Episode: 2329
Title: HPR2329: Building a Digital Clock Kit
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr2329/hpr2329.mp3
Transcribed: 2025-10-19 01:23:06

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This is HPR episode 2,329 entitled Building a Digital Clock Kit.
It is hosted by Dave Morris and is about 28 minutes long and can remain a explicit flag.
The summary is, I bought a self-built digital clock on e-mail and document the building process.
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Hello everybody. Welcome to Hacker Public Radio. My name is Dave Morris.
So today I'm doing a, I was going to say quick but I'm not very good at judging quick
when it comes to HPR shows. I'm going to do a show about a digital clock kit that I built recently.
I thought it might be of interest. So last month, this is now May, I'm recording this April 2017.
My son and I both came up with the idea of building digital clocks. We both watch a YouTube channel
bigclive.com which I've linked in the notes here and I've mentioned him when I was reviewing
some of the channels I follow. He's always messing around with electronic stuff and he built
a digital clock. I'll point you out the episode where he did this. Anyway, we both watched this
this episode and we both must have come up with the idea of building a clock of our own.
My son who found one and I've linked to it on eBay. It's the UK version of eBay but I imagine
it's available worldwide. It's a Chinese product from Shenzhen. Shenzhen, that's right, it's not
and it's currently cost $5.35 US I guess and that's about £4.18 in UK pounds and it's cost no
postage. That's the whole price. Coming from China takes a long time so you need to be patient
which I wasn't very much but got here eventually. Now there are many digital clocks on eBay and there's
loads of YouTube videos showing how to build them so you might want to. If you want to do this you
could do well to look around for other alternatives. I'm just going to tell you about mine.
Doing something like this gets you a digital clock fine but it's also an interesting project
for learning a bit of soldering. If you're not all that good at soldering this is a bit more
challenging than some of the beginner projects that you can buy in on Amazon or in electronic
shops so I thought it'd give this one a try anyway it seemed like fun. I would advise avoiding the
ones that use surface mount components. The one I've got is it's got through whole PCB so you insert
the components into the holes and solder them in there but some produce so-called SMD surface
mounted device components where you lay them on the surface with solder paste underneath them
and then use a hot air gun to do them. You can do the soldering and it's really hard I think anyway
I'm not up to that yet but my son has been building stuff that way but as a beginner thing it's quite
a challenge. So the package came in the usual sort of I think it was a plastic envelope thing with
the bubble wrap inside it. It was okay but you can imagine if anybody hit it really hard it
would smash but it arrived intact. I've got some pictures here in the long notes that show you
the various bits and pieces they're all thumbnails and the notes you need to click on them to see
the full picture and the pictures are not huge but hopefully they're clear enough.
So the components I got were a PCB, a four digit display, a perspex box to put it all in.
There were two two chips which I imagine are programmed, integrated chips,
pick chips or something like that, sockets to put them in which makes it a lot easier to
harder to destroy them that way and the usual sort of resistors and capacitors and stuff.
The USB power lead and although it says in the eBay site there's there is no battery, there is
one in the kit. It's a CR1220 lithium cell.
So I've got a picture of all the bits after I unwrap them. I also took a couple of pictures of
the PCB because I thought it looked quite nicely done. It's clearly printed, it's got a screen
printing on it so you can see all the components go, it looks quite well made.
So to build it there were some hints about how to sequence the components in the instructions
and I'll get into the instructions a bit more detail later but I just started with the resistors
being the easiest things to install anyway. So my first picture is of the first set of resistors
going into the board. I got a PCB holder for Christmas so I included that in the picture just to show
it off. The board is so small the PCB that it doesn't really fit into this holder all that well,
especially as you start to put components on it and I've got pictures of it much more populated
the PCB and you can see it's hard to get it, there's hard to find anywhere to put the grippers
of the holder onto it but I've just populated most of it, there's not a lot of components.
I didn't do a step-by-step breakdown of it, I've shown the front and the back.
The case is an interesting thing, it's got lugs that fit together and it's got bolts, nuts and
bolts that fit through it to hold it together, reasonable design but to get all of the bits
correctly aligned I found was a bit of a challenge. This is not completely obvious which way
around some of them go, some of them are obvious but some not. So I dry assembled it before building
it up and I marked the bit so it was easier to put together when the time came.
So having got all the components on the board I then needed to make sure that all of the components
were trimmed very close to the back of the PCB because that's where the display goes.
The display pins had got bent in transit because they just stuck into a bit of foam and so again
they're all aligned and through the holes took a little bit of time but once it was in and I've
got various pictures of it fitting into the populated board because all the pins pop up beside
the components you've fitted in. You have to do it in this order obviously and getting then sold
another picture of it being sold is an interesting challenge and you'd be very delicate with your
use of the sold and un. You need a really fine one too. I've got a temperature controlled one
that I bought year or so back. The clearance between the back the PCB and the display chip
was had to be really as small as possible in order for the whole thing to fit together.
That got me to the point where I could then fit the whole thing into the case which I did
are taking the protective paper off the components but even then I found that getting it all aligned
properly was very difficult. I would take some pictures of these are partly to discuss it with
my son actually of how the speaker doesn't quite fit into the hole where it's meant to go.
It fits through it but getting all the bits lined up so that it's properly aligned was a challenge.
I managed to eventually move things around and juggle them slightly in order to get it lined up
again but it was a little bit of a challenge. Two of the bits on the PCB are a light dependent
resistor and a thermistor temperature sensor and they are supposed to poke through the top of the
case. Now you'll see some pictures of this thing built elsewhere where they stick out a long,
long way and I wanted to make sure that they were fairly short that they didn't protrude too
far for fear of damage so getting that all done and aligned properly was an interesting challenge.
But it all came it did all come together as you can see from the pictures and having
gone through these various difficulties it all got assembled and power was applied and yes it worked
surprisingly. It's most delighted. I've tried to take a picture of it but because it's a flickering
device I guess cameras don't like it very much and it's also quite bright. So to mention the
instructions then they're bad. They're really bad. I haven't copied them completely but I've
taken a picture of one bit of it. Mine was a single sheet I think that's all you ever get
but it was really badly photocopied and it was incredibly hard to actually read because
of the quality of the copy. There's a diagram of the PCB which is quite helpful for knowing
where to put all the bits but it is written on the PCB itself which component to go where.
There's a table of components with code names numbers like R1 and R2 on them so these let you
know that R1 is a resistor of such and such a type and it's to go in this position. That's okay
that's fine. That didn't cause me any great problems. The written instructions are very weird
though. It's a translation of some sort. They use welding instead of soldering and many sentences
are close to meaningless and I've given you a couple of samples. It says .3. The pins with diagonal
cutting pliers cut short parentheses. This step is important close parentheses. As far as possible
avoid to resist digital tube effect beautiful. .4. Welding digital tube digital tube must pay
attention to the final or placed on the back of the device can't welding. It's like a random
word or something but I think what it's saying is you need to make sure all the component
wires are trimmed as short as possible so they don't touch the back of the display when you put it
on to the back of the PCB and also that it gives enough clearance so it fits properly.
I think that's what it's saying. That's really hard to know where those that conjunction of
English came from. So that's the instructions. The other thing is having built it you need to
and power it up you need to set up the clock properly. Now that was an interesting challenge
and I've given a detailed list of the clock setting which just in case you happen to buy one of
these will help and it might help in other cases as well because I suspect they all use pretty much
the same software underneath possibly even the same chips. I just looked around to see what the time
is and it's now 15.53 on a Monday afternoon and I've got my clock set to beep on the hour and I hope
I managed to finish this before I forget it. We shall see. I mean just whizz through the details. I've
spelt it out quite a lot of detail in the notes just in case it comes in useful for you but essentially
there are two buttons on the clock. There's one that's marked as set in the diagram and one marked
as add. The set one's at the top and the add one's at the bottom. First press gets you to
setting the time, the hour part of the time and you use the add button to increment the hours.
Press set again and then you get to change the minutes using the add button and you press set again
and you're out of the time setting and into the alarm setting. Then you press add to change the
hours of the alarm, set again and then you change the minutes of the alarm and the third part of
the alarm is you can enable or disable it. Took me a while to work that one out I can tell you.
You just press the add to enable or disable and it's shown by an LED on the bottom right corner of
the display. When the lights off the alarms off. The next setting was a total mystery I had to
actually set it to work out what it was because the instructions just make no sense at all.
This is a mode where the clock beeps on the hour. You set the start time of when it does the
beeping so it'll be off during the night and you hit set to get to that and then add changes by
incrementing the left side of the display which is the start hour. Then you hit set again and
this then changes the right side of the display which is the ending hour. So mine says 0820 so it
starts 8 in the morning and ends at 20100 which is 8pm. Then the next set press
use add to enable or disable this mode so it's on at the moment. You can tell it is on or not by
the the light has before and you press set one more time the clock's back to normal so there are
nine presses of the set key to get from the start to the end of the setting cycle and back to normal
again which again is quite useful because it's really easy to lose yourself in this thing.
It sounds simple actually now I've said it and I've worked out what it is but trying to work it
out from the instructions is a nightmare. Big Clive had a similar problem. I think his one
worked out it's being pretty similar actually now I come to think of it. So what do I think of the
clock? Well it's fine it's a clock it's not bad for the price. On the end you do get what you pay
for so it's a very basic. The timekeeping is okay though I had noticed there's a bit of drift
I might not have set it that accurately I must say but in the few weeks I've had it it's drifted
a little bit. That just got a battery back up is great because you can disconnect it from the power
and it doesn't lose the time. The battery the CR1 to 20 is not as easy to find as some but it's
it's I can see it on Amazon so it costs something like two pounds each which I've found out but they go
the clock also shows the temperature and it switches to the temperature every 30 seconds
and returns to the time display. The temperature sensor is not very accurate it reports a temperature
which I'm sure is wrong. I have my clock on top of my powered USB on my desktop and it's under one
of my monitors so it may be warmer there than elsewhere in the house but it's reading 29 degrees
centigrade right now and it's a cool day actually for a may day and the other the monitors in the
house reading around 24 23 degrees centigrade. You can't calibrate this at all so you it's not it's
not really a reliable temperature sensor. The light sensor on the the box the LDR turns the brightness
down when the ambient light level is low so at night if you keep it on which I do then it dims
quite a lot which is fine which is good. So one hole I'm pretty happy that I bought it. I think
it's it's useful and it was fun to build and it looks looks fine. You'll find a better home for
it at some point but it seems absolutely fine to me so there you go and we haven't heard it beeping
which is to the it's quite loud. It's quite a loud beep so very best that you don't. That's the end
of that then. So I hope you find that interesting and I hope you like the pictures if you can get
to look at them. Okay then bye you've been listening to Hecker Public Radio at HeckerPublicRadio.org.
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