deep discharge, battery over charge, mains over voltage, reverse connection of phase in - phase out, reverse connection of phase and neutral of mains input. In all these error conditions will be shown in the LCD display.

Priority solar charging facility: When solar charger is connected mains charger will be in stand-by and priority will be for solar charger. Once battery attains full charge of set voltage changes over to ups mode (Care to taken while using this mode as sufficient solar panels are to be provided to the customer)

Delayed inverter cutoff for conditions like battery low, overload, short circuit etc. The system will automatically restart from cutoff after a few second buzzer beeps. The system will go to permenant cutoff if the error condition exists even after 4 restart.

1. LCD will display -

Battery voltage

Inverter output voltage

Percentage of load

Mains voltage

Changer on/off

Solar charging /mains charging

Inverter standby on/off

UPS mode / inverter mode

Phase input output reverse : whether mains is connected to inverter output

Neutral and phase reverse : whether neutral and phase is connected reverse

Overload : if load is above 100% and below 300%

Heavy : if load is above 300%

Short circuit

Overload trip

Heavy load trip

Short circuit trip

2. Menu driven set-up. There is no preset, the parameters such as battery low, charging current, inverter output voltage, load etc can be set by scrolling up and down keys and press enter.

3. Priority solar charging

4. Inverter/UPS selection switch, micro switch or ordinary switch selectable.

5. Inbuilt SMPS type constant current charging with full charge cut-off. 6. 20KHz operating frequency while inverter and charging, absolutely no sound.

7. Pure sine wave output

8. DSP based very low component cost design

9. Single sided pcb, easy to assemble without any smd components

10. Ideal for Mixed load application

Specification

Battery Input voltage : 12V DC - 48V DC Mains Input voltage : 230V AC, 50Hz.

Mains input range : 0V - 440V, 45Hz-65Hz AC Output (Inverter) : 230V +/- 3%, 50Hz

Inverter topology : Bridge type center aligned switching. MOSFET based. Inverter output power : 300VA - 3000VA

Battery charging : Constant current SMPS charging with full charge cutoff Charging current : Settable upto 15A

Charger working range : 120V - 270V AC Mains input

Highlights 1. Full bridge configuration based on power MOSFETs

2. DSP based intelligent control 3. LCD based display for user-friendly display of parameters and status

4. Protection against 440V mains input 5. Protection against reverse polarity

6. Dynamic short circuit protection with fold-back current limiting. 7. Protections against all possible errors like battery low, over load, heavy load, short circuit etc.

8. Early warning for battery low and overload conditions. System continue normally if the error is corrected.

9. Cutoff and auto restart with permanent cut after 5 consecutive cutoff.

10. SMPS type constant current charger with full charge cutoff.

11. Pure sinewave output resulting in silent operation of motor and fans. Safe to all kind of loads. 12. Ideal for Mixed load application

13. Indigenous design with proven technology.

14. Auto detect of LCD and LED. Can change between LED / LCD while the system is powered.

15. Protection against accidental output feedback disconnection.

Circuit Description

The circuit is given section by section as it is more convenient to explain.

The schematic above describes the ADC and other signaling section. The IC U7 is the DSP. Its pins 2 through 7 are the ADC pins. Pin 9 and 10 are the oscillator pins. The details are given in next page:

7

Pin Number Functional Description

1 Reset pin of microcontrollerΣ

2 ADC pin for AC input

3 ADC pin for AC output

4 ADC pin for load sensing

5 ADC pin for switch sensing

6 ADC pin for Temperature sensing

7 ADC pin for battery sensing

8 GND pin

9 Oscillator pin, Crystal connection goes to this pinΣ

10 Oscillator pin, Crystal connection goes to this pinΣ

11 Buzzer pin

12 Fan control. When this pin become +5V fan switch ON

13 Supply pin +5V

14 Solar Switch

15 Relay Drive

16 Fault Pin for short circuit protection.

17 Pin for LCD / LED control.

18 Pin for LCD / LED control.

19 GND pin

20 Supply pin +5V

21 Pin for LCD / LED control.

22 23

24 Drives the MOSFETs. Pin 23, 25 drive the GND side 25 mosfet and pins 24, 26 drives the upper side MOSFETs

26

27 GND pin

28 Supply pin +5V

Σ These pins are very sensitive. Do not touch these pins or extend wires from them, which can cause unwanted reset of DSPIC.

ADC section AC input and output sensing The AC input and AC output sensing is with the sense module. The resistors R44-R49 and R51-R56 determine the scale-down of the mains voltage. It is recommended to use metal film resistors for these parts. The module scale down the voltage and give to the dsPIC. It was found that it is better to put a filtering capacitor of 0.1uF disc from the mains sensing pin to GND. (From pin 2 to Pin 27). This give better stability for mains sensing. Whenever this capacitor is connected or removed the mains input is to be re-calibrated.

Load Sensing The load sensing is through the current transformer (CT) T1. You can use CT1200 or the equivalent. The shunt resistor R61 determine how much voltage is sensed for the load. A recommended value for this resistor is 100 Ohm divided by KVA. That is, for 1KVA R40 = 100 / 1 = 100 Ohms. For 500VA R40 = 100 / 0.5 = 200 = 220 Ohms or 180 Ohm.

Note: When mains is absent and inverter is switched off the voltage at pin 2, 3 and 4 will be very near to 2.5V. If the voltage is not as expected then the ‘No Load Set’ menu in the setup mode will not be completed.

Battery Sensing The battery sensing is through a simple resistor divider with R43, R69. The capacitor C31 is used for a filtering. The values of the resistors is not critical because the system has battery voltage calibration. But much drift in the values of the sensing resistors will result in improper sensing of the battery voltage. A usual mistake that found is that for 2 battery system the manufacturer put R43 = 47K which is the value of single battery. In this case when the battery reach near full charge the ADC input will reach its peak voltage and further increase in the battery voltage will not be sensed. The formula for R43 is:

R43 = 47 + 51 X (N-1) where N = number of batteries.

With this formula you get the resistor value in Kilo Ohms. It is expected that the voltage appear at pin 7 = ‘battery voltage / K’. For one battery K = 4.92. For example when battery voltage = 12V voltage at pin 5 = 12/4.92 = 2.44V. If number of battery = 2, the value K = 4.92 X 2 = 9.84. So when battery voltage = 24V the voltage at pin 5 is same 2.44V. If the battery voltage divider resistor values are changed the battery voltage sensing will be improper.

The usual error happen is the capacitor C31 across R69 has a leakage and hence the sensing voltage at pin 5 is much below the expected voltage. In this condition the battery voltage calibration can not be completed as expected. Other error that manufacturers make is the value of R43 is not increased when number of battery = 2 or more. This will make the voltage at pin 5 above 5V. In this condition the system will not sense the battery voltage if it rise above 25V (approximate) and hence the full charge will not be sensed.

Temperature sensing Temperature is sensed with an NTC or dedicated temperature sensing IC MPC9701. We recommend to use MCP9701 because non standard NTC cause improper working. The MCP9701 is placed near the heatsink with it flat surface facing the heatsink so that it can be tightned to the big heatsink. See the figure below

l

Sensing of Switches The switches are sensed through one ADC pin itself. This is for saving the controller pins. Resistances R57, R58, R59 and R70 form a divider network. The values of these resistances are selected in such a way that the voltage at pin 7 of the controller will be significantly different in different possible combination of the switches.

The 3 switches that can be connected to the connector CN4 are:

1. ON/OFF switch

2. Automotive battery / Tubular Battery selection switch 3. UPS / Inverter selection switch.

Also note that if needed we have provided seperate switch for Solar charger / Mains Charger selection . This switch is connected to the last pin of CN4. If the solar selection is not needed 4 pin connector can be used for CN4. If 4 pin connector is used the connection is exactly same as the old model dsPIC inverter.

Relay driving Pin 15 is for relay driving. This is done through Q26 transistor BC639. Also note that a torroid core T12.5 is used to suppress the conducted noise from the relay. This is described in the section ‘Winding of torroidal transformer’ in page 19 (or around). In order to speed up the changeover the relay switch on is done with a separate circuit. This is shown in the next page.

Buzzer Pin 11 through a transistor is for buzzer control. You can use a good quality B20 buzzer. It was practically found that low quality buzzers available in market which will fail without any reason after few weeks.

Fan control Pin 12 is for fan controlling. It is driven through a transistor. A regulator IC 7812 is used to assure that the voltage for fan does not go above 12V. This is recommended for reliable operation.

The fan should be screwed to the heatsinks, in such a way that air from the fan blow directly towards the heatsinks. The small heatsinks are aligned in such a way that a commonly available 3 inch fan can be screwed to the heatsink.

The fan is controlled as per the temperature sensed with the sensor connected to pin 6 of the controller. More details are given in section ‘Temperature sensing’ in the previous page.

LCD control The six pins 17, 18, 21 and 22 are used for LCD driving. These pins along with +5V, GND coming to the connector CN5 which is used to connect the LCD driving PCB. The wiring of LCD is given somewhere in the following pages of this document.

MOSFET driving signals and display handling Pins 23, 24, 25 and 26 are used to drive the MOSFETs. The schematic of mosfet driving section is given below

Schematic of MOSFET driving section. Relay fastening section also shown

The schematic of mosfet driving section is direct and self explaining. There is nothing more to explain with the MOSFET driving circuit. The relay fastening is done through the connector CN3, resistor R40, diode D17 and capacitor C26. A 45V winding from the transformer is to be connected to CN4. This winding can be done with very thing guage wire.

MOSFET driving and short circuit sensing The circuit shows one side drives of the MOSFETs. The upper and lower drives are shown. The upper and lower drives of the other side is exactly similar to this. The circuit also shows the current sensing and short circuit signaling section based on LM393 (U3)

MOSFET drive to the ground side MOSFETs is done with 4 transistors Q24, Q14, Q12 and Q22. Similar circuit is used to drive the other lower side MOSFETs. Higher side drive is with opto-coupler and its associated circuit.

Current sensing High speed sensing of MOSFET current is done with diodes D7, D8, D9, D10 and resistors R22, R23. Common point of D7 and D8 will have the voltage corresponding to the MOSFET current. This is compared by the opamp U3 (LM339) and the signal is given to pin 16 of the dsPIC. Note that this is only for the hazard current sensing of MOSFETs. The load measurement is done with current transformer CT1200.

View of the system from the user side As per the wiring given in the following pages the system has two terminals for battery connection, 3 terminals for AC input, AC output and Neutral. The LCD and switch wiring is to be connected as shown.

The 3 switches that can be connected to the connector CN4 are:

1. ON/OFF switch

2. Automotive / Tubular battery selection switch

3. UPS / Inverter selection switch. One more connection terminal is present in the CN4 which is used for solar charger selection. Note that solar charger / mains charger selection is not done manually, but automatically by the solar charger circuit.

Normally the ON/OFF switch is provided in the front panel. The UPS/Inverter selection switch is placed at the rear panel. Solar charger / Mains charger selection is not connected to a switch but is driven from the solar charger circuit. When the solar charger is active and charging the battery (there is sufficient sunlight to charger the battery) the solar charger will make the solar charger selection pin low. At this time the inverter will disable mains charger.

The Automotive battery / Tubular battery selection switch can be placed at the rear panel of the system.

The +ve connection of the battery taken from the big heatsink and the -ve wire taken from the PCB should have sufficient thickness to carry the battery current. When the battery is connected, the system will start with a special beep, like: beep-beep-beep-beep. This indicates the power on of the controller. This beep will be heard only when the battery is connected. After that this kind of beep will not be heard until the battery is disconnected and connected again.

If the above said power-on beep is heard during normal working of the system it means that the system got an unwanted reset. This can happen if the high current / high voltage wiring is taken near the low current signal wiring (LCD / switch wiring). This also result when the capacitors from pin 9 and 10 are not soldered. There is a chance to miss this capacitors since they are SMD parts fixed under the PCB. Also take care to fix the LCD without any electrical contact with the cabinet. It is wise to use not metal front panel and fix the LCD on it.

When the mains is in acceptable range the system will bypass mains and will charge the battery. The battery charging current will depend on the set value. When the battery voltage reach the full charge level the charging will be stopped automatically. When the battery voltage drops by ‘T’ volt the charging restarts. The magnitude of T depends on the type of battery selected (Automotive battery / Tubular battery selection). If tubular battery is selected T = 2.4V per battery. If automotive battery is selected T = 1.44V per battery. Also note that this depends on the correctness of the resistors R43, R69 connected to pin 7 of the microcontroller.

Fan controlling The fan is controlled as per the temperature sensed with the MCP9701. Temperature is sensed and fan controlling is done in mains as well as inverter mode. In case of excess temperature also the system will be inactive. The display will show the status. See the section temperature sensing at page 8 (or around).

The system will consider the mains voltage as OK when the mains is within a specified range. In inverter mode the acceptable range is from 100V to 285V and in UPS mode this is from 180V to 265V. When the mains voltage cross this range the system will activate the inverter if the standby mode is ON (front panel switch is ON). The software is giving a hysterisis gap for the changeover voltages. For example in UPS mode if the mains voltage is dropped below 180V the system will changeover to inverter but the system will return to mains if the mains voltage rises above 190V. That is, there is a gap of 10V. This is for the stability of the changeover. For low voltage changeover the hysterisis gap is 10V and in high voltage changeover the gap is 5V. This is because high voltage changeover will get a natural hysterisis.

In UPS mode the changeover to inverter will be fast and in synchronous with mains waveform. In inverter mode the changeover will be comparatively slow, but will be in synchronous with mains waveform.

Slow starting of the system is done if the mains is already absent and the standby mode is switched on in the absence of mains.

Fast changeover considerations The mains-inverter and inverter-mains changeover will be in synchronous with the mains waveform. For correct synchronous changeover the polarity of the transformer connection should be correct. This is automatically done by the system whenever the inverter is turned on. If the polarity is OK the inverter work normally. If the polarity is not correct the buzzer beeps continuously. If it happens, switch off the inverter and reverse the primary connection of the transformer.

In UPS mode the relay fastening voltage is very important for the fast changeover from mains - inverter. This is connected through 2 pin connector CN3. Without this support there is a risk of computer ree-boot and rare chance for mosfet failure.

Even when the front panel switch is off (standby off) the system will switch on the relay and will forcefully switch off the charger if the mains voltage is very high. This is for protecting the transformer and the MOSFETs from high voltages.

Inverter mode When the system is in standby mode the inverter will start if the mains is not in acceptable range. As stated above the smooth start will be done if the standby mode is switched on in the absence of mains. In inverter mode the system will be continuously checking the mains and if the mains is acceptable the system will try to synchronous the inverter waveform with mains. The inverter to mains changeover will happen only after the mains-inverter synchronization is correct.

If the load is within the overload limit, the output voltage will be maintained at the set value. Even if the output feedback is accidentally disconnected the system will not boost the output voltage, but instead will sense ‘no feed back’ error and will drop the output voltage.

In inverter mode the system will be continuously sensing overload and battery low voltage conditions. These levels are user settable in setup mode. When the error conditions exist the system will display the status and will give buzzer beep also. If the error condition continues for more time then the system will activate cutoff. The system will automatically restart from cutoff mode after a delay. In case of battery low cutoff there will be only one restart allowed. In case of overload cutoff system will give 5 restart chances.

After all restart chances system will activate permanent cutoff. System will come out of cutoff mode / permanent cutoff mode if the front panel switch is turned off or if the mains is restored.

Battery Low Sensing As described in ADC section above, battery voltage is sensed with a simple resistor divider. Proper values of these resistors are very important for correctly sense the battery voltage. Calibration of battery voltage display is essential for proper sensing.

Overload sensing The system sense the load through the current transformer CT1200. The value of shunt resistor across the CT determine the proper sensing of load as well as overload / short circuit condition. The load should be properly calibrated using calibrate menu in setup mode.

In setup mode there are 2 parameters that determine the overload sensing level. (1) load calibration under calibration menu and (2) Inv Load level in parameter menu. For example for a 500W system you can calibrate the load by connecting a 300W and making the display = 300. Then you can make the load limit parameter = 500.

When the system is set for 500W load limit the overload sensing will start from 12% above the level, that is 500+12% = 560W. The software is designed to limit the current through the CT at the rated current only. That is, if the load is set for 4A through the CT then the system will limit the output voltage so that the current through the CT will not exceed 4A. This means that when overloaded the output voltage will be dropped. But voltage dropping will not be done for the first 2 seconds of the overload.

When overloaded the output voltage is not limited for around 2 second. After that limiting starts. A heavy load or short circuit is detected by the dedicated circuit explained in page 10. The short circuit signal from the IC U3 will trigger a current limiting section in the dsPIC and will immediately limit the voltage. Compared to our earlier design the present method for short circuit sensing is different. Earlier the short circuit sensing was done with software. In case of heavy load or short circuit the output will be dropped to very low level and will be smooth started from there. Now the short circuit protection is done with hardware + software. In case of a heavy load the output is limited but it is immediately restored when the load is removed.

Cutoff mode The system enter cutoff mode in case of battery low, over load, short circuit or no feedback conditions. System will stay in cutoff mode for few second and will restart automatically. If the error condition still exist the system will enter cutoff mode again and will restart again. In case of cutoff due to battery low, system allow only one restart. Other cutoff will have 5 restart chances. If the system fail to work even after the last restart then permanent cutoff is done. When the system is in cutoff mode or permanent cutoff mode, quick restart will happen if the front panel switch is turned off or if the mains is applied.

Inverter-Mains changeover In inverter mode when the mains is restored the system will first try to synchronous the inverter waveform with mains waveform. The ac input sensing network and the capacitor between pin 2 and 27 are very important for the proper sensing and synchronization of the waveform. When the mains and inverter waveform are in phase the system will activate the changeover. The relay will be switched off and the display will show the changeover message. If battery low or overload condition was present at the time of changeover these conditions will be stopped and buzzer beep will be paused.

Connection diagram The connection diagram is given in the next page.

While connecting the LCD it is very important that the GND connection of the LCD SHOULD NOT come in contact with the cabinet through the fixing screws. If this happens the microcontroller will get unwanted resets and sometimes will hang, resulting in strange behaviors. These sometimes cause damage to the LCD. It is recommended to use plastic front panel instead of metal.

The connection to the LCD display can be done with thin wire. The connection of 0-250 winding of the transformer to the PCB and connection of AC terminals to the PCB is to be done with 40/36 guage (0.75 sq mm) wires. The connection of battery -ve, 7.5V winding of the transformer are to be done with 10mm2

wire.

The 40A relay used in the PCB is having high current terminals on the top side of the relay itself. It is recommended to take the Phase-In, Phase-Out connections from these high current terminals. For neutral connection a similar connection tag is provided on the PCB. Phase-in can be taken from the NC contact of the relay and Phase-Out can be taken from COM contact.

The connection diagram shown is the one used in the finished product. During setup mode exactly the same connection can be followed but connector CN4 for on/off switch connection will be used for setup switches. This will be explained later. There are 3 switches that select various modes of the system. These are: ON/OFF switch, automotive / tubular battery selection switch and UPS/Inverter selection switch. The switches are connected from CN4 connector. ON/OFF switch can be a microswitch or ordinary rocker type switch. The two other switches will be always ordinary rocker type switches. Whether to use microswitch or ordinary rocker type switch for ON/OFF switch can be programmed during setup mode.

The 3 switches used to browse through the menu during setup mode are connected to the same CN3 connector. During setup mode:

1. UPS/INV selection switch will function as Up switch.

2. ON/OFF switch will function as Down switch.

3. Automotive / tubular battery selection switch will function as Enter switch.

Also note that during setup mode all the three switches are microswitches. (press to ON, release to OFF type switch). There is no meaning to use rocker switch.

Complete Wiring Diagram

LCD PCB physical mounting The LCD driver PCB is mounted at the back side of the 16X1 (or 16X2 or 16X4) LCD in such a way that the components on the driver PCB is facing the rear side of the LCD PCB. See the photograph below. LED connection

The software is designed to automatically sense when the LED or LCD PCB is plugged while the system is powered. When the LED pcb is plugged it is sensed immediately and LEDs are driven accordingly. When LED PCB is unplugged and LCD is plugged the system will sense it immediately but it may take few seconds to display something. This is due to the LCD re-initialization delay.

The LED as well as LCD is connected from the same connector CN5. The diagram below shows the connection for LEDs. The ground pin (near to the relay) is considered as Pin 1.

During Setup-Mode the system will be permanently in LCD mode only, because LCD is essential in setup mode.

LCD display PCB component layout

.

Wiring with separate Control PCB and Power PCB

How to do Setup

To do the setup no special type connection is required. The setup switched are to be connected to connector CN4 to which normally the ON/OFF, Battery Type selection and UPS/INV selection switches will be connected. During setup there will be 3 switched: UP, DOWN and ENTER. The connections of these switches are as shown below.

There will be a default value already set for parameters such as battery low, battery full charge etc. So, there is no need to change these values. Only the calibration of the meter is required by entering the calibrate mode. Also after the wiring and finishing of the inverter in the cabinet, the no-load set should be done.

To enter setup simply press Enter switch and then power on the system.

The display will show ‘Enter Setup? N’. Note that the default choice is ‘No’ which prevents accidental entry to setup mode. To change the choice to Yes, press the Up or Down switch. Pressing Up swith again and again will toggle the choice between Yes and No. While the choice is Yes (display is showing: ‘Enter Setup? Y’) press Enter switch. Now the system is in setup mode. While the system is asking ‘Enter Setup?’ question, if the user do not press any key for around 15 seconds the system will come back to normal working without entering setup mode even if the selected choice is Y (yes).

When you enter setup (by pressing Enter switch while display is showing: ‘Enter Setup? Y’) the display will show the software version number for a while. Then the menu will be shown. Navigating through the menu driven setup is exactly same as our earlier microcontroller based sinewave designs. Details are given from the next page onwards.

Alternate way to enter setup This method of entering setup is introduced to make it possible to enter setup without disconnecting the battery. While the system is in normal working mode and inverter is switched off, press the following special key combination:

1. Enter 2. Up 3. Enter 4. Up 5. Enter 6. Down 7. Enter 8. Down

When this combination is pressed the system will produce a long beep. Before this beep ends keep Enter switch pressed. Then the display will show 'Enter Setup N'. You can enter setup as usual. If the key press sequence is correct you can hear a short beep on the 4th, 5th, 6th and 7th key press. On 8th

key press you will hear a long beep. Now release the down switch and keep pressing the Enter switch until the buzzer stop and display show

'Enter Setup N'

Now release enter switch and proceed as explained in the previous page.

While pressing the above special key combination, you should take care that the gap between two successive key press should not be more than 4 second. Also note that Enter Switch is functioning as battery selection switch also. When pressing the special key sequence the display will show messages like Automotive Battery / Tubular battery. But from the 5th switch onwards this message will be hidden. The 6th and 8th switches are Down switch which also function as inverter ON/OFF switch. But inverter ON/OFF will not happen if the key sequence is correct.

While pressing the above special key combination if any key is wrongly pressed, wait for around 5 or 6 second. Then start pressing the special key combination again from the beginning.

*

Menu driven setup We have provided a very user friendly menu driven setup procedure. The menu style is as below:

Main Menu

1. Calibrate Sub Menu 1

2. No Load Set Do NoLoad test 1.1 Bat V

3. Options 1.2 AC Out

4. Parameters Sub Menu 3 1.3 Inv Load

5. Discard 3.1 Microswitch 1.4 AC In

6. Done 1.5 Char Amp

3.2 LCD Lines 1.6 Exit

3.3 Exit Discard changes & Exit

Sub Menu 4

4.1 Bat Low

4.2 Bat Too Lo

4.3 Bat Full T

Save changes & Exit 4.4 Bat Full A

4.5 Inv Volt

4.6 Inv Load

4.7 Char Amp

4.8 Factory Set

4.9 Exit

When you enter setup you are starting at Menu1: Calibrate. If you press up switch you will see menu 2: No Load Set. Up switch is for going to the next item while Down switch is for going to the previous item. Menu is having auto-wrap facility, means: While displaying the last item in a menu if up switch is pressed then the first item is displayed. Similarly while displaying the first item in a menu if down switch is pressed then the last item is displayed.

To enter a menu just press the enter switch while the menu is displayed. For example if you want to enter the calibration menu: While you are in the main menu, press up or down switches until the display show 1. Calibrate and then press enter. From the sub menu if you want to go back to the main menu: press up or down switches until the display show ‘Exit’ and press Enter.

1. Calibrate Menu

The first menu if for calibrating various parameters that the microcontroller reads. For example the battery voltage is given to the microcontroller through a resistance divider network which scale down the voltage to 0.2034. Due to the variation of resistance value this scale down may not be correct. So the system may show slightly different reading. To make the reading correct we have to do the calibration. Calibration is required for Battery voltage, AC input volt, AC output volt, Inverter load and charging current.

2. No Load Set menu

This is for a kind of self test of the system. After doing the wiring you need to run the No-Load test at least once. This is required for correct functioning of the system.

3. Options Menu This menu is for setting various Options. At present two options are given : Microswitch/Rocker switch selection and Solar switch or Battery switch selection. This is explained below in detail.

4. Parameters menu

This menu is for setting various parameters like battery full charge voltage, battery low voltage etc. Normally these voltages will be automatically set by the microcontroller at power on time. Normally there is no need to change any parameters. 5. Discard Menu

Execute this menu if you have somehow done some unwanted changes in the setup values so do not want to write this to the non-volatile memory. The changes you have made will be discarded and the old values will be restored.

6. Done Menu

Execute this menu if you have done the necessary changes in the setup and want to write this to the nonvolatile memory.

Sub Menus Sub-Menus of Calibration Menu Calibration menu has five sub menus (plus one exit menu to go back to main menu). They are:

►1.1 Bat V, ►1.2 AC Out, ►1.3 Inv Load, ►1.4 AC In and ►1.5 Char Amp. The two numbers separated by dot in the display indicate the menu number and sub menu number. For example 1.3 Inv Load means Sub menu 3 of main menu 1.

The calibration menu is given for correcting the reading shown by the system. That is, if the battery voltage is 12.3V but the system shows 12.8V then we can use the calibration menu to correct the display. You have to use a good multimeter while doing the calibration. After assembling the PCB it is recommended to do the calibration because there is a good chance for slight variations in the display of various parameters due to the tolerance of resistors.

While doing the calibration of different parameters the display may seem not increasing / decreasing. For example when doing the battery calibration suppose the display shows 10V and you need to make it 12V. If you press UP switch the display may not increase as expected. But do not give up!. Just press and hold the switch. The display will change slowly. This is because the range of the calibration is too wide.

1.1 Bat V

This menu if for calibrating the battery voltage reading. To enter this menu press Enter while the display shows this menu. Inside this menu the display will show the present battery voltage. Suppose the display show 13.0V but with a good multimeter you measure the actual battery voltage as 12.5V. Now press Down switch to correct the reading. When the reading is OK press Enter switch.

1.2 AC Out

This menu if for calibrating the AC output reading. To enter this menu press Enter while the display shows this menu. The inverter will start with an output around 200V. During this working of inverter there will not be any AVR correction and output will vary as per battery voltage and load. It is expected to run this in no-load condition. Inside this menu the display will show the present inverter output voltage. Suppose the display show 180V but with a good multimeter you measure the actual inverter output voltage as 202V. Now press Up/Down switch to correct the reading. When the reading is OK press Enter switch.

1.3 Inv Load

This menu if for calibrating the inverter load reading. To enter this menu press Enter while the display shows this menu. The inverter will start and the output will be at the set inverter voltage. Inside this menu the display will show the present inverter load. You have to connect some considerable load to get good calibration. A load near the full load is recommended. Suppose you have connected 400W but the display show 380W. Now press Up/Down switch to correct the reading. When the reading is OK press Enter switch.

1.4 AC In This menu if for calibrating the AC input reading. To enter this menu press Enter while the display shows this menu. User should connect the mains while running this setup. To get good calibration, it is recommended to input an AC voltage above 200V. Inside this menu the display will show the present mains voltage. Suppose the display show 230V but with a good multimeter you measure the actual AC input voltage as 238V. Now press Up/Down switch to correct the reading. When the reading is OK press Enter switch.

1.5 Char Amp

This menu is for calibrating the charging current. To enter this menu press Enter while the display shows this menu. The charger mode will start. Note that you have to connect a good ammeter in series with the battery and input the mains supply. Charger will function irrespective of the battery voltage. There will not be any full charge cutoff. You have to connect an ammeter in series with the battery. The battery and ammeter connection should be very firm. Any battery side loose contact will cause excess voltage across the MOSFET since the charger is functioning without any full charge cutoff. This can cause MOSFET damage. Inside this menu the display will show the charging current you have set in the parameter menu. For example if you have set 8A in the parameter menu then the display will show Char Amp = 8A. The display will be steady and will not change. Initially the ammeter connected in series with the battery will show 0A. Press up key for a long time and the ammeter will start showing the current. Using UP and DN switches bring the current to the desired value. Press Enter when done. The mains should be disconnected only after pressing the Enter switch. 1.6 Exit

This menu is to exit the submenu and go back to the main menu Calibration.

Menu 2: No Load Set

Inside this menu the system takes some readings that are important for the correct working of the inverter. It is very important to run this menu at least once. During no load set the system also take some readings which are important for proper sensing of ac input, ac output and load feedback. For proper working of inverter and charger these parameters are important.

While doing no load set the mains should not be connected. If mains is present the system will not complete no load set. It is supposed that voltage at pin 2, 3 and 4 should be around 2.5V. If the voltage is not within +/- 2% the system will not complete no-load set.

Very Important: If you replace the transformer or change the primary or secondary connection of the transformer you should run the No Load Set at least once. This is important because inside this menu the system sense the polarity of the transformer. It is needed for correct line interactive changeover. Incorrect polarity can cause the re-boot of the computer and sometimes damage the MOSFETs.

Sub-Menus of Options Menu Options menu has only two sub menus (plus one exit menu to go back to main menu). They are:

►3.1 Microswitch ►3.2 Solar Switch ►3.3 LCD Lines

3.1 Microswitch

This menu is used to select whether the user needs microswitch or simple switch for inverter ON/OFF. To enter this menu press Enter while the display shows this menu. Inside this menu the display will show ‘Microswitch Y’ or ‘Microswitch N’. If Y is selected it means microswitch type ON/OFF switch. If N is selected it means ordinary ON/OFF switch. User can change between Y ◄► N with up or down switches. When the correct option is selected press enter switch

Tubular battery / Automotive battery selection

If user has selected switch 2 to function as Tubular battery / Automotive battery selection switch then Tubular battery will be selected if switch is closed. Automotive battery will be selected if switch is open. When tubular battery is selected Bat Full T voltage (selected in menu 4.3) will be considered as battery full charge voltage. Bat Full T-1.0V will be considered as battery reconnect voltage. When automotive battery is selected Bat Full A voltage (selected in menu 4.4) will be considered as battery full charge voltage. Bat Full A-0.6V will be considered as battery reconnect voltage.

Solar Charger Mains charger selection If user has selected switch 2 to function as Solar Charger / Mains charger selection switch then solar charging will be selected if switch is closed. Mains charging will be selected if switch is open. This is exactly as our old sinewave models. When the system is in solar charging mode, mains charger will be forcefully disabled irrespective of battery voltage. When mains charger is selected the charger will function as usual. The zero drop solar charger circuit we have provided can automatically switch to solar charging when sunlight is present.

Note: When switch 2 is selected as Solar Charger / Mains charger selection switch, the system will assume the battery as Tubular battery. So the Bat Full T voltage (selected in menu 4.3) will be considered as battery full charge voltage. Bat Full T-1.0V will be considered as battery reconnect voltage.

3.3 LCD Lines

This is a new menu item added from version 4.0 onwards. When entering this menu the display will show the number of lines in LCD. You can use 1 line, 2 line or 4 line LCD. With up/down switches the number of lines can be selected. There is no meaning to select more than 4 number of lines. If selection is more than 4 then the system will take lines = 4.

Sub-Menus of Parameter Menu

Paremeter menu has eight sub menus (plus one exit menu to go back to main menu). They are:

►4.1 Bat Low, ►4.2 Bat Too Lo, ►4.3 Bat Full T, ►4.4 Bat Full A, ►4.5 Inv Volt, ►4.6 Inv Load, ►4.7 Char Amp and ►4.8 Factory Set. The two numbers separated by dot in the display indicate the menu number and sub menu number. For example 4.3 Bat Full T means Sub menu 3 of main menu 4.

4.1 Bat Low

This menu is for setting the battery low voltage (that is, the battery voltage level at which the battery low warning should start). To change this simply press enter while this menu is displayed. The display will show the present setting. Press Up or Down switches to change to the desired value and press enter. The default value for this parameter is 10.0V. Normally you need not change this.

4.2 Bat Too Lo

This menu is for setting the battery low too voltage (that is, the battery voltage level at which the system go to immediate cut). To change this simply press enter while this menu is displayed. The display will show the present setting. Press Up or Down switches to change to the desired value and press enter. The default value for this parameter is 9.0V. Normally you need not change this.

4.3 Bat Full T

This menu is for setting the battery full charge voltage for Tubular battery (that is, the battery voltage level at which charger turns off). Note that we have an option to use switch 2 for battery selection (see option menu). To change this simply press enter while this menu is displayed. The display will show the present setting. Press Up or Down switches to change to the desired value and press enter. The default value for this parameter is 14.0V. Normally you need not change this.

For tubular battery, system automatically select the battery charge reconnect voltage as Bat Full Voltage - 1.0V

4.4 Bat Full A This menu is for setting the battery full charge voltage for Automotive battery (that is, the battery voltage level at which charger turns off). Note that we have an option to use switch 2 for battery selection (see option menu). To change this simply press enter while this menu is displayed. The display will show the present setting. Press Up or Down switches to change to the desired value and press enter. The default value for this parameter is 13.8V. Normally you need not change this. For Automotive battery, system automatically selects the battery charge reconnect voltage as Bat Full Voltage - 0.6V

4.5 Inv Volt

This menu is for setting the output voltage of inverter. To change this simply press enter while this menu is displayed. The display will show the present setting. Press Up or Down switches to change to the desired value and press enter. The default value for this parameter is 220V. Normally you need not change this.

4.6 Inv Load

This menu is for setting the inverter load. To change this simply press enter while this menu is displayed. The display will show the present load setting. Press Up or Down switches to change to the desired value and press enter. The default value for this parameter is 500W.

4.7 Char Amp This menu is for setting the charging current. To change this simply press enter while this menu is displayed. The display will show the present load setting. Press Up or Down switches to change to the desired value and press enter. The default value for this parameter is 8A.

4.8 Factory Set Pressing Enter in this menu will load the default factory settings for the parameters.

4.9 Exit

This menu is for exiting from the sub menu and go back to the main menu Parameters.

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Winding of torroidal transformer

(For noise suppression) Winding of T12.5 torroid (noise suppressor) To wind suppressor with 2 winding, take 2 wires of different colours and wind them together on a torroid core T12.5 or nearer size. Wind 5 or 6 turns. The number of turns is not critical. Connect to the PCB as shown below.

Changes in the PCB for various battery voltages For PCB (12MOSFET model) 12V Battery: 1. IC 7812 (U5) is not required. You have to 12 volts circuit

2. Battery sensing resistor R43 should be 47K 3. MOSFETs should be minimum 30V or more. The suitable part numbers are: 90NF03, IRL3713, 80NF55, 55NF06 etc. 90NF03 and IRL3713 can be used for 800VA. 80NF55 van be used for 750VA. 55NF06 can be used for 500VA. But if you use 90NF03 / IRL3713 for 500VA you will get better result.

4. The capacitors C4, C5, C6 and C7 connected across the battery should be 25V or more. Maximum micro farad available in the size can be used.

For PCB (12MOSFET model) 24V Battery: 1. IC 7812 (U5) is required. Use bigger heatsink because it is common for 7805 and 7812. Alternatively Falcon’s 3 terminal SMPS can be used for 7812 and 7805. There is no need of heatsink.

2. Battery sensing resistor R43 should be 100K 3. MOSFETs should be minimum 50V or more. The suitable part numbers are: 80NF55, 55NF06 etc. 80NF55 can be used for 1500VA. 55NF06 can be used for 1000VA. 4. The capacitors C4, C5, C6 and C7 connected across the battery should be 35V or more. Maximum micro farad available in the size can be used.

For PCB (24MOSFET model control) 36V Battery:

1. IC 7812 (U5) is not required. You have to connect 12 volts circuit 2. Battery sensing resistor R43 should be 150K

For PCB (24MOSFET model control) 48V Battery:

1. IC 7812 (U5) is not required. You have toconnect 12 volts circuit 2. Battery sensing resistor R43 should be 220K

For PCB (24MOSFET model) 36V Battery

1. All 24 MOSFETs should be minimum 75V or more. The suitable part numbers are: 80NF10. You can go up to 2000VA with this MOSFET.

2. Diodes D7, D8, D9 and D10 should be 1N4935, 1N4936 or BYV26E. 3. The capacitors C3, C5, C6, C7, C8 and C9 connected across the battery should be 50V or more. Maximum micro farad available in the size can be used .

For PCB (24MOSFET model) 48V Battery

1.1.1. All 24 MOSFETs should be minimum 100V or more. The suitable part numbers are: 80NF10. You can go up to 3000VA with this MOSFET.

1.1.2. Diodes D7, D8, D9 and D10 should be 1N4935, 1N4936 or BYV26E.

1.1.3. The capacitors C3, C5, C6, C7, C8 and C9 connected across the battery should be 100V or more. Maximum micro farad available in the size can be used

4 Stage Battery Charger

4 Stage Charger Stage1: This is constant current charger. This stage will be in effect until the battery voltage reach full charge level.

Stage2: When battery voltage reach the full charge level stage 2 starts. In this stage battery voltage is kept at the full charge level. Due to this the charging current will slowly come down. When the charging current comes below 1/4th of the set charging current the 3rd stage starts. If system continue in stage 2 for more than 5 hours then stage 3 is forcefully started.

Stage 3: It is nothing but charger off mode. As a result the battery voltage will start falling. When the voltage drops below the reconnect level stage 4 starts.

Stage 4: Stage 4 is float charging stage in which the controller give a very low charging current to keep the battery voltage at the re-connect level itself. System continue in this stage as long as the mains is present. From any stage the system will restart with stage 1 if mains fail and restore after some time.

1. In Setup Mode there is a new menu for selecting Charger type. You can select 4 Stage Charger or old 2 stage Charger. Under the Options menu a new item named ‘2-Stage?’. If you select ‘Y’ (Yes) for that then the charger will be 2-Stage. By default the charger will be 4-Stage.

2. In the Parameter menu there are two new items: Inv Start At and Inv Stop At. These are useful for automatically starting inverter when solar charger is present. When battery become full with solar charger it is desirable to switch to inverter mode even when mains is present. When inverter is running from battery and battery voltage is dropped to certain level the system should come back to mains mode. The working is as below:

a. Suppose the Inverter Start At level is 14V and Inverter Stop At level is 11V.

b. In solar charger mode (the Charger Active signal from external solar charger is present) when the battery reach 14V the system will forcefully start inverter even when mains voltage is good. Note that front panel ON/OFF switch should be in ON position.

c. The inverter will work until the ON/OFF switch is turned off or when the battery voltage drop to 11V. The normal activities like overload / short circuit sensing will be present in this mode also. d. If you do not need this feature just make the Inverter Start At level to a high level, say 18V.

Transformer details

Copper Wire

Transformer (500VA)

Item Specification

Core Type Type 16, Stack 2 ½ inch, CRGO. Split Bobbin

Voltage Turns Guage

Primary 7.5V 14T 11 SWG X 2

Secondary 0-250V 0-467T 22 SWG

*Split bobbin****

Split area 1

Split area 2

Relay boost 0-40 0-75T Very thin wire Split area 2

Transformer (750VA)

Item Specification

Core Type Type 43, Stack 2 ½ inch, CRGO. Split Bobbin

Voltage Turns Guage

Primary 7.5V 13T 12 SWG X 4

Secondary 0-250V 0-433T 19 SWG

*Split bobbin****

Split area 1

Split area 2

Relay boost 0-40 0-69T Very thin wire Split area 2

Split Bobbin is very important

Split bobbin is very important for the transformer. Non-split transformer will have slightly good regulation, but it will result more MOSFET current and thus produce more heat, in inverter as well as charger mode. For split bobbin the no load current from battery in inverter mode will be less than 1 AMP. But in case of non-split bobbin it is found to be more than 2.5A.

Transformer (500VA) Aluminium Wire

Item Specification

Core Type Type 43, Stack 2 inch, CRNO. *Split bobbin**** Voltage Turns Guage

Primary 7.5V 13T 9 SWG Split area 1

Secondary 0-250V 0-433T 19 SWG Split area 2

Relay boost 0-40 0-69T Very thin wire Split area 2

Vendor List

Item

MOSFETs and other electronic components

Cabinet

Heatsink

Transformer

PCB

LCD display

CT-1200

Item available from

PERFECT METAL WORKS #339/1-4, ANANTHA RAMAIAH WOOLLEN

FACTORY COMPOUND

OPP:SATELLITE BUS TERMINAL

MYSORE ROAD, BANGALORE -560 026 TELE : 080-26756936

TELE FAX : 080-26753163

EMAIL : sureshnahar@gmail.com

CONTACT PERSON: SURESH KUMAR NAHAR / MAHIPAL NAHAR

Nimishambha Electronics Bangalore

5A PCB Mountable.

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Clipping of waveform

For a single battery inverter (12V) we are recommending primary winding of 7.5V and secondary winding of 270V. By calculation we can find that even when the battery = 9V the system can maintain output sinewave shape at no-load. In loaded condition the system can maintain the sinewave shape at 10V or so.

But this is not needed for some cases. You may increase the primary winding (for example 8.5V instead of 7.5V). Then when the battery voltage drops, the system will start clipping the sinewave shape for maintaining the output. This clipping will not cause any noise in the system. The only thing is that the wave shape is detectable with an oscilloscope. But since the primary voltage is increased the current through the MOSFETs will be reduced. This is an advantage.