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Digital Master Clock with 7 Seg LED Displays & Hourly Ch

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Thread starter #61
bunghole said:
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.
 
#62
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
 
#63
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
 
Thread starter #64
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.
 
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Mike - K8LH

Well-Known Member
#65
bobledoux said:
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.
 
#66
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.
 
Thread starter #67
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.
 
Thread starter #71
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@btinternet.com/clock_electronic_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/1283/897780499_7ce751e445_b.jpg largest size is 1750x1700 from the main page here http://www.flickr.com/photos/brettoliver/897780499/ .
Brett
 

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#72
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..:$
 
Thread starter #73
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.
 

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#75
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
 
Thread starter #76
Just added a new slave to my masterclock system.
This is built in the style of a regulator and uses 3 modified quartz clock movements to display hours mins and seconds in a 12" office dial clock case.

I found my master clock could only drive 3 clock motors using the 4093b chip. I was already driving 2 slaves from this output and as this new clock had 3 seperate clock motors I have now added a "repeater". The repeater sits inside one of my clocks and can drive upto 6 clock motors.

Full details here http://uk.geocities.com/brettoliver@btinternet.com/clock_electronic_1a.htm


PS I have added a short animation showing the master driving an analogue and binary slave and electro mechanical chiming to You Tube http://www.youtube.com/watch?v=lzlPAHDf2f0
 

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#77
Hi Brett

Once again great work!! looks good.

Have you ever considered adding msf. to your master?

Mark




Just added a new slave to my masterclock system.
This is built in the style of a regulator and uses 3 modified quartz clock movements to display hours mins and seconds in a 12" office dial clock case.

I found my master clock could only drive 3 clock motors using the 4093b chip. I was already driving 2 slaves from this output and as this new clock had 3 seperate clock motors I have now added a "repeater". The repeater sits inside one of my clocks and can drive upto 6 clock motors.

Full details here Electronic Master Clock


PS I have added a short animation showing the master driving an analogue and binary slave and electro mechanical chiming to You Tube YouTube - masterclockmovie.mpeg
 
Thread starter #78
Thanks wombweller.
I would love to add MSF to my master. If there is a simple decode circuit out there that would give me a 1 sec pulse (I'm not bothered with the other time and date data) I would give it a try.

I ran the Maplin MSF clock for many years before I built my Master but the signal here is not too good and it would get lost many times a day. I have an MSF alarm clock that works well but again the signal comes and goes.

My best bet is to use an MSF pulse to sychronise my seconds pulse maybe once an hour or perhaps a day.

Anyone know of any circuits out there I could use?
 
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