Can two drivers share a 7-segment LED display?

The thing is, I program all day for a living and hardware is a way to get away from it. :-) I may just have to plug in the PIC programmer for this one though. The chip count is getting out of hand.

Hey, have you every heard of this really cool thing they made called a microcontroller? Maybe it's about time you did?

Other alternatives might include a CPLD? If your afraid of processors, look at the Atmel CPLD sold by Digi Key. My guess is you could do this whole thing in a

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Sheesh, antique technology. I had had a similar job 2 year ago, a custom waterflow controller, the original was at least 25 TT/HC chips, unprogrammable , got it down to an 8051, less than 4K code, and a couple of hex inverters, and still enough room to drive a 16*2 LCD if the client wants it.

Before you complain, the 8051 must be going on for 25years now! or use a PIC to do the switching!

( sorry having a bad evening, just been outbid on Ebay,sigh)

martin

Serious error. All shortcuts have disappeared. Screen. Mind. Both are blank.

You need open collector drivers.

A microcontroller would do all this at vastly reduced complexity and cost if you knew how to program it ! Most likely one chip only required.

Graham

Yup !

Bless it's little heart :-).

I recall getting some of the early *CMOS* 80C51s back in '85.

And they just keep getting better too. Have you noticed how the operation of Timer 0 and 1 seems to have vanished recently from the data sheets though ? I guess the data's simply getting too big. It's kinda assumed you know how they work these days I guess ?

Graham

"Glenn Ashmore" schreef in bericht news:FxbNd.34350$EG1.22069@lakeread04...

Hardly a chance with the components you're using. Ever had a mechanical dataswitch that was able to switch all lines of a 25 pins subd connector. Solid piece of mechanics, dimensions and weight of a boatanchor. Not very likely to fit in your panel. Relays will do a good job but you will need at least five of them, they need more space then seven 4053s and are rather expensive.

Assuming your electronics are done so far, best thing you can do is looking for smaller displays and still use two of them.

You can go for other counters. Types with a BCD output rather then decoded ones. But even then you'll need six extra chips: three quad dataselectors/multiplexers and three BCD to seven segment decoders.

Can't help but saying that this technics are obsolete this days. All you need is a 28-pins micro with the right capabilities and maybe three transistors and er... the equipment and skills of programmig it. Equipment can hardly be a problem. Depending on the contents of your wallet you can do with a handfull to some hundreds of bucks. But skills...

petrus bitbyter

Just use a CPLD for the muxes and other logic. I've used a single 7-segment display to show multiple hex digits by cycling through them.

Leon

Use a BASIC STAMP, of course. Or the new Maxim display chips.

I have resigned myself to doing it with a PIC. I have a few 16F872s left over from that remote nav light controller. Probably over kill for this but OK to experiment with. Compared to what that light switcher does this project should be simple. Plus with an MC I can tell the user why the system stopped before all the fuel was transferred.

It's just that if you only use MPLab once a year it is really hard to keep your chops.

What do you need the 'maybe' 3 transistors for btw ?

Graham

"Leon Heller" schreef in bericht news:4205b4d1$0$16583$ snipped-for-privacy@news-text.dial.pipex.com...

Leon,

It sure can be done, but... using the components given you will need a pretty large CPLD. At least sixtythree IO-pins. You need separate display drivers or a CPLD with LED driving capabilities. If you are that far, you can go all the way and also implement the counters in the CPLD. Another option may be three small CPLDs like the old 20V8 or 22V10. Remains the equipment and skills to program these things...

petrus bitbyter

Atmel ATF1508, less than $10 from digikey, 128 macrocells and enough I/O's too, in a socketable 84 pin PLCC, buy the $100 kit for it, write the software in the Free CUPL that is very easy to use, or use the 30 day trial package of pro designer and just draw the schematic.

Even though I would have no trouble doing this I would prob. use a PIC for this project instead as it is slow enough for a processor.

Well, if you have enough (21) output pins capable driving LEDs, you don't need them. But if you have to multiplex the seven segment displays, you will need one transistor/display to switch their commons.

petrus bitbyter