Hexadecimal Clock

[AileStriker]

My Final Project for my Digital Class is to Build a HexaDecimal Clock which is due on Monday (20070813) which means that I do not have a whole lot of time (less than 100hrs. I have an idea on the circuit design but the part that I am having a hard time finding is a HEX to 7-Segment Decoder/Driver. The other part that I am having trouble with is the pulse timing. The pulse timing needs to be 1.32 seconds. My problem with that is the wiring of my 555 Timer.

Does anyone know how I can decode Hex to a 7-Segment Display? If so, what device do I use?

Attached is a jpeg image of the circuit designed in MultiSim 9

 

[Shadyman]

Not sure of any device as such, you may have to use combinational logic to drive your displays. If you have trouble with this I would be willing to help!

 

[RODALCO]

Hexadecimal is counting up to 16 if I'm correct ?

You can use the old TTL 7490 and 7447 IC's for that. If you don't decode the 10 it will run up to 16 or F then inpuls up to the next decade.

 

[Shadyman]

Yes Hexadecimal is a base 16 counting system.
But do you want to display in HEX or decimal? If you want to display in decimal then yes th 7447 will do this, however,if you want to display HEX then you may need to look at alternatives, such as combinational logic.

 

[ericgibbs]

hi,
If you havn't already bought the LED's, look at this alternative.

https://www.electro-tech-online.com/custompdfs/2007/08/til311.pdf

Eric

 

[Shadyman]

Now that's a good idea, although I doubt MultiSim has included these!!!!

 

[ericgibbs]

Now that's a good idea, although I doubt MultiSim has included these!!!!

hi,
Never used MultiSim, I suppose I should download a trial version to have a look.

 

[RODALCO]

7447

From memory i'm pretty sure that a 7447 will show A-F string as well.

Easy enough to try it out with one decade to see if that set up works.

 

[blueroomelectronics]

The 7447 displays brackets and such for digits 10-15.

 

[RODALCO]

Blueroomelectronics.
Yup you are correct. just found my old TTL book.

It lists the brackets. not the letters, i was wrong here, sorry.

Thanks,
Raymond

 

[AileStriker]

Thanks for the input and i think that i will use the TIL311

 

[blueroomelectronics]

The TIL311 may be very expensive and is a power hog, I've got a few and they run HOT.

 

[AileStriker]

Then what do you suggest that i use for the decoder

 

[blueroomelectronics]

Unfortunately I'm aware of no single chip solution. Lots of solutions for a decimal clock with TTL or CMOS chips.
If you use a microcontroller it can be a single chip solution and cost less than the TTL or CMOS version.
But it's a moot point as if you've not started by now it's unlikely you'll be able to finish before Monday. How would you get parts on a Sunday?

The only way I could suggest short of using a micro would be a diode or PROM solution. A 4 to 16 decoder like a 74LS154 and a bunch of diodes in a matrix, problem there would be low current drive. The PROM solution would require an EPROM burner.

This is my Dragonfly kit. A clock either decimal, hex or octal would be eaisly done with software. There is also a clock project with TTL on this site under projects, it's alot more complex. https://www.electro-tech-online.com/threads/digital-master-clock-with-7-seg-led-displays-hourly-ch.18901/
**broken link removed**

 

[AlarmMan]

Hi,

Before you give up on your original idea try the CMOS chip CD4495. It is a hexadecimal to 7 segment driver. I've used them alot in the past. You can google for the part number for many places such as
www.4starelectronics.com.

This should get you on the right track. Personally I like the Dragon fly project board. DOn't own one but it does look good!

AlarmMan

PS While you are looking for those chips also try to get CD4520 binary up counters. There are 2 counters in each chip so it should make the total chip count alot less.

 

[blueroomelectronics]

The CD4495 may be hard to come by, 4starelectronics turned up nothing. Sounds like a nice solution though. I couldn't even find a datasheet for it.
The TIL311 are $8 each (considered cheap) as they usually sell for upwards of $20 and that's for old stock. I used TIL311s on my COSMAC ELF1802 similar to the one pictured below back in 1977.
**broken link removed**

A more conventional design like the Southern Cross Z80 (amazingly still made) uses 7 segment displays for hex but again it's done in software by the Z80 monitor program
**broken link removed**
Might be fun *and cheaper to skip the hex display and go for something really retro like binary.
**broken link removed**

 

[Hero999]

Lots of those IC have become obsolete as they've been superseded by microcontrollers.

 

[ace_alexis]

hi to every one i have a problem and i dont know how to solve it. because i have to display the hexadecimal in the 7 segment please help me

 

[ericgibbs]

hi to every one i have a problem and i dont know how to solve it. because i have to display the hexadecimal in the 7 segment please help me

hi,

By hexadecimal, do you mean 0 to 9 and 'A to F'.?