oliverb
Member
I have a quartz controlled master clock system that has been up and runnimg now for many years see https://www.electro-tech-online.com...lock-with-7-seg-led-displays-hourly-ch.18901/ .
The clock runs fine but the secs need re-synching every few months as they start drifting. I run the clock just a bit fast so after 3 months I just hold the seconds synch button to stop the clock until it is in sync with "atomic time".
What I want to build is a circuit to keep the seconds in synch from the DCF77 signal. I have chosen the DCF77 as the reciever modules is a bit cheaper £15 rather than £25.
My initial thoughts are as follows.
Adjust my master to run just a little slow.
The DCF77 signal has 58 1 sec pulses followed by a 2sec gap.
Count the 58 pulses and when the 2 sec gap is detected sync the seconds on my master.
Looking at Hans Summers site he uses RC networks to seperate the pulses.
From my very rough diagram enclosed
I could then have 1 sec pulse stepping IC1. When 58 pulses have been received IC2 goes high. IC3 remains low until the 2 sec (> 1sec) pulse after pulse 58 is detected.
IC3 going high resets my seconds display (stepping the mins display) and also resets the quartz 1 sec count IC.
IC1 will also need to be reset (maybe with a slight delay) ready for the first of the 1 sec pulses.
If and when the radio signal is lost IC3 will not go high and my master clock will drive my clock as normal. The master clock pulse is always just behind the DCF77 will reset IC1 ready to count again when the DCF77 signal returns.
I have a DCF77 module and have been doing a few experimants and seem to have the 1 sec pulses OK. I will have a play today and see if I can detect the 2 sec pulse reliably.
I want to keep the project as basic as possible I have no facilties for PICs so am stuck with basic ICs only.
Any feedback or ideas would be appreciated.
Thanks.
Brett.
The clock runs fine but the secs need re-synching every few months as they start drifting. I run the clock just a bit fast so after 3 months I just hold the seconds synch button to stop the clock until it is in sync with "atomic time".
What I want to build is a circuit to keep the seconds in synch from the DCF77 signal. I have chosen the DCF77 as the reciever modules is a bit cheaper £15 rather than £25.
My initial thoughts are as follows.
Adjust my master to run just a little slow.
The DCF77 signal has 58 1 sec pulses followed by a 2sec gap.
Count the 58 pulses and when the 2 sec gap is detected sync the seconds on my master.
Looking at Hans Summers site he uses RC networks to seperate the pulses.
From my very rough diagram enclosed
I could then have 1 sec pulse stepping IC1. When 58 pulses have been received IC2 goes high. IC3 remains low until the 2 sec (> 1sec) pulse after pulse 58 is detected.
IC3 going high resets my seconds display (stepping the mins display) and also resets the quartz 1 sec count IC.
IC1 will also need to be reset (maybe with a slight delay) ready for the first of the 1 sec pulses.
If and when the radio signal is lost IC3 will not go high and my master clock will drive my clock as normal. The master clock pulse is always just behind the DCF77 will reset IC1 ready to count again when the DCF77 signal returns.
I have a DCF77 module and have been doing a few experimants and seem to have the 1 sec pulses OK. I will have a play today and see if I can detect the 2 sec pulse reliably.
I want to keep the project as basic as possible I have no facilties for PICs so am stuck with basic ICs only.
Any feedback or ideas would be appreciated.
Thanks.
Brett.