Digital Clock(Big)... Using PIC - Page 3 - Electronic Circuits Projects Diagrams Free

Hero999 · 13th May 2007, 12:22 PM

What MOSFETs are you using?

What current are you passing through them?

The chances are you don't even need logic level MOSFETs as they will be alright at low currents with a low gate voltage. Check out the datasheet.

3v0 · 13th May 2007, 02:11 PM

Quote:

My project is approx 80% completed.

The last 10% of the project takes 90% of the total project time.

demestav · 14th May 2007, 11:24 PM

Quote:

Originally Posted by Mike, K8LH

Hi Ayne,

(1) I wonder if your 4511 and your 7405 devices can source and sink the 'peak' current required to drive the displays to full brightness at a 1/6th duty cycle?

(2) What are the voltage/current ratings for the large 7-segment displays you plan to use? Some of the really large displays use series LEDs to make up the segments and you may need a higher source voltage.

May I offer an alternative driver method (below) for a full brightness display with PWM brightness control and fade-to-black capability? This method uses 8 I/O pins, common anode displays, a single MIC5821 8-bit serial-to-parallel 500-ma sinking driver IC, and 600 to 800 ma PNP source drivers.

Have fun and good luck with your project.

Mike

Excuse me if it is a stupid question, but with which software do you design these? They look REALLY nice...

Thank you

Ayne · 15th May 2007, 07:16 PM

I have changed the IDEA

Now the Idea is:
Using PIC16F877A.
Clock will show the "Time And Date And Day And Temperature(later) also"

Now i am working on Schamatic...

I will post as it will complete.

Mike, K8LH · 15th May 2007, 07:59 PM

Day-of-week may be difficult to display on 7-segment displays. I thought about using 7 discrete LEDs for one project (below).

Temperature, or Outside Temp' and Inside Temp' display modes is a good idea. I thought about adding it to my 16F88 clock using one-wire DS18B20 temperature probes since I have 3 pins left over (grin).

You need a 40 pin 16F877A?

(drawings were done using drawing tools in Excel 2000)

Ayne · 18th May 2007, 08:55 AM

I have Complete my Design.

Now i am using PIC16F877A.
20MHz Crystel.

I am not enough expert in Assembly. I have write small program like blinking LEDs in Assembly but never do any big project with it but now i an going to program this project in Assembly.

If there will be some problem in programming in Assembly i will ask u.. I mean it is only possiable with ur help.

What u say,
I should use Two seprate crystal, one for PIC clock Frequnecy and one for Clock TICK.

OR

Only one crystal For both Purpose..

Plz give me a right Direction. (Which Timer I use for which purpose i mean For Scaning purpose which Timer or For Timer TIck Which Timer)

I request to Administator.. "Plz delete all post from above this POST".. I was going to start a new Thread but i not started. I don't want to listen huge on my this request. Remain Focus on Project in this thread.

Thanks

mneary · 18th May 2007, 10:21 PM

Quote:

How to connect +5 Volts and ground to IC2(4028) and IC1(4511).

The command to use is invoke.

kybert · 1st December 2007, 06:00 PM

Quote:

Originally Posted by Mike, K8LH

Hi Ayne,

(1) I wonder if your 4511 and your 7405 devices can source and sink the 'peak' current required to drive the displays to full brightness at a 1/6th duty cycle?

(2) What are the voltage/current ratings for the large 7-segment displays you plan to use? Some of the really large displays use series LEDs to make up the segments and you may need a higher source voltage.

May I offer an alternative driver method (below) for a full brightness display with PWM brightness control and fade-to-black capability? This method uses 8 I/O pins, common anode displays, a single MIC5821 8-bit serial-to-parallel 500-ma sinking driver IC, and 600 to 800 ma PNP source drivers.

Have fun and good luck with your project.

Mike

Mike, how can this circuit have brightness control? Can you do a timeing diagram showing the PWM signal in relation to the update signals for setting the segment values?

Mike, K8LH · 1st December 2007, 07:40 PM

I use a 1 msec PWM period and I 'scan' the display columns using that 1 msec Timer 2 interrupt. The displays are blanked when the PWM signal is high at the beginning of each interrupt cycle and that's when I borrow the column driver lines RB1 and RB2 to load the MIC5821 shift register. One display column is turned on when the PWM signal goes low. Varying the PWM duty cycle between 2% and 100% provides full fade-to-black brightness control from 98% to 0%, respectively. The interrupt driver (listing below) uses 12 instruction words plus a few instructions later on to setup the SEGDAT and COLPOS variables for the next 'scan' interrupt cycle. You don't see anything in the driver code for brightness control because it's pretty much an invisible background process. Simply change the CCPR1 duty cycle register at any time in your Main program to adjust display brightness.

The green area in the drawing below is the portion of the digit or column scan interval where the display is "on" (during the PWM "off time").

Code:

;
;  The seven LED columns are 'scanned' one at a time at 1-msec
;  interrupt intervals for an overall 14.3% LED duty cycle and
;  142.85-Hz refresh rate...
;
;  A minimum PWM 'on' time of 2% guarantees a minimum window
;  of 20-usecs (80 instruction cycles) at the beginning of
;  each interrupt cycle where PWM drives the <OE> input high
;  (display off)...  This allows me to reuse the RB1 and RB2
;  column driver lines temporarily as '5821 <DAT> and <CLK>
;  lines to load the '5821 (without messing up the display)
;  before RB1 and RB2 resume their column driver duties when
;  PWM drives <OE> low (display on)...
;
;  The 2% minimum PWM 'on' time limits maximum brightness to
;  98% but the 2% loss of brightness is inperceivable
;
ISR_LED
        movlw   d'8'            ;                                 |B0
        movwf   TEMP            ; serial bit count                |B0
ISR_Load
        bcf     SERCLK          ; preset '5821 CLK line lo (RB1)  |B0
        bcf     SERDAT          ; preset '5821 DAT line lo (RB2)  |B0
        rlf     SEGDAT,F        ; shift data bit into Carry       |B0
        skpnc                   ; a '1' bit?                      |B0
        bsf     SERDAT          ; yes, set SERDAT line to 1       |B0
        bsf     SERCLK          ; clock data bit into the '5821   |B0
        decfsz  TEMP,F          ; all 8 bits sent/loaded?         |B0
        goto    ISR_Load        ; no, branch and do another       |B0
;
;  now setup Port B column drivers before PWM drives the '5821
;  <OE> pin low to turn on the segment driver outputs & display
;
;  COLPOS variable cycles through the following fixed values
;  one interrupt at a time to 'scan' the display and switches;
;
;  00000010, column 1, inverted 11111101
;  00000100, column 2, inverted 11111011
;  00001000, column 3, inverted 11110111
;  00010000, column 4, inverted 11101111
;  00100000, column 5, inverted 11011111
;  01000000, column 6, inverted 10111111
;  10000000, column 7, inverted 01111111
;
ISR_Column
        comf    COLPOS,W        ; invert bits (only 1 bit low)    |B0
        movwf   PORTB           ; setup the column drivers        |B0
;

kybert · 2nd December 2007, 08:39 PM

Ah i think i see what your doing:

When the PWM goes high

1. Set MIC5821 output to off (linked to PWM signal)
2. Clock in the required 7-seg code into the MIC5821.
3. Enable the next digit RBx line.

When the PWM goes low, the digit is shown. All other digits are off.
Repeat for each digit.

This means that each display is lit up in turn, and is on for 1/7th of the total time required to show all 7 digits as they take it in turn.

In that case, does the current to the display have to be 7 times greater than the normal If ? E.g. a 7-seg element may be rated at 25mA, so it should be driven at 175mA ?

Mike, K8LH · 2nd December 2007, 09:09 PM

Yes, that's what it's doing. I wish I could have explained it as well.

You'll find 5 to 10 ma 'average' current (35 to 70 ma 'peak') provides plenty of brightness but the circuit is certainly capable of driving the displays with 20 ma 'average' current if you need to view the displays in a brightly sunlit room.

pasanlaksiri · 16th December 2007, 06:46 PM

Quote:

Originally Posted by markelectro

You may or may not have seen this really big clock!!!

http://www.sparkfun.com/commerce/pre...p?p=GPSClock-1

Looking forward to the end result.

Mark

Holly mother !@# How much power does it needs.

Krumlink · 16th December 2007, 06:52 PM

2.76 Amps. If you even glanced at it you could see it! It jumped out at me

ThermalRunaway · 16th December 2007, 07:23 PM

Quote:

Originally Posted by markelectro

You may or may not have seen this really big clock!!!

http://www.sparkfun.com/commerce/pre...p?p=GPSClock-1

Looking forward to the end result.

Mark

That is a really big clock. I took the time to read through the entire article, what a fun place to work this must be!!!

Brian

pasanlaksiri · 16th December 2007, 07:25 PM

Quote:

Originally Posted by ThermalRunaway

That is a really big clock. I took the time to read through the entire article, what a fun place to work this must be!!!

Brian

100% agreed

. Really nice place to work

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13th May 2007, 12:22 PM	#31
Hero999	What MOSFETs are you using? What current are you passing through them? The chances are you don't even need logic level MOSFETs as they will be alright at low currents with a low gate voltage. Check out the datasheet. __________________ I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong. Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

15th May 2007, 07:16 PM	#34
Ayne	I have changed the IDEA Now the Idea is: Using PIC16F877A. Clock will show the "Time And Date And Day And Temperature(later) also" Now i am working on Schamatic... I will post as it will complete.

15th May 2007, 07:59 PM	#35
Mike, K8LH	Day-of-week may be difficult to display on 7-segment displays. I thought about using 7 discrete LEDs for one project (below). Temperature, or Outside Temp' and Inside Temp' display modes is a good idea. I thought about adding it to my 16F88 clock using one-wire DS18B20 temperature probes since I have 3 pins left over (grin). You need a 40 pin 16F877A? (drawings were done using drawing tools in Excel 2000) Last edited by Mike, K8LH; 18th May 2007 at 08:39 AM.

18th May 2007, 08:55 AM	#36
Ayne	I have Complete my Design. Now i am using PIC16F877A. 20MHz Crystel. I am not enough expert in Assembly. I have write small program like blinking LEDs in Assembly but never do any big project with it but now i an going to program this project in Assembly. If there will be some problem in programming in Assembly i will ask u.. I mean it is only possiable with ur help. What u say, I should use Two seprate crystal, one for PIC clock Frequnecy and one for Clock TICK. OR Only one crystal For both Purpose.. Plz give me a right Direction. (Which Timer I use for which purpose i mean For Scaning purpose which Timer or For Timer TIck Which Timer) I request to Administator.. "Plz delete all post from above this POST".. I was going to start a new Thread but i not started. I don't want to listen huge on my this request. Remain Focus on Project in this thread. Thanks Last edited by Ayne; 18th May 2007 at 09:00 AM.

2nd December 2007, 08:39 PM	#40
kybert	Ah i think i see what your doing: When the PWM goes high 1. Set MIC5821 output to off (linked to PWM signal) 2. Clock in the required 7-seg code into the MIC5821. 3. Enable the next digit RBx line. When the PWM goes low, the digit is shown. All other digits are off. Repeat for each digit. This means that each display is lit up in turn, and is on for 1/7th of the total time required to show all 7 digits as they take it in turn. In that case, does the current to the display have to be 7 times greater than the normal If ? E.g. a 7-seg element may be rated at 25mA, so it should be driven at 175mA ? Last edited by kybert; 2nd December 2007 at 08:43 PM.

2nd December 2007, 09:09 PM	#41
Mike, K8LH	Yes, that's what it's doing. I wish I could have explained it as well. You'll find 5 to 10 ma 'average' current (35 to 70 ma 'peak') provides plenty of brightness but the circuit is certainly capable of driving the displays with 20 ma 'average' current if you need to view the displays in a brightly sunlit room.

16th December 2007, 06:52 PM	#43
Krumlink	2.76 Amps. If you even glanced at it you could see it! It jumped out at me __________________ IF YOU WANT TO HELP FINE IF NOT PLEASE DON"T PEE IN MY CHEERO'S