Greeting earthlings.
If you follow the channel, you know that we had a jolly good time opening up an analog
clock that flew in the Soyuz and many other Russian spacecrafts.
We got it back to life, and fed it ultra-[high] precision time pulses derived from an atomic
time source, coming out of a large pile of HP equipment.
Before we return the clock to its owner, Steve Jurvetson, I wanted to build a box that combines
all the driver electronics, so that Steve can use and demonstrate his repaired clock.
The clock needs a pretty beefy source of 28V power, and the company ICStation sponsored
this episode by donating a neat 100W boost converter, which I'll also review.
So we are going to bring back the Soyuz clock to its owner Steve Jurvetson, and I wanted
to make him a little present and bring it back with a driver, so he can demonstrate
the clock to his friends.
And I made two versions of it: one is kind of the modern way with an Atmel, an ATtiny
2313 chip, and the other one is the old way, with just a TTL divider chain.
We'll see how they work, and pick one of the two to put in the final design.
So in this case it's a very simple circuit, so I didn't need much preparation.
The only thing I doodled here is the MOSFET amplifier.
So I need to make a simple pulser that has 2 Hertz pulses at 50 to 100 milliseconds length,
and then I need to amplify that so it can drive the magnet at 28 volts.
So I just used a little MOSFET transistor.
I also decided to put the three buttons for the chronometer and a little sound generator
for the alarm clock.
And that's the amount of my research, making sure I know the pinout of the clock.
And those were the diagrams for hooking up the dual divide-by-10 TTL chips, they're a
little bit tricky.
And those are simple enough that you don't really need any design.
So all you need to do is give it some positive voltage, negative voltage, put a quartz and
its two caps, and that's it.
And the signal comes out on the yellow wire.
And that's my little MOSFET amplifier.
And there are three buttons for the chronometer.
And that's about it
And for the TTL version, it's very straightforward: it's a crystal oscillator at 2 MHz and then
3 divide-by-100.
They are the 74LS390, the same chip that's used in my noodle logic for the RAM refresh
of the HP 9825.
So I just reused that.
And then you do a chain, and then at the end you have your short pulses, they go to the
same amplifier design.
And in terms of difficulty, they are really strictly equivalent.
This one is very straightforward: you just look at it and you know what it's doing.
This one has less hardware to it, but you have the software issues.
I must have hit three or four bugs: in the Eclipse IDE that wouldn't work anymore, and
the driver to flash them that wouldn't work anymore, and it's just a whole misery.
But the code is very simple obviously, it's just to make simple pulses.
And I made this magnificent cable that goes from the Russian - Soviet connector to just
an Ethernet.
That's made out of a cat5 cable obviously.
The next issue was how to power them up, because this clock is driven out of 28 Volts and it
needs quite a bit of amperage.
Not that much for the regular clock, but the electromagnet that drives this button here
for the chronometer
stop - reset
it needs several amps.
It really pulls on the supply.
As I was looking for a boost converter, the company IC station offered to send me one
for review.
It's just the right power, appears much better built than the ultra-cheap ones on eBay, and
is less than six dollars.
They also sent me an equally excellent 5V buck converter, which I'll use for powering
the logic section.
And here they are!
And that's the 28V.
Now I have to remember, 28V goes here.
And that is the 5V here.
And I put 12V in.
This is 100 watts, but only if you power it out of 12V.
You can power it out of 5V, but then you have much less current on the output.
So let's see if that works.
Yeah, it sure does.
So look at that, it even tells you what the output is here.
And you can choose to read the input voltage or the output voltage.
And it definitely can take the oomph for activating the solenoid.
So this is chronometer start - chronometer stop - chronometer reset.
All right, since I have been sponsored to the tune of twelve dollars, I thought I would
do my twelve dollars of work, and actually check if that little supply can actually do
the 100W it was supposed to do.
And so, here i have a 12V power supply.
They say that you need at least 12V to achieve 100W.
Here I have my electronic load, currently at zero.
I put a meter on here to get the actual current.
The voltage, we can reasonably read it over here, it's pretty accurate.
And here we read the voltage on the supply here.
So let's get it to 2A.
So that's 50W, or a little bit more.
Oh, here we go!
So we jumped here over to almost 5 amps.
Here we have 1.9 amps.
The power supply is starting to feel it.
And this guy is still at 28 volts, pretty good!
So we have - let's call it 5 amps.
5, Enter, 11.6 volts.
We have 58 watts.
And at the output, we have 27.9.
And thing just...
It was 1.9 right?
Enter, 1.91, times: 53 watts.
So 92 efficient.
Ah, starting to warm up a little bit, but nothing bad.
So now let's go to: current 3.2 Enter.
Yeah, that's about it.
Three point two.
So it's at 9 amps.
This thing quit also!
That's close to 100 watts here.
It's starting to feel it, and actually my cabling is not that great.
So I should take the voltage I read over here, I'm starting to lose quite a bit.
10.8, so I have 97.2 watts in, and I have 87 watts at the output.
Eh, that's not too bad: 89.5 - let's call it 90% efficiency.
But you can see it's starting to run away: the current has grown to 9.5 amps, it's going
to 10 amps pretty soon.
So, the worry here, is that it did 100 watts, but this is starting to be really hot.
Which I'm not too worried about, it's silicon underneath.
But the big problem is the cap here.
Oops, I'm going to turn it off.
The cap's not going to make it.
The cap's burning.
So, yeah, it did 100 watts for a little bit, but no, I wouldn't run it at more than 50
watts, normal usage.
So if you want to run it at 100 watts, you need to blow on it, and you definitely - that
cap won't make it - you need to put a better quality cap.
It's just totally burning.
The internal resistance is way too high on that one.
But yeah, thank you ICstation ,your little gadget works pretty well, I'm super happy
with it.
Now, the TTL version of the circuit is an amusing circuit - actually it makes too much
noise, let's turn the clock off - in that you can follow exactly what it does.
So the LS390 is two divide-by-10.
So it's a divide-by-100.
But as you know, divide-by-10 is not a symmetric thing in binary, so it's actually made by
a divide-by-two and then a divide-by-five.
And depending whether you put the divide-by-two before the divide-by-five, you have a BCD
counter.
If you put the divide-by-five before the divide-by-two, you got a bi-quinary counter.
So here is my oscillator, and I am on the first stage.
And then if you look at it, you see exactly the function table of the bi-quinary counter
here.
So my input here is at 2MHz, and the first output of the bi-quinary counter is this not-quite-symmetric
function.
but you can see, this is actually what it should be.
It should be low-high-low-high-low-low-high-low-hig.
[Yodeling] low-high-low-high-low-high!
And then the next one is actually not quite symmetric either: it's three lows and two
highs.
And then finally the last one is a bunch of lows, and just one high.
So it's even more asymmetric.
So that's a divide-by-five, so it gets from 2 Mhz all the way down to 400 kHz.
And then I feed it to the divide-by-two.
So, if I get myself after the divide by two over here, I should get a nice squarish waveform.
And you can see, it's a nice square wave.
And it's now a tenth of the input: it's 200 kilohertz.
Then I go on the other side of the circuit, I divide another time by 10.
This is 20 kilohertz.
Then I go to the other side of the circuit and I should now be another divide-by-10.
And this is 200 hertz.
And then I go over here, and I'm now 20 Hz.
And in the last circuit, I use it in BCD count.
So I have the divide-by-two first, and the quinary part afterwards.
So it gives me nice and short pulses: I take this as an advantage, that it's not symmetric.
So here you go, this is what feeds the amplifier and turns on the clock.
And once you're done with the prototype, I just take one of those little boards from
Adafruit, and they are kind of a perma-proto.
It's just not worth it to make a PCB for a one-off, so I'll just solder that design onto
this board, and this one onto this board.
And I think I'll just, since they are equivalent, I'll use this one: it takes less space.
If I were to put it in a transparent case, I would probably use this design, because
it's so beautiful.
You can explain what it does.
But in this case it's going to be hidden, so I think I'm going to use this design.
And I also want to add one more thing, which is the alarm sound.
And I found this little cute board for generating sounds from Adafruit.
So I added the last piece which is the sound board for the alarm.
We'll see how that works.
[Clock beeps]
[Cuckoo sings]
[Soyuz launch rumble]
All right my boards are now soldered on perma-protos.
There, it looks like it just popped from the computer into reality!
All right it's all in the box.
And as usual most of the work in projects like these are not the electronics, they are
the mechanicals, and putting it all in a box ,with buttons that work, making all the holes.
And here you have it, you can demonstrate your clock!
And you have the control of the chronometer.
Let's start - and the chronometer goes.
And as you expect, stop - reset.
And here you can choose whatever sound you want for the alarm.
All right I think my gift is ready.
See you in the next episode, where we'll get to present it to Steve, and have a peek at
his amazing collection!