can anyone help me...

[Darrel Taylor]

Hi Darrel,

Thanks lot,
Plz tell me, why u select FOSC32,whynot FOSC8.

I chose FOSC32 because I didn't know what crystal you were using.
If you had a 20mhz crystal FOSC8 would probably not work.
But even with a 4mhz crystal, FOSC32 will still work fine.

and my final ques is how to find the rising edge(tON) and Falling Edge(tOFF).I used the following code to find this,
This is a digital i/p,
go_vol1
btfss PORTB,0 ;checking whether porta pin is set or not
goto go_vol1 ;waiting
clrf TMR0
Duty_vol1
btfsc PORTB,0 ;keep monitoring rising edge
goto Duty_vol1
movf TMR0,0
movwf volt_val

Plz give me ur suggestion to use this code,If it is correct my work will get finish.

The code shown will wait for a rising edge, then measure the duration of the high pulse. if you add the same thing again for the low pulse, you'll have both values.

go_vol1
		btfss 	PORTB,0   ; Wait for rising edge 
		goto 	go_vol1
		clrf	TMR0      ; clear TMR0 for high pulse
Duty_vol1
		btfsc	PORTB,0	  ; keep monitoring high pulse
		goto	Duty_vol1
		movf	TMR0,0    ; put TMR0 value in W reg
		clrf    TMR0      ; clear TMR0 for low pulse
		movwf	tON       ; save timer value to variable

Duty_vol2
		btfss	PORTB,0	  ; keep monitoring low pulse
		goto	Duty_vol2
		movf	TMR0,0    ; put TMR0 value in W reg
		movwf	tOFF      ; save timer value to variable

> And also i m using LCD interface.wat should be the minimum delay b/w the commands to LCD.

It varies from display to display. I think the average is around 1.6ms, but some are as high as 2.5ms for commands. 2.0ms is standard with 50us DATA delay.

hth,

[kvrajasekar]

Thanks lot Darrel,I m very happy to see ur reply.

can i use the same codings for zerocrossing?bcoz zero crossing will occur every rising or falling edge.plz correct me if i am wrong?

[Darrel Taylor]

No I'm sorry, but you said the last one was your "Final Question".

Ok, 1 more.

If you're waiting for a zero-cross, then you probably don't need to time the event with TMR0.

Wait4ZeroCross                    ; Wait for zero-cross, up or down
    btfss   PORTB,0
    goto    WaitForHigh
WaitForLow
    btfsc   PORTB,0
    goto    WaitForLow
    goto    ZeroCrossDone
WaitForHigh
    btfss   PORTB,0
    goto    WaitForHigh
ZeroCrossDone

[kvrajasekar]

Thank you very much Mr.Darrel.

[sougata]

In a UPS (Offline I suppose) control your primary task would be to monitor mains for abnormality which includes under/over voltage, blackout/brownout. I suggest sampling the mains voltage at 0.5ms intervals. Also a premature zero-cross is a definite indication of mains failure. While I use PORTB.0 INT for the zero cross in asm you may use Instant Interrupt to make your life easier.

http://www.picbasic.co.uk/forum/showthread.php?t=3251

[kvrajasekar]

Hi sougata,

I m using power failure indication for UPS,wen it detects,i should start the inverter,also wen power resumption occur i should turn off the inverter and start with main.

How can acheive this task,plz give ur ideas to implement,I m using PIC16f72.

I am waiting for ur reply.

[sougata]

Hi,

It has happened in the past that I have committed to help on some specific issues offline of the forum but could not actually keep up to my commitments. So rather than showing you specific pointers it would be better if you cross each hurdle - one at a time. This would ensure that other forum members take interest try to solve your problems. Cause being a one man army I hardly get time to log onto the forum [I visit mostly when I am in trouble - I know sounds selfish ]

For your project :

While in mains -->
Monitor Zero Cross for abnormal timings
Monitor Mains Voltage (through Sense Transformer)

To achieve fastest transfer start sampling the mains voltage from the zero cross and validate against a lookup table to be within range every 0.5ms. Your ADC pin should see the mains voltage as a 100Hz fully rectified DC waveform. In a blind sampling can detect zero-crosses within 0.5mS accuracy. With a clock of 20MHz shouldn't be much trouble. Even works at 4MHz Internal Osc. I have done a square wave UPS with a 16F676 internal Osc (In full assembly However)

While in inverter mode --->

A periodic sampling (every 1 sec) of the input AC voltage may be enough alone. However if you require valid Frequency range then Zero-Cross might be needed. When found normal you can activate the restore to mains routine. Here you need to take care of output voltage regulation through PWM (software if square wave) and also protect MOSFETs from over-current, besides doing housekeeping such as battery-low, no-load shutdown, PC connectivity (16F73 recommended or any other with Hardware USART)

Breakup your job in discrete sections. Then assemble the whole when each one is ready.
Good Luck

P.S. - It is not that I do not want to share my code. But sometimes legally tied.