Digital Master Clock with 7 Seg LED Displays & Hourly Ch - Page 5 - Electronic Circuits Projects Diagrams Free

oliverb · 24th February 2007, 05:56 AM

Quote:

Originally Posted by bunghole

hello, i saw the parts list and the diagram. are the parts list for the diagrams?

ta

Yes the part lists are for the diagrams and should be 99% correct so should be used as a guide only.

Brett.

bunghole · 24th February 2007, 06:01 AM

hello, if you had this running and the power got cut of, how would you put in a backup battery if you need one, into the circuit

bunghole · 24th February 2007, 06:55 AM

oh yeah...i forgot something...when you build and turn it on do you have to adjust anything so it works like a normal clock, and if you do what do you adjust?

ta

oliverb · 24th February 2007, 08:09 AM

Battery backup should not be a problem.
Just build a battery backed up PSU try this forum and use as the main power source. I imagine a 6V system should work.
If you are running slaves and chimes you would of course require a bit more power from the back up battery..

The clock will run as a normal clock and just needs time setting and chime/ 30sec clock pulse sync on power up. This should take about a min to complete.

Brett.

Mike, K8LH · 25th February 2007, 10:32 AM

Quote:

Originally Posted by bobledoux

Its been an interesting project. I've been impressed with the consistency of a regular microprocessor crystal at room temperature. In my first controller I unsuccessfully tried to vary the crystal frequency by using a variable capacitor in the crystal line. I've since decided that changing the delay period in software is a better approach.

I believe it's a better approach too. It seems you have much finer control tuning that "heartbeat" signal compared to a ceramic trimmer capacitor in the oscillator circuit. I'm experiencing 'drift' of less than 1 second/month and it seems my quarterly adjustments now are just chasing temperature drift and crystal aging.

I'd also like to mention a Maxim/Dallas chip that may be of interest. It's the DS3231 Extremely Accurate I2C-Integrated RTC/TCXO/Crystal and it boasts accuracy of ±2-ppm over the 0°C to +40°C temperature range and ±3.5-ppm over the -40°C to +85°C temperature range. It's a 3.3 volt chip in an SOIC-16 package with a programmable frequency square-wave output that I suspect might be very handy as a precision time base in some 3.3 volt PIC projects.

bobledoux · 25th February 2007, 02:26 PM

Hi Mike--

Your Excel diagrams keep getting more pretty.

I decided to track the daily error in my clock over the past week. After seven days the clock accumulative error was .087 seconds. The daily error was much less. I fed the WWV signal into my oscilloscope through an MFJ 751B audio filter. The clock pulse was fed into the other trace. My Tek scope allows me to sample the two pulses and measure the time delay between them.

The error isn't quite random. The graph appears to generate an error of about a quarter of a second too fast per month.

This is using a plain 4mhz microprocessor crystal at ambient temperature. My electronics lab also is the laundry, so the clothes dryer raises the room temperature with every load. The room temperature stays about 20 degrees C during the winter. Even with air conditioning it will go up to about 22C during the summer. I'll see how the error changes with the seasons.

I considered using the Dallas DS32KHZ TCXO which is rated for plus or minus 1 minute per year between 0 and 40 degrees C. But it was difficult to find. With my success using a regular crystal I won't go for more elegant oscillators.

The calibration process was simple. Early in the morning I would manually advance the clock at the same moment the WWV minute tone was heard. The next morning I would listen for the error between the two signals, and reprogram the PIC to eliminate the error. If there appeared to be no error the next day I let the program continue running. The error multiplies over the days so the longer I waited the smaller corrections needed to be. Eventually, the point was reached where the error appeared to be random.

This process does not require an oscilloscope or other fancy equipment. It takes a receiver for WWV and a way to monitor the clock pulse. For my equipment, the slave clock goes "clunk" every minute and the driver has a seconds LED.

oliverb · 25th February 2007, 03:23 PM

I agree this looks like a good solution to the problem. Using a trimmer capacitor you just can't move the plates in small enough stages to achive your levals of precision.

I did think of attaching a pointer to the screw on the trimmer to amplify its movements but in the end just made adjustments and compaired it to my atomic clock every day. As the clock got closer to true speed I just waited for a week to compair it.

At the start of the project I tried using a much higher frequency crystal the theory being it would take much larger turns on the trimmer to achive the same levals of adjustments. I had to abandon it as I could not get a stable frequency.

As it stands now I adjust the clock using the pause button when the error gets over a half second about once a month or so.

Brett.

Narendrababu · 15th April 2007, 10:28 AM

Quote:

Originally Posted by saeeddavish

Dear sir
I want to build a big led digital clock with seconds display.kindly send me a full schematic diagrams of digital led clock.

I want use this clock for marketingl

usmankhan · 19th June 2007, 09:42 AM

hello,
your clock circuit , but its very complicated, i need easy timer or counter circuit
usman khan

usmankhan · 19th June 2007, 09:44 AM

please give me the circuit inwhich the 555 timer used in timer circuit
plz help me

oliverb · 29th July 2007, 07:55 AM

Picture of my Master Clock System including 3 analogue slaves and 1 binary slave.

The diagram for the Binary clock I made in 1997 is on this page http://uk.geocities.com/brettoliver@...ctronic_1a.htm

There is a short animation of the binary slave working (the clock steps from 13:59 & 55secs to 14:00 & 5 secs) as well as a larger still of this clock.

If you want to see a larger picture of the binary clock it can be viewed or download from my flickr site here http://farm2.static.flickr.com/1283/...e751e445_b.jpg largest size is 1750x1700 from the main page here http://www.flickr.com/photos/brettoliver/897780499/ .
Brett

rohaan · 23rd September 2007, 05:15 PM

hey guyz!!
could u plz tell me...???
that how to show Am/Pm in 12 hour digital ckock by using fliplflop only in this portion..
as i am using counters for hours & seconds& minutes...
but what to do to show ap/am ????
m bit confused plz guys help me out..:$

oliverb · 25th September 2007, 09:48 PM

Here a couple of pics of the slave bell installation in my Longcase clock.

Note the chime is syncronised to my master but the Longcase clock runs via it's own movement. The advantage of this is I can turn the chime off at night from a switch in my master clock.

pasanlaksiri · 1st October 2007, 02:34 AM

Holly amigo! It has lots of circuitry.

But superb.

goldig · 1st October 2007, 04:17 PM

Gentlemen,

i am student of electrical engineering B.Sc.(3rd year).

instrutor has assigned us SAMPLE AND HOLD project , without given us any information. so please help me in this project ,with brief discription about this project and project components.

i have little idea that we may us FET as switch(will help in sampling of signal and we will give it two inputs: one is under observtion signal and other is square wave as impluse for sampling). For holding we will use ,a capacitor.

so these all was my unrefined information . so please help me with some simple report and project circuit of SAMPLE AND HOLD.

WITH BEST REGARDS,
Goldig

24th February 2007, 06:01 AM	(permalink)
bunghole Experienced Member	hello, if you had this running and the power got cut of, how would you put in a backup battery if you need one, into the circuit __________________ Every little bit counts! It works with money, and it works with electronics!

24th February 2007, 06:55 AM	(permalink)
bunghole Experienced Member	oh yeah...i forgot something...when you build and turn it on do you have to adjust anything so it works like a normal clock, and if you do what do you adjust? ta __________________ Every little bit counts! It works with money, and it works with electronics!

24th February 2007, 08:09 AM	(permalink)
oliverb Experienced Member	Battery backup should not be a problem. Just build a battery backed up PSU try this forum and use as the main power source. I imagine a 6V system should work. If you are running slaves and chimes you would of course require a bit more power from the back up battery.. The clock will run as a normal clock and just needs time setting and chime/ 30sec clock pulse sync on power up. This should take about a min to complete. Brett. Last edited by oliverb; 24th February 2007 at 02:21 PM.

1st October 2007, 02:34 AM	(permalink)
pasanlaksiri Experienced Member	Holly amigo! It has lots of circuitry. But superb. __________________ My home made 2.1 System Nokia 3310 Lcd & Pic12F629 3 channel IR remote Controller Project using 12F Pic Pasan...

1st October 2007, 04:17 PM	(permalink)
goldig New Member	SAMPLE and HOLD project Gentlemen, i am student of electrical engineering B.Sc.(3rd year). instrutor has assigned us SAMPLE AND HOLD project , without given us any information. so please help me in this project ,with brief discription about this project and project components. i have little idea that we may us FET as switch(will help in sampling of signal and we will give it two inputs: one is under observtion signal and other is square wave as impluse for sampling). For holding we will use ,a capacitor. so these all was my unrefined information . so please help me with some simple report and project circuit of SAMPLE AND HOLD. WITH BEST REGARDS, Goldig

25th February 2007, 02:26 PM	(permalink)
bobledoux Experienced Member	Hi Mike-- Your Excel diagrams keep getting more pretty. I decided to track the daily error in my clock over the past week. After seven days the clock accumulative error was .087 seconds. The daily error was much less. I fed the WWV signal into my oscilloscope through an MFJ 751B audio filter. The clock pulse was fed into the other trace. My Tek scope allows me to sample the two pulses and measure the time delay between them. The error isn't quite random. The graph appears to generate an error of about a quarter of a second too fast per month. This is using a plain 4mhz microprocessor crystal at ambient temperature. My electronics lab also is the laundry, so the clothes dryer raises the room temperature with every load. The room temperature stays about 20 degrees C during the winter. Even with air conditioning it will go up to about 22C during the summer. I'll see how the error changes with the seasons. I considered using the Dallas DS32KHZ TCXO which is rated for plus or minus 1 minute per year between 0 and 40 degrees C. But it was difficult to find. With my success using a regular crystal I won't go for more elegant oscillators. The calibration process was simple. Early in the morning I would manually advance the clock at the same moment the WWV minute tone was heard. The next morning I would listen for the error between the two signals, and reprogram the PIC to eliminate the error. If there appeared to be no error the next day I let the program continue running. The error multiplies over the days so the longer I waited the smaller corrections needed to be. Eventually, the point was reached where the error appeared to be random. This process does not require an oscilloscope or other fancy equipment. It takes a receiver for WWV and a way to monitor the clock pulse. For my equipment, the slave clock goes "clunk" every minute and the driver has a seconds LED.

25th February 2007, 03:23 PM	(permalink)
oliverb Experienced Member	I agree this looks like a good solution to the problem. Using a trimmer capacitor you just can't move the plates in small enough stages to achive your levals of precision. I did think of attaching a pointer to the screw on the trimmer to amplify its movements but in the end just made adjustments and compaired it to my atomic clock every day. As the clock got closer to true speed I just waited for a week to compair it. At the start of the project I tried using a much higher frequency crystal the theory being it would take much larger turns on the trimmer to achive the same levals of adjustments. I had to abandon it as I could not get a stable frequency. As it stands now I adjust the clock using the pause button when the error gets over a half second about once a month or so. Brett.

19th June 2007, 09:42 AM	(permalink)
usmankhan New Member	hello, your clock circuit , but its very complicated, i need easy timer or counter circuit usman khan

19th June 2007, 09:44 AM	(permalink)
usmankhan New Member	please give me the circuit inwhich the 555 timer used in timer circuit plz help me

23rd September 2007, 05:15 PM	(permalink)
rohaan Experienced Member	hey guyz!! could u plz tell me...??? that how to show Am/Pm in 12 hour digital ckock by using fliplflop only in this portion.. as i am using counters for hours & seconds& minutes... but what to do to show ap/am ???? m bit confused plz guys help me out..:$

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