YSC-4 Electronic Clock
I’ve just completed building a small electronic clock from a kit, the YSC-4 kit from HiLetgo, which I was able to purchase from Amazon1 for under $9. My interest in this kit was to find something simple that is nevertheless good soldering practice for advanced beginners, and I was not disappointed. The kit provides practice for a number of things that students should encounter:
- an electrolytic capacitor (requires specific polarity)
- a buzzer (also has specific polarity)
- a transistor (three leads, and requires proper orientation)
- an IC socket, and the IC itself (oriented by a notch, and soldering close contacts)
- segmented display digits (orientation and close contacts)
- 2 momentary contact switches, which DO have an orientation.
This version comes with a wall-wart with USB socket and a USB cord to the power socket. Another version, which costs slightly less, has just terminal posts for the power.
It took me under an hour to assemble, even with a break for a snack. A beginner might take longer, but would have no difficulty. The kit included a piece of paper with a list of components and a circuit diagram, along with (somewhat confusing) instructions on how to set the time and alarms. The kit did not include step-by-step assembly instructions, but since the PCB is well marked it is clear what goes where, and so step-by-step instructions really are not necessary.
Perhaps the trickiest thing in this kit was the switch orientation, because it was not clear to me without testing with a meter which contacts are always joined and which are only joined when the button is pressed. Rotating the switches by 90 degrees will be the same as having the buttons always pressed down.
Some other things to note:
- This clock has a 24 hour display (no 12 hour display).
- It will chime 3 times on the hour (unless you turn that off).
- There are two alarms. When initially turned on, the time is 12:59 and the two alarms are enabled and set to 13:01 and 13:02.
- There is no back-up battery, so you have to set the time (and alarms) again if you ever unplug it.
The display is very bright, but since the segments in the segmented display are white when not lit it can be hard to read the time from the bare clock face. You can see this in the photo at the top of this post. The solution to this is to cover the display with red or grey tinted plastic, so that only the lit red segments are visible. I had a roll of red “tail light repair” tape which is 2″ wide and it fit perfectly, as shown here:
The operating instructions that came with the kit are written in English, but appear to be a direct translation from Chinese and are somewhat confusing. I found another set of instructions on the net that are also Chinese written in English, but differently. From those and my own experience I was able to put together these operating instructions:
Switch S1 (on the left) is the Menu button. An initial long press enters the first menu. The menu pages are named A, B, C, D, E, etc., and the menu letter is shown in the first digit of the display. A short press on S1 takes you to the next menu. You can only exit the menus by stepping through all of them.
In each menu, switch S2 (on the right) is the toggle/increment button. On each menu page, us it to toggle a feature on or off, or to increment a numerical value. For numerical values you can hold the button down and the count will go up automatically.
The menu pages are:
- A – Hours, from 00 to 24 (there is no 12 hour option)
- B – Minutes, from 00 to 59
- C – Hourly chime. If enabled the clock will beep 3 times on the hour, but only between 08:00 and 20:00.
- D – First Alarm on/off
- E – First Alarm hour
- F – First Alarm minutes
- G – Second Alarm on/off
- H – Second Alarm hour
- I – Second Alarm minute
If an alarm is turned off then it will skip the hour and minutes menus for that alarm.
Outside of the menus, a short press on switch S2 will change between displaying hours and minutes or displaying minutes and seconds. While the minutes and seconds are displayed, a long press on S2 will reset the seconds to zero, and then a short press on S2 will start the clock again from 00.
It appears that when an alarm is sounding there is no way to turn it off.
The chip used in this kit is an Atmel AT89C2051 microcontroller, which is capable of much more than just being a clock. The vendor (or someone) must have flashed the IC with a simple clock program for this kit. Maybe it would be possible to re-flash it to allow for 12 hour mode. Anybody up for this challenge?
Also, I tried powering it with a single 3.7 Volt coin battery, and that worked initially, but drained the battery very quickly, so it’s not really a viable option.
These instructions by clobber24 on instructables for a C51 4-Bit Clock apply, except for the power jack. That page also links to 3D printed cases (though I think I will design my own). He printed a battery case for three AAA batteries, which worked, but he does not report on battery life.
I made 3D printed case for the clock. Details to follow…