16F72 digital clock - Electronic Circuits Projects Diagrams Free

GreenBeret · 29th October 2009, 05:02 PM

Hi all,
i am new to PIC. I am trying to create a digital clock with 16F72 and Hitech C.
I want to use timer1 in sleep mode with backup battery when the external power goes down..

I want to get precise timing for half a second to toggle second LED to make it blink once in a second. ie. half of a second in OFF condition and half of a second in ON condition so that i can see a proper blinking of 60 times in a minute.

Please suggest a crystal speed that i can use for this requirement with its prescaler. I dont like to set the timer1 with a initial value because it will cause precision errors in time.. i would like to use bresenhams method for timer to get precise timing. Please suggest...

sahu · 29th October 2009, 06:16 PM

Quote:

Originally Posted by GreenBeret

Hi all,
i am new to PIC. I am trying to create a digital clock with 16F72 and Hitech C.
I want to use timer1 in sleep mode with backup battery when the external power goes down..

I want to get precise timing for half a second to toggle second LED to make it blink once in a second. ie. half of a second in OFF condition and half of a second in ON condition so that i can see a proper blinking of 60 times in a minute.

Please suggest a crystal speed that i can use for this requirement with its prescaler. I dont like to set the timer1 with a initial value because it will cause precision errors in time.. i would like to use bresenhams method for timer to get precise timing. Please suggest...

can u provied it ckt dia.?

GreenBeret · 29th October 2009, 06:47 PM

I dont have any circuit as of now... My idea is to connect PORTB to 7segment display parallely and scan segment using PORTA. I know we can use 32.768KHz crystal, but it will take 8seconds delay to overflow. I want to use this low speed crystal because of power saving... I wanted to 0.5 second notification for second blinking...

sahu · 29th October 2009, 06:54 PM

Quote:

Originally Posted by GreenBeret

I dont have any circuit as of now... My idea is to connect PORTB to 7segment display parallely and scan segment using PORTA. I know we can use 32.768KHz crystal, but it will take 8seconds delay to overflow. I want to use this low speed crystal because of power saving... I wanted to 0.5 second notification for second blinking...

i have F84 Miniature Real-Time Controller, but it is no usefull for u.

blueroomelectronics · 29th October 2009, 06:54 PM

With no prescaler it should take 2 seconds to overflow. You can bsf the top two bits on the timer register to cause overflow every 0.5sec
bsf will not reset the prescaler.

GreenBeret · 29th October 2009, 07:29 PM

Thanks blueroomelectronics for your help.
Here i have some more doubts according to your method...
1. While setting top two bits, will i loose some instruction cycles and will it lead to precision errors..?
2. After each overflow, do i need to set the top two bit again.. meaning for each overflow, do i need to bsf two bits?

blueroomelectronics · 29th October 2009, 07:35 PM

Hopefully your clock is interrupt driven, you won't loose cycles as it'll set them when the count is very low in that register.

GreenBeret · 29th October 2009, 07:43 PM

Thanks a lot... I will try it and let u know.. As i am new to PIC, it will take me couple of days to complete the full pgm and circuit...

Russ Hensel · 29th October 2009, 11:58 PM

Pic can use as little as 2ma -- no output ports, so you may not need sleep mode.

blueroomelectronics · 30th October 2009, 04:12 AM

In sleep a PIC uses much less than 2mA, think uA

GreenBeret · 1st November 2009, 05:44 PM

Hi,
Now i am facing a issue with my code. I enabled the PIE1<0> bit to enable timer1 interrupt. I am getting the interrupts for only sometimes, after that its not giving interrupt. I have a simulator software, when i test in that, i can see the PIE1<0> bit is getting cleared after some time... How this bit gets cleared automatically.. ? Pls help..

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29th October 2009, 05:02 PM	#1
GreenBeret	16F72 digital clock Hi all, i am new to PIC. I am trying to create a digital clock with 16F72 and Hitech C. I want to use timer1 in sleep mode with backup battery when the external power goes down.. I want to get precise timing for half a second to toggle second LED to make it blink once in a second. ie. half of a second in OFF condition and half of a second in ON condition so that i can see a proper blinking of 60 times in a minute. Please suggest a crystal speed that i can use for this requirement with its prescaler. I dont like to set the timer1 with a initial value because it will cause precision errors in time.. i would like to use bresenhams method for timer to get precise timing. Please suggest...

29th October 2009, 06:47 PM	#3
GreenBeret	I dont have any circuit as of now... My idea is to connect PORTB to 7segment display parallely and scan segment using PORTA. I know we can use 32.768KHz crystal, but it will take 8seconds delay to overflow. I want to use this low speed crystal because of power saving... I wanted to 0.5 second notification for second blinking...

29th October 2009, 06:54 PM	#5
blueroomelectronics	With no prescaler it should take 2 seconds to overflow. You can bsf the top two bits on the timer register to cause overflow every 0.5sec bsf will not reset the prescaler. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/

29th October 2009, 07:29 PM	#6
GreenBeret	Thanks blueroomelectronics for your help. Here i have some more doubts according to your method... 1. While setting top two bits, will i loose some instruction cycles and will it lead to precision errors..? 2. After each overflow, do i need to set the top two bit again.. meaning for each overflow, do i need to bsf two bits?

29th October 2009, 07:35 PM	#7
blueroomelectronics	Hopefully your clock is interrupt driven, you won't loose cycles as it'll set them when the count is very low in that register. __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/ Last edited by blueroomelectronics; 29th October 2009 at 07:38 PM.

29th October 2009, 07:43 PM	#8
GreenBeret	Thanks a lot... I will try it and let u know.. As i am new to PIC, it will take me couple of days to complete the full pgm and circuit...

29th October 2009, 11:58 PM	#9
Russ Hensel	Pic can use as little as 2ma -- no output ports, so you may not need sleep mode.

30th October 2009, 04:12 AM	#10
blueroomelectronics	In sleep a PIC uses much less than 2mA, think uA __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/

1st November 2009, 05:44 PM	#11
GreenBeret	Hi, Now i am facing a issue with my code. I enabled the PIE1<0> bit to enable timer1 interrupt. I am getting the interrupts for only sometimes, after that its not giving interrupt. I have a simulator software, when i test in that, i can see the PIE1<0> bit is getting cleared after some time... How this bit gets cleared automatically.. ? Pls help..