The rock band Chicago once asked. 'Does Anybody Really Know What Time It Is?'
With that in mind, I think we will need some sort of clock, or timer.
It can be internal to the mixer or external. It's your choice.
I am still thinking about that. (I am leaning towards an external timer/clock since I have space issues)
I have also decided to use CMOS chips. Old technology for sure, but I am an old dude. So no PICS, PUCS or any other thing you have to program.
I realize that these days there are tons of simple circuits for clocks out in cyber space. But what would we learn building those ??
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I have made several clock/timers over the years.
Years ago, I had a need to provide a PULSE every hour at exactly :05 past each hour. It was to signal a computer that the hourly network news had finished, and it was now time for the next event. It used a CMOS digital timer and worked well for several years. Then the radio station was sold and we all moved on with our lives. (and careers)
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When I built my first LARGE mixer, (the dreaded rat invested disaster in my garage) I built two clock timers. They went on each end of the console.
However, they were built on perf boards. They worked but looked like something out of Junior High Shop class.
Another option would be to buy a kit. But it does defeat the purpose of designing and building your own.
Let's put this thing together. It will give us a working model to refer back to.
HELPFUL HINT : I used headers as a 'socket' for the displays and the LED's. (We may need to rob a part or two later.)
OK, it went together with only a couple of SNAFU's. I lost a 10 MEG ohm 1/4 watt resistor. (damn those things are tiny !!!)
So I used a 1/2 watt unit that I had.
Upon powering it up, I found two issues. One was a segment on the minutes display that did not light. I traced that down to a missing trace on the board. Easy to jumper.
The other issue was one BAD display. It had 2 dead segments (In all fairness, I probably screwed the display up myself) Luckily, I had an ARDUINO kit that had a direct replacement.
It all worked like a champ !!!!
I deem the clock kit a success. I'll stick it on the shelf and leave it run. Let's see how it holds up. Then I can think about a case of some sort.
So, in a seven day period my AMAZON clock kit gained TWO seconds. Not bad results. I think it is a success.
Since this is a 24 hour clock, it will not roll over to :01. It will reset to 00:00:00 at midnight.
So I think I will use this clock in my ham shack and do a 12 hour clock for the mixer project.
Since we have this part done, let's do something I learned when I started to cook after retirement. CLEAN UP AS YOU GO ALONG.
Now that we have learned soldering and have a working clock, let's start designing and playing with chips and resistors.
We can decide on a 12 or 24 hour clock later. I decided that it has to be one or the other. A 'switchable' 12/24 clock gets too complicated and time consuming for a project like this. I may re-visit the idea down the road.
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What is the heart of any clock or timer ?????
It's the pulse you get every second. It must be consistent AND accurate.
I have three ways to get this pulse.
1) The 555 timer : Easiest to build BUT least desirable. Great for a timer, but may not be accurate over the long haul.
2) The MM5369 chip : Good and accurate. This is what I used back in the 1990's. Bad news is they are discontinued. Good news is they ARE available on EBAY from China. Don't believe what you hear on the TV news. I received my chips direct from China in about 10 days.
3) The CD4060 chip. Easy to build and ACCURATE. This 14 stage Ripple Counter is the route I am thinking about taking. But before we do that, let's build the other two as well. Then you can choose your best option.
You can also get a 60 HZ pulse from the power line, but that technology is too old and not accurate enough to even attempt. If you are interested in this method, there are plenty of diagrams available online.
But here is a quick look at a circuit that "may" work."
I have NOT tested this circuit and won't until I start that project.
The 555 Timer.
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MM5369
Now, lets look at the MM5369.
My circuit using the MM5369 came from the book by Delton T. Horn. The book disappeared years ago, but I was able to find a replacement on Amazon.
DANGER WILL ROBINSON --- There are numerous errors on some of the schematics. Proceed with CAUTION !!..
This is a circuit that I used many times building up timers for the Radio Station. It works well and is accurate. The 'heart' of the circuit is the crystal. A 3.58 MHZ crystal. It is easy to obtain, as this crystal was used in the 'color burst' section of older color TV's.
If you need more accuracy, you can replace C-1 with a variable cap. I did not get than anal.
Here is what a circuit board would look like.
I also found this circuit in a 1994 issue of Popular Electronics
You can download this issue and a TON of other old issues at :
There is also an interesting article on how to set up your shop. (Aimed more towards the 'kit' builder, this article does have a lot of good info.)
Be prepared to spend a ton of time on this site. And if you are a fan of Broadcasting History, grab an adult beverage and set aside HOURS of time. You can thank me later
So here is their circuit.
SO back to the bread board we go.
Here is our bread boarded version of the POP COM 1 HZ counter for our clock/timer using an MM5369 chip.
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