Pro PCB VFD Approx Clock

VFD Approximate Clock using a Professional PCB

Introduction

This is the "production" version of the Prototype Approximate Clock.

The features remain the same:

• 16 character starburst VFDs (bought on Ebay from Obtainium! (a quick check shows they have none left)
• an atmega168
• A6810 VFD drivers using the SPI port on the mega168
• a DS1307 RTC on the TWI port
• a LM9022 driver to generate the 24VDC required by the VFD and the 4.5VAC filament drive
• wire components and not SMDs and use nothing exotic - all parts should be readily available from UK suppliers (except the VFD of course) and in the end I used one SMD - the LM9022
• PWM to dim the display
• multi-language support (not necessarily simultaneously).

After considerable help from Nick deSmith with the board layout, I eventually placed an order with Olimex Ltd for a couple of manuafactured boards to build and fully test before looking to a larger order for gifts and for sale (these are now available).

Schematic and PCB

You should look in the "/VFD Projects/Approx Clock 2" folder.

There are two components connected by wires and so not shown on the schematic a NORPS12 LDR to sense light level for setting the display brightness and a rotary encoder with a built in push button (I used an Alps encoder) - see the Parts List below.

The boards are in the photo gallery below.

Software

The software was written entirely using C and compiled using the CodeVisionAVR compiler. The complete source code is available for download from the dropbox. Beware - C purists beware that my C is perhaps a bit idiosyncratic but I like it. However, I hope you will find the code well commented. I have included the required libraries and you may have to play with the various paths to suit your individual set up. This zip file includes the required fuse settings and compilled hex files.

With help for René Eickhoff I have a German language version available and adding more langauges is fairly straight forward. Croatian, Gaelic, French and Spanish are looking possible.

The clock software has three main modes:

1. A scrolling text message displaying the time on as a 12 hour clock, pressing the push button displays a scrolling text message giving the date.
2. A static "conventional" digit clock using numbers, pressing the button displays the date using numbers.
3. A settings mode where the clock display parameters can be selected using a Clock Menu system. In brief:
   • Set Date and Time:
     • Set DST - can be off, on (+1hr), automatic to EU rules, automatic to US Federal rules.
     • Set year (2000-2099), month, day, hour, minute, second.
   • Set Scrolling parameters:
     • The Scroll lead-in and lead-out character (including none) as "*" is used in * * * FIVE MINUTES TO EIGHT * * *
     • The number of lead in/out character (3 in this example)
     • The scroll delay between character shifts in 10mS counts - basically "scroll speed"
   • Time Formating:
     • HH-MM-SS or HH-MM display
     • Select the separator character to use, "-" in this example
     • Whether the separator is flashed on and off each second (looks good in HH-MM format)
     • Whether spaces are added to use more of the display width: 18 - 16 - 23
     • Display the number digital clock in 12 or 24 hour mode: 01:30 or 13:30
     • Supress the leading 0 on the hours digits: 09:47 or 9:47
     • The "approximate" clock granularity 5, 10 or 15 minutes - the time steps taken between changes
   • Date formatting:
     • DMY, MDY, YMD formats
     • Show the day of week as well on the text display: * * * TUESDAY, JUNE 10, 2008 * * *
     • The separator character, spaces selection and leading 0 supression as for the time display above
   • PWM dimming controls:
     • Automatic or manually set.
     • Two parameters for the LDR sensitivity and two more for the VFD PWM limits for fine adjustments.
     • Turn off the VFD filament overnight timer (with a wake up function)

All of these parameters are stored on the NVRAM space on the clock chip and are saved and loaded as required.

Photo Gallery

For Sale

At the time of preparing this web page I have some spare boards and VFDs for sale for 15 GBP for a set (one board, one VFD) contact me if you are interested. I can also supply the A6810 and LM9022 chips and a programmed AVR - all for a price of course!

All boards, VFDs, A6810 and LM9022 parts have been sold (sorry)!

Menu

The menu exists as a tree with a "top menu" which is selected using the encoder and then pressing the push button. There are then 6 sub menus and a final "return" back to the top menu. Each sub menu has a sub-sub-menu. When an item to edit is eventually selected, rotating the encoder will show the possible values. Difficult to describe with words, but intuitive to use (IMHO).

Parts List

Although all listed here, many items were bought on Ebay or were selected as I already had them to hand for instance the SB160 diodes could be replaced by many other diodes with a lower voltage rating. Obviously the component sizes and shapes only become important if you are going to reproduce the Eagle PCB layout without change or if you are going to use the available PCB. Some components are critical, most of the ICs and crystals for example. The capacitors in the power supply a closely spaced so the table below includes the required dimensions. The microcontroller expects the pulse series for the encoder used (sequence and timing) substituting a very different encoder might require code changes. Otherwise most of the components can be substituted with other types and ratings.

The Mouser and Digi-Key Parts List can be downloaded and an Excel Spreadsheet from the dropbox (with thanks to Mark Kaufman).

Notes:

1. If a 24VDC power supply is used then D1 - D5, C3 - C7 can be omitted. JP3 must be set accordingly.
2. The current software version does not address the dot or comma display so IC8 and C15 can be omitted (it would not hurt to fit the socket and C15 as a low cost compromise).
3. DC input voltage can be anywhere in the range 12 VDC to 40VDC, higher if the high voltage version of IC1 is used.
4. ISP connector is arranged as a standard Atmel 6 pin - pins 1 and 6 are marked for correct orientation.
5. The LDR can be omitted and the display brightness set manually.
6. This diode is for accidental reverse polarity protection and is not intended as a rectifier.
7. The current software does not use these jumpers, so they can both be omitted.