Multiplex / Demux

[piratepaul]

I think interfacing piggi backs with 28 double inverter MOSFETS would be a good idea, current flows through the PSU as opposed to the CD MOSFETS...
Timing diagrams, pref vidioesque, ie. moving, seems to be a good first step.

Back in a bit.

[Pauldf]

I think I need to strip the CD player down first to see if the display is common anode or common cathode.
I'll have to try and find my isolation transformer before I touch something that hurts with it live!

[piratepaul]

Hi, I meant CMOS... not mosfet... achermmm ...
I make that 2x5x28 bits, 280 bits ... You could double it ...(560 bits)... leave the second half blank and call the wire a bus... demux the CD end, mux the remote... put the kettle on, change the record, kick the toaster and let the cat out while its waiting.

[piratepaul]

Hi... this thread seems to be chilling... no prob... For those wondering, the cat complete with box gets putted at aprox

6.59999999999 am.

No hard feelings if you dont want to go ahead Pauldf... your CD your money I'm spending etc.

Tar&stuff.

[Pauldf]

Not chilling as such, am working shifts at the moment but should hopefully get more time next week, I only need the 28 bits transmitted across to replicate the inputs. It is so we can have a time display at the lighting desk which is at the back of a hall, the CD operator usually sits at the front near the stage. The producer of a show (local am dram) sometimes wants lighting changes mid track and I am useless at remembering where in the song to set the next que so if I could see the CD time position I can use the time as opposed to having to remember where in the track, especially when I don't know the song or the whole track repeats itself a lot.
When I get chance Ill open up the CD player and get the fluke in there to see what voltages I can pickup. TTL chips should be a high enough input impedance that they don't blow up the CD internals I hope!!

Cheers

Paul

[piratepaul]

yea yea, Time prob myself... TTL should be OK ... a chance you take or CMOS buffer for safety... we agree TTL should etc ... its your CD, there will be no flicker with a latch.

Tar&stuff.

[piratepaul]

You could use a 29 I/O CMOS and tap the clock from the display driver chip in the CD and forget the 555.
I think the 3 wire system is best suited to your needs. You could flip flop the whole thing so that it is on for 28x5 = 140 bits then off for 140 bits ... this is less likely to include error than a non stop sequence.
I will have to think about it (time) but you may need a mod 29 and a mod 6, 000000 and 000 can then code for off... as I said I will have a think about it.

The cat5 is likely to cause a voltage drop ... +5V at one end will be less than 5V at the other when current is drawn... and it will be. If the voltage of a 1 is less than.. (I think it is 2.7 off the top of my head). it will not work.
With a 3 wire system you could use a heavy 3 core cable... lawn mowers etc spring to mind.

Any chance of uploading the last solder of the interface to the CD (you would not cheat now would you) and the look on your face at the moment of switch on in one sequence.

Sabath b(put cat)sabath ... ... ...

Tar&stuff

[Pauldf]

Eventually got around to opening up the CD player and probing it with a fluke, unfortunately they aren't ordinary 7 segment displays in it - it is a vacuum fluorescent display I think. I probed some of the signals to it and it appears to just have a data link to the main chip so I don't think it is going to be a starter
Oh well, over to plan 2 - use a laptop with a VGA over cat 5 extender to a monitor by the lighting desk, at least that will also allow use of mp3s.

Thanks anyway

Paul

[piratepaul]

Yea thanks mate good chat ... enjoyed it... point a web cam at it ...

Look after the cat ...

Tar&stuff.

[piratepaul]

It is poss to use the cat5 and amplify the output, the idea of the 3 wires would have been to power 240VAC stuff with 2 and use the third as the data wire...

THE END.

Tar&stuff.