It seems a couple people are interested in building the novelty 1-chip clock so I started building a prototype on a Radio Shack proto' board using #30 Kynar wire-wrap wire. What a pain (grin). I've started wiring the display section of the board per the little drawing below and it occurred to me that one or more of you chaps are probably pretty good at laying out single-sided boards for manufacturing at home. Anyone care to take a stab at it? This is the foil side. The LED single-inline sockets, transistors, discrete LEDs, and diodes are all installed on the other side of the board and will sit underneath the dual-digit LEDs. The PIC, switches, speaker, and relay will be located on the component side of the board too, below the display. I just haven't gotten that far yet.

Later, Mike

Attached Images

Clock-1v2 wiring.PNG (279.9 KB, 286 views)

 

Even at a glance, I can tell it's going to be impossible to do most of that layout in a single layer without a lot of jumpers - just looking at the red, pink, blue, green, and yellow wires connecting all those header pins, forget about a "challenge", it's just plain impossible. You could probably run one down the outside edge of the header, and maybe snake another through between some pins, but there's no way you're getting all 5 of those in there.

Now, as for the challenge of minimizing the number of jumpers required, that's another story... but I expect you're still going to end up with a LOT - this circuit is simply NOT suited for a good single-sided layout, by its very nature.
Though, it looks like it would be very well suited to a double-sided layout...

__________________
EEgeek.net

 

And be prepared for a lot of vias. I made this display board with for digits and it was a good reminder how nice LCD displays are to work with. This board has 2 2-digit 7 segment displays, two switches, and a 16x1 header.

3v0

This is the Mondo SuperProbe. Please, no feedback required on the ceramic osc soldered to the PIC. It is a work in progress. If I build this again I am going to modify the code and replaced the LEDs with a 1 x 24 Character LCD Display Module AllElectronics. http://www.allelectronics.com/cgi-bi..._X_1_LCD_.html They are under $2. It looks like the customers at AllElectronics have figured out how to interface to this display in a I2C mode.

Attached Images

	Eagle.jpg (81.5 KB, 78 views)
	Probe.JPG (42.9 KB, 83 views)

 

3v0's bus approach down the center of the displays seems the most sane method, and you're be using a lot of jumper wires, or a second layer.

great idea with the 2 board approach, display daughter board, and logic mainboard.

__________________
If you don't have a planet, what good are gold bars?

want to contact me directly? gmail gordonthree
check out my project website: http://projects.dimension-x.net
Favorite numbers:
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

 

This can be done without a huge number of jumpers. I don't have the display defined in eagle and don't have the time right now but here is how I would go about it. This is the top part of the display connected with only one jumper.

Maybe someone could expand on this weaving idea.

Mike.

Attached Images

display.gif (7.4 KB, 88 views)

 

Hmm, didn't really notice before, but the displays are nice and symmetrical about the center - the 4 pins on the left of each side are mirrored from the layout of the other 4... that DOES make the layout a lot easier - good catch Pommie.

__________________
EEgeek.net

 

Mike,

The A-G bus is shared with the RB0-RB6 7-seg common anode gates. How are you gating the segments and displaying the correct digits at the same time? I first thought you might be utilizing the fact that some of the digits only show 0-2, 0-4, 0-5, and 0-9. Since the combination of some gates being turned off forces the segments of particular digits to be turned off, those particular segments never need to be displayed because they are not in that digits range such as 0-2 for the first digit. Is this the case?

 

Donniedj,

Mike came up with a charlieplex type scheme which he described somewhere else. I can't find it at the moment. The secret to the way it works is the line labeled X in the diagram above. The X line replaces the segment line that corresponds to the anode gate line. So, in the left most display the X line will be connected to the A segment replacing RB0. To display a number on the left most display segments that are to be lit are driven low, all other segments are set to input and RB0 is driven high. The same happens for the next display but now X is segment B and RB1 is driven high.

Mike.

 

Mike's got the right idea. The diagram below may help. Each Port B line serves as both a segment driver and as a column driver. The RB0 pin drives the common anode driver transistor on the first display and all of the 'A' segment lines on the other displays. When the first display is being driven "on" by RB0 then the 'A' segment on that display must be driven by the 'X' line which I call the "float" line.

Attached Images

Charlieplexed Display Wiring Notes.JPG (181.0 KB, 63 views)

 

Aaah I see. I can understand how decades of fueling the 7-segment display industry could evolved into such a clever scheme to get a leg up over the eternal pin count enemy. I was thinking that if Mike K8LH thought this all up on his own, why would he need help with a less mentally challenging task of a layout.

I always make all surface mount boards and single sided. So the question of this being a challenge is non existent because for me its mandatory. I would use the suggested weaving techniques along with minumim jumpers by using called out resistors as jumpers and the foot prints of mosfet drivers and jumpers.

 

It's not so much that I need help as it is that I just don't have the facilities to make my own single sided boards.

I'll publish the Clock design and code in the <Projects> forum for those few people who asked me to do so, along with my crude Radio Shack protoboard version, and I thought it would be nice to show a single-sided pcb layout for those people who have the capability to make their own boards.

Thanks for the input guys...

 

Mike,

Where do you get those dual displays from? The only ones I can find have the segments repeated rather than mirrored. If I get time, I might have a go at a single sided layout. If anyone has found a library with a display like the one Mike uses, a link would be appreciated.

Mike.

 

I'm using Fairchild MSD4410C (0.40", CA, Green) or MSD4910C (0.40", CA, HER) on this prototype.

I also have some Fairchild 0.56" dual displays with similar wiring pattern running on other projects; MAN6410E (CA, Green), MAN6910E (CA, HER).

<added>

Sorry, I'm wrong about the 0.56" display pattern (below). It's quite different.

Attached Images

L56.PNG (38.5 KB, 35 views)

 

Mike, K8LH

Plz share the code here (if u don't mind).

I want to make clock similar to this but with big 7-Segment Display.

I will make my self a Big 7 Segment Display with LEDs.

Thanks.

 

I want to make Real time clock using PIC16F877A.( Clock Frequency 20 MHz.)

I want to ask that TMR0 or TMR1 or TMR2 interrupt is not enough accurate for time(1 Second)...

Or What is the best way for making an accurate time delay???

Thanks.