During the week I had little time to work and no access to a workshop, so all I could do was ordering the components and planning.
manuall y dr illing small vias is very hard, at least for me reducing number of components makes your life easyer two sided PCBs are hard to make at home, specially aligning the sides with each other
This is a 4 display module and driver before I decided to use a single shift register for two 7 segment characters.
I'll try to keep all the schematics, board designs and code up to date there.
Bellow is a list of components and modules I need to create to finish this project.
There will be 3 or 4 display modules in each of the 3 clock rows:
- Month display
- Date display - month day and year
- Time display - AM / PM LEDs, hours, colon LEDs and minutes
There might be 4 displays in one of the rows if I decide to reuse a prototype module I already made for a year display. We'll see how much time will I have and decide then.
Display driver module
This will generally contain shift registers and will have display boards solder to them. I already worked on one of the boards, however I run into problems regarding very small vias. Right now I will try to make such module using prototyping board and through-hole components to see how small can I make it. If it will turn out well, I'll use this approach for all driver modules and the main controller board, as the only tool needed is a simple soldering iron. That would allow me to work at home and will rise my chances of completing the project before the deadline.
As I lack experience with electronics, I try to keep each of the modules as simple as possible, so I don't waste too much time replacing a module if I make some mistakes in them. This rises the number of PCBs and components required, but at least I can divide problems into more manageable chunks. I guess it's my software developer side, but I can't help it.
These will be driven by AVRs (arduino mini or nano?) and will control an entire row of LED displays.
I didn't design the main controller yet, but I already have some ideas about it.
It's brain will be some arduino board. This controller will do the glue logic between input buttons, radio module, RTC and display controllers. All communication will be done through I2C.
I will use PCF8583 i2c RTC chip with a battery backed RAM. I'll use it's ram to store additional configuration, like programmed radio stations and alarm date. I don't know how this chip compares to other I2c RTCs out there, but I already used it in my previous project and I still have a bunch of unused chips on my desk (buying extra components when doing some project is a good idea!)
The realtime clock circuit will lie on the Main controller board.
This one is a bit of a challenge. I found 3 chips with I2c interface:
This is a big problem, I should have ordered the SI4703 modules a long time ago... My plan is now to order all the module types I find and see what I can do with it. If I don't get a module with RDS support, I'll have to modify my plans regarding the last display row of my clock.
I'll try to make a working display driver module. If that goes well, I'll make all the 7 segment displays and drivers this week. Then I'll work on 14 segment displays for months and RDS display.
In the mean time, I'll try to assemble all the remaining pieces of electronics I need and start thinking about the case.
I hope I still have enough time...
Whish me luck!