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C51 4 Bits Electronic Clock kit
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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:


--- Quote ---SCM procedures and test the inside, not another version of the program to provide electronic
--- End quote ---

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.


--- Quote ---Features:
 
  1. normal walking, midnight show.
--- End quote ---

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...


--- Quote ---2. sub independently adjustable;
--- End quote ---

Not sure again.


--- Quote ---3. Time seconds correction function.
--- End quote ---

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?


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

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.


--- Quote ---5. The two-way alarm, and independently set the alarm off.
--- End quote ---
You never know, could be useful.


--- Quote ---6. The whole point of the prompts, and you can turn off the whole point of open prompts.
--- End quote ---

Don't understand this one either.


--- Quote ---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.
--- End quote ---

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


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

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


--- Quote ---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.
--- End quote ---

Pretty cool.

Below are the important features:


--- Quote ---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.
--- End quote ---


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

--- Quote ---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
--- End quote ---

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:

--- Quote from: skarecrow on June 07, 2017, 04:34:43 pm ---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

--- End quote ---

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


--- Quote from: tooki on June 08, 2017, 01:27:10 am ---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.

--- End quote ---

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:

--- Quote from: tooki on June 08, 2017, 01:27:10 am ---...which are 6-pin PLCCs

--- End quote ---

wait a sec that package is not plcc
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