Engineering How would an alarm button work in a bathroom scale?

[Lord Popo]

Homework Statement

I am given a bathroom scale that I have to reverse engineer and beneath the bathroom scale, there is a button that sets an alarm for 24 hours from when you pressed it so that it can remind you the next day at that same time to check your weight. On the circuit board, there is the button that sets off the alarm and there is a soundbox where the alarm noise comes from. How are the seconds measured? Is it in cycles, what units would they be in? How does the scale know when 24 hours is up and how does it display that information onto the LCD screen? And when the alarm, rings, it can be turned off as soon as you step on the scale and if not the alarm will sound for 20 seconds; how does this function work?

Relevant Equations

No relevant equations are known.

All I know is that when you press the button, the LCD icon displays an alarm icon which indicates the alarm has been programmed to sound at the exact time every 24 hours.

 

[berkeman]

So from your Profile page, it looks like you are starting your EE undergrad?

How much do you know about microcontrollers so far? Do you have any experience with Arduino or PIC processors or Raspberry Pi microprocessors? How much programming have you learned so far?

There are pretty simple circuits to use for clock timing circuits, but if you want to add extra functions onto those simple timing circuits, it's usually best to use a PIC or other inexpensive micontroller that incorporates simple low-power timing with the ability to process interrupts (after some number of seconds, etc.).

Are there any small tubular crystals on that PCBA labeled with 32.768? It would be about 2mm in diameter and 10mm long... If there is such a crystal on that PC board, can you do a little Google search to figure out what is important about that number, and why that crystal is on that board?

Also, if you look at this application circuit for a simple timing circuit designed with a common CMOS IC, can you understand what it is doing and how you might use it as a building block for this circuit's functionality?

https://assets.nexperia.com/documents/data-sheet/74HC_HCT4060_Q100.pdf