C51 4 Bits Electronic Clock kit

[kalel]

I've been looking through some cheap kits to purchase for practice (so that if something goes wrong which can always happen, it's less of an issue).

The cheapest clock I could find is $1.63 with shipping called "High Quality C51 4 Bits Electronic Clock Electronic Production Suite DIY Kits new" on Aliexpress.

Did anyone make this kit and were there any important issues that would prevent it being worth the low price?

Here's me trying to decode the description:

SCM procedures and test the inside, not another version of the program to provide electronic

No idea about this part.

"Power supply: DC3.7V-5.5V" Sounds pretty cool, a shame it's not CR 2032 compatible, but maybe with a step up or by using a cheap li-po.

Features:
 
  1. normal walking, midnight show.

Does this mean the screen only lights at dark? Or simply that since screen is lit up, you can see it in the dark as well as in the day.
Not sure...

2. sub independently adjustable;

Not sure again.

3. Time seconds correction function.

Correcting seconds? Does that simply mean that an external oscillator is used to make it accurate, or perhaps some software "correction" built-in, or something entirely else?

4. You can fine-tune the clock speed of travel time, speed adjustable 0--9 default in 5th gear.

What? I really don't understand this one. Apparently, it has 9 gears and the 5th is the default.
Anyway, I guess this isn't the speed of timing? Time should be fixed of course to remain accurate, but perhaps it displays some different information, and you can change the speed at which the information displayed on the screen changes. Either that or something else.

5. The two-way alarm, and independently set the alarm off.

You never know, could be useful.

6. The whole point of the prompts, and you can turn off the whole point of open prompts.

Don't understand this one either.

7. The interface is equipped with a battery that can power down when walking. Battery can be guaranteed only when power is greater than 3V go. Uses two AA batteries, three AA batteries, or cell phone batteries can be.

Walking probably means working? That might explain point 1 as well.

8. The countdown function can be achieved within 99 minutes countdown, countdown to the end of the alarm.

Interesting, while not necessary (and makes things more complicated to use).

9. stopwatch function, stopwatch function can be achieved, may suspend stopwatch, stopwatch cleared.
10. Counter function can be achieved, can record keystrokes. You can also record the number of external pulses.

Pretty cool.

Below are the important features:

Kit Features: A dedicated clock using 0.44-inch red LED for display;.
 
B. imported AT89C2051 as the main chip;
 
C.1.6mm thick PCB FR-4 by military-grade sheet steel, Taobao most Plate
 
  D. components small, simple installation, high success rate, not the debugger
 
E. accurate travel time, travel time error margin of error of about 3 seconds month.

Sounds really cool for the price as a practice kit that can actually be useful (a clock is always useful). Any tips or issues with this or other kits using this chip?

From: http://www.atmel.com/Images/doc0368.pdf

Features
• Compatible with MCS®-51Products
• 2K Bytes of Reprogrammable Flash Memory
– Endurance: 10,000 Write/Erase Cycles
• 2.7V to 6V Operating Range
• Fully Static Operation: 0 Hz to 24 MHz
• Two-level Program Memory Lock
• 128 x 8-bit Internal RAM
• 15 Programmable I/O Lines
• Two 16-bit Timer/Counters
• Six Interrupt Sources
• Programmable Serial UART Channel
• Direct LED Drive Outputs
• On-chip Analog Comparator
• Low-power Idle and Power-down Modes
• Green (Pb/Halide-free) Packaging Option

Seems interesting and definitely means that new firmware could be written by real experts. Not interesting in writing firmware for it though, neither have the equipment to flash it (or the knowledge).

[skarecrow]

That sounds like the same kit I bought on eBay for $1.46. Does it look like this one?

Sent from my XT1565 using Tapatalk

[tooki]

I did one of the "6-bit" C51 clock kits, and while it's good soldering practice, it's a terrible clock in the end. No battery backup, typically horrible controls... (and mine came with a 32MHz crystal mislabeled as 12MHz, so it ran at nearly triple speed until I swapped it out for a legitimately 12MHz crystal).

They don't use an RTC chip, so you're gonna need to adjust the "gear" to get it reasonably accurate.

Like so many chinese kits, they're so cheap that they're great soldering practice even if you don't end up using the device. Or source of parts, since sometimes the kits cost less than just one component in them... What you basically never get out of them is any real learning, since they never include principles of operation or source code. If you're lucky, you get the schematic.

In terms of producing a clock you'll want to use, try this kit, which I built two of an am actually really happy with: https://www.banggood.com/DIY-DS3231-Touch-Key-Control-Brightness-Adjustable-Big-Size-Dot-Matrix-Alarm-Clock-Kit-p-1120986.html

It's entirely SMD, including the entire LED matrix, which is made of 105 individual 5050 LEDs, which are 6-pin PLCCs. So maybe not as your very first kit, but it's fantastic SMD soldering practice, and the end product is a good clock that uses a highly accurate DS3231 RTC, not the crappy DS1307 found in most clock kits (if they have an RTC at all...). The only improvements I'd wish are a) source code and programming header for customizing it, and b) more options on how to feed it power -- it's got an edge-mounted mini USB jack, but if you want the cable to emerge from the back instead, you gotta hack it somehow.

[kalel]

That sounds like the same kit I bought on eBay for $1.46. Does it look like this one?

Sent from my XT1565 using Tapatalk

Yup, I think that's it. Good price you bought it for!

I did one of the "6-bit" C51 clock kits, and while it's good soldering practice, it's a terrible clock in the end. No battery backup, typically horrible controls... (and mine came with a 32MHz crystal mislabeled as 12MHz, so it ran at nearly triple speed until I swapped it out for a legitimately 12MHz crystal).

They don't use an RTC chip, so you're gonna need to adjust the "gear" to get it reasonably accurate.

Like so many chinese kits, they're so cheap that they're great soldering practice even if you don't end up using the device. Or source of parts, since sometimes the kits cost less than just one component in them... What you basically never get out of them is any real learning, since they never include principles of operation or source code. If you're lucky, you get the schematic.

In terms of producing a clock you'll want to use, try this kit, which I built two of an am actually really happy with: https://www.banggood.com/DIY-DS3231-Touch-Key-Control-Brightness-Adjustable-Big-Size-Dot-Matrix-Alarm-Clock-Kit-p-1120986.html

It's entirely SMD, including the entire LED matrix, which is made of 105 individual 5050 LEDs, which are 6-pin PLCCs. So maybe not as your very first kit, but it's fantastic SMD soldering practice, and the end product is a good clock that uses a highly accurate DS3231 RTC, not the crappy DS1307 found in most clock kits (if they have an RTC at all...). The only improvements I'd wish are a) source code and programming header for customizing it, and b) more options on how to feed it power -- it's got an edge-mounted mini USB jack, but if you want the cable to emerge from the back instead, you gotta hack it somehow.

Right, that kit looks awesome, but I'm not very good at soldering SMD parts yet (especially small resistors and such). Did you use solder paste and heat gun or oven for that? I'm not sure how to do the tiny resistors and parts with a soldering iron. Anyway for me the first kit is more suitable.

I have some questions for you though, is it at all possible to add a backup battery to it without many modifications?

I though about using a simple small Lipo cell that I can glue somewhere to the clock and which provides 3.7v (and perhaps add a microusb plug and a diode for primitive charging of a cell with built-in protection). Perhaps the microusb can also be used for power supply via USB (protected battery should cut out charging, leaving the only power going to the clock). If necessary, a switch could be added that prevents any power going to the cell. But as soon as the cell empties out, the clock will lose the time. And if it has to power the display, that will be quickly.

Edit: I saw +3v and "ground" on the quoted image. Is this perhaps a designed place to attach a cr 2032 or other 3v battery as a backup battery?

As for the learning, you are right. But there are exceptions. Simple LED flasher circuits with 2 transistors and such might be somewhat understood through following the circuit lines (edit: I think I mean vias) and reading on the internet. Furthermore, you could modify them by adding a potentiometer somewhere and seeing what happens. It would help to possibly have an oscillscope when testing oscillator circuits, but it's fair to consider that most real beginners will not have them (or a real need for them or any knowledge on using them). I thought about playing a bit with those kits as well as the simpler they are, the easier it is to change something and the higher the chance of understanding the result. Of course, with this clock circuit, there's not much to play with as it's a complete, working solution that could only be messed up. Someone could probably change the firmware, but that's not at all beginner friendly.

P.P.S. How did you test the oscillator? I don't have the equipment anyway, but just wondering what is used for checking some high frequency stuff like that.

[Ushiwaka]

...which are 6-pin PLCCs

wait a sec that package is not plcc

[tooki]

...which are 6-pin PLCCs

wait a sec that package is not plcc

Then you'll have to tell the entire SMD LED industry that it's wrong:
https://www.google.com/search?q=plcc6
https://www.google.com/search?q=plcc+led

[tooki]

That sounds like the same kit I bought on eBay for $1.46. Does it look like this one?

Sent from my XT1565 using Tapatalk

Yup, I think that's it. Good price you bought it for!

I did one of the "6-bit" C51 clock kits, and while it's good soldering practice, it's a terrible clock in the end. No battery backup, typically horrible controls... (and mine came with a 32MHz crystal mislabeled as 12MHz, so it ran at nearly triple speed until I swapped it out for a legitimately 12MHz crystal).

They don't use an RTC chip, so you're gonna need to adjust the "gear" to get it reasonably accurate.

Like so many chinese kits, they're so cheap that they're great soldering practice even if you don't end up using the device. Or source of parts, since sometimes the kits cost less than just one component in them... What you basically never get out of them is any real learning, since they never include principles of operation or source code. If you're lucky, you get the schematic.

In terms of producing a clock you'll want to use, try this kit, which I built two of an am actually really happy with: https://www.banggood.com/DIY-DS3231-Touch-Key-Control-Brightness-Adjustable-Big-Size-Dot-Matrix-Alarm-Clock-Kit-p-1120986.html

It's entirely SMD, including the entire LED matrix, which is made of 105 individual 5050 LEDs, which are 6-pin PLCCs. So maybe not as your very first kit, but it's fantastic SMD soldering practice, and the end product is a good clock that uses a highly accurate DS3231 RTC, not the crappy DS1307 found in most clock kits (if they have an RTC at all...). The only improvements I'd wish are a) source code and programming header for customizing it, and b) more options on how to feed it power -- it's got an edge-mounted mini USB jack, but if you want the cable to emerge from the back instead, you gotta hack it somehow.

Right, that kit looks awesome, but I'm not very good at soldering SMD parts yet (especially small resistors and such). Did you use solder paste and heat gun or oven for that? I'm not sure how to do the tiny resistors and parts with a soldering iron. Anyway for me the first kit is more suitable.

I have some questions for you though, is it at all possible to add a backup battery to it without many modifications?

I though about using a simple small Lipo cell that I can glue somewhere to the clock and which provides 3.7v (and perhaps add a microusb plug and a diode for primitive charging of a cell with built-in protection). Perhaps the microusb can also be used for power supply via USB (protected battery should cut out charging, leaving the only power going to the clock). If necessary, a switch could be added that prevents any power going to the cell. But as soon as the cell empties out, the clock will lose the time. And if it has to power the display, that will be quickly.

Edit: I saw +3v and "ground" on the quoted image. Is this perhaps a designed place to attach a cr 2032 or other 3v battery as a backup battery?

As for the learning, you are right. But there are exceptions. Simple LED flasher circuits with 2 transistors and such might be somewhat understood through following the circuit lines (edit: I think I mean vias) and reading on the internet. Furthermore, you could modify them by adding a potentiometer somewhere and seeing what happens. It would help to possibly have an oscillscope when testing oscillator circuits, but it's fair to consider that most real beginners will not have them (or a real need for them or any knowledge on using them). I thought about playing a bit with those kits as well as the simpler they are, the easier it is to change something and the higher the chance of understanding the result. Of course, with this clock circuit, there's not much to play with as it's a complete, working solution that could only be messed up. Someone could probably change the firmware, but that's not at all beginner friendly.

P.P.S. How did you test the oscillator? I don't have the equipment anyway, but just wondering what is used for checking some high frequency stuff like that.

Soldering the SMD clock kit isn't as hard as you think. A simple small chisel tip (mine's 1.6mm) iron works very well. Dave has done several videos on SMD soldering (including one just recently), showing how to do it with a regular soldering iron. The only real challenge, IMHO, is that you don't have component leads as alignment guides, so you must align fairly carefully when you solder down. But it's not THAT hard. Just invest in a couple of kinds of metal tweezers.

I took a closer look at the PCB on yours, and the 3V jack is labeled BT1. Between that and the, um, creative description (point 7 in it), I'm pretty certain that's a backup battery input. A CR2032 or a pair of AAs will work fine.

As for the testing, I used my oscilloscope (Rigol DS1054Z, like most beginners here). Nothing else I own could even distantly measure that kind of clock speed.

As for customization:: That's the sad thing about these Chinese kits, they're just not documented. (And what little documentation there is, is in Chinese or Chinglish.) Some of the banggood kits (like the clock I linked to) are exceptions, in that at least they've got reasonable assembly instructions. But with all these MCU-driven gadgets, without access to the source code, you can't customize anything.

[rcbuck]

tooki,

How large are the individual digits(approximately)? Also, how low can you turn the brightness? I would like to use this in the bedroom but at low brightness. At my age I have trouble making out the 18mm X  10mm digits on my current clock at night.

[kalel]

tooki,

How large are the individual digits(approximately)? Also, how low can you turn the brightness? I would like to use this in the bedroom but at low brightness. At my age I have trouble making out the 18mm X  10mm digits on my current clock at night.

I'll definitely wait for Tooki's reply as I don't have the kit, but I'm not sure if the brightness can be adjusted at all (the description is a bit of a mess). If there isn't a setting (maybe there is and I didn't notice it in the description), maybe there's a resistor somewhere that could be adjusted or turned into a potentiometer?

I also think the kit might potentially be interesting for night use, so I'm interested in the screen brightness configuration as well.

[tooki]

How large are the individual digits(approximately)? Also, how low can you turn the brightness? I would like to use this in the bedroom but at low brightness. At my age I have trouble making out the 18mm X  10mm digits on my current clock at night.

My "6-bit" one uses 0.56" (14mm) high digits. I dug mine out and hooked it up to take a pic next to a 9V battery and breadboard for scale.

It's normal brightness, I'd say. No brightness adjustment whatsoever, though I suppose you could install higher-value current-limiting resistors for the segments. (If you add resistance or a pot to the digit, then the digit brightness will vary whenever the digits have different numbers of segments lit.)

If there is a brightness setting in software, I wouldn't know, since the instructions are a single page crappy xerox in Chinese (see below). I just did a bit more googling, and found an old aliexpress listing with "English" instructions here. I've archived a PDF of the instructions below. Doesn't look promising.

I hear you about not making out small digits. I am not that old, but I've been extremely nearsighted since I was young, and have been working on making my own huge-digit alarm clock that I can read from bed without glasses. Most commercial giant-digit clocks use red displays (which I hate) up to around 2 or 3 inches, and they suck in other ways, so I wanna DIY. I've been looking at all sorts of things for the display (LED video wall modules, addressable-LED strips used to make 7-segment, LED filaments, discrete LEDs, etc etc etc.), but finally I found a supplier of gigantic 7-segments in colors beyond red: https://chelead.aliexpress.com/store/group/1-bit-digital/121968_507029236.html
I may go with 4" white, since that's easily filtered to tweak the color.

The SMD clock kit has adjustable brightness, and the digits are 68mm high.

I've built a couple of this style kit, too: https://www.aliexpress.com/item/Factory-Wholesale-Free-Shipping-DIY-4-Digit-LED-Electronic-Clock-Kit-Temperature-Light-Control-Version/32477813627.html
It's not SMD, the numbers are 30mm high, and uses an LDR to detect light and dim the display. (It's just got two brightness settings.) However, the accuracy of these things is all over the place. One runs a bit slow (not too bad, increment it by a minute or two every week), but the other runs too fast (like 5 mins a week!), and since there's no "down" button, subtracting 5 minutes means having to press "up" 55 times... That's the downside to the DS1302/DS1307 RTCs, they're very inaccurate. (The DS3231, on the other hand, is fantastic.)

[rcbuck]

tooki, I must have confused you. I was asking about the size of the digits for the DS3231 SMD clock. They appear to be about 3 inches high, which would be more than enough for me. I can see 1-1/2 inch digits with no problem. When they get below 1 inch I have problems.

I am going to order the DS3231 SMD kit. I would rather pay a little more for accuracy. Having to constantly reset the clock would be a pain.

[kalel]

I am going to order the DS3231 SMD kit. I would rather pay a little more for accuracy. Having to constantly reset the clock would be a pain.

Best of luck with the kit!

[tooki]

tooki, I must have confused you. I was asking about the size of the digits for the DS3231 SMD clock. They appear to be about 3 inches high, which would be more than enough for me. I can see 1-1/2 inch digits with no problem. When they get below 1 inch I have problems.

I am going to order the DS3231 SMD kit. I would rather pay a little more for accuracy. Having to constantly reset the clock would be a pain.

As I said in my reply, that kit's digits are 68mm high, which is 2.68".

[rcbuck]

Thanks tooki. I missed that in you post. Appears age makes it hard to see and also easy to miss entire sentences. 

[aldolo]

I've turned this clock in a timer to power on/off a device on a daily base. Maybe someone else could be interested in it.

https://github.com/aldolo69/C51CLOCK_TO_TIMER

[dbetz]

That sounds like the same kit I bought on eBay for $1.46. Does it look like this one?

Sent from my XT1565 using Tapatalk

I have exactly the same kit. I built it but it doesn't work. Was there anything not obvious that you had to do to get yours working? I get no display on the LEDs at all.

[aldolo]

hi dbetz. why don't you post a picture of your kit assembled and connected to power?

[PCB.Wiz]

 Can we have a quick poll, of who has built a working " C51 4 Bits Electronic Clock " - the 4 digit one ?

[aldolo]

2 for me

[aldolo]

have you got the instructions around? i don't recall at all how to setup the various functions. tnx

[ledtester]

About 12 maybe more years ago I bought this timer kit which used a AT89C2051:



They sold each function as a separate pre-programmed chip -- e.g. clock, stop watch, event counter, frequency counter, etc.

Note that the crystal is hidden under the IC socket. The assembly instructions said to split the socket at its ends so you could spread the two halves enough to make room for the crystal.

No buzzer, but all of the important signals are brought out via a header. The seven-segment digits have transistor drivers.

Found the original docs and schematic. The docs suggest the kit was available from at least 2002.

[ledtester]

have you got the instructions around? i don't recall at all how to setup the various functions. tnx

From the Q&A section on an Amazon page and jumping through a few links I ended up at:

https://attach01.oss-us-west-1.aliyuncs.com/IC/DIY-Manual/1765.pdf

Found via IC Station's sitemap:

http://www.icstation.com/sitemap
http://www.icstation.com/product_document/Download/1756.pdf

[aldolo]

i've found also the instruction of another of my clocks. but in chinese.... thanks to google i've got now the translation

https://github.com/aldolo69/AT89C2051_4_digit_clock

[edy]

I bought one of those cheap clock kits off eBay, soldered it and the thing never worked. It was fun soldering practice yes, I double and triple-checked all of the connections and components. A bunch of trannies seemed to be mislabelled or the wrong ones were provided (PNP vs NPN) but I was never able to figure out why it was dead when fully assembled. For $5 shipping in, it was not worth wasting more time on it. Now I have a bunch of components.

Careful not to leave these around attached to brown cylinders these days, one is liable to scare people: 

[WattsThat]

Those clocks are yeah, well, okay for soldering practice. Also good for learning 8051 core processors if you’re so inclined but you’ll need an external programmer like the TL866II or similar.

The Chinese 1 inch, 4 digit clocks that use the STC 8051 core processors are actually usable and only need a serial port to programmer. Alternative source code is available on github, here is my contribution:

https://github.com/aFewBits/stc-led-clock

There are other versions available as well, there is another version more popular than mine. No idea why