Building an AV switchbox - electronic or analogue switching?

Check out the Motorola MC14495.

 

I saw that, but it's not as complicated as you seem to be fearing - once you have the truth table, just get some veroboard and put diodes in each position where there is a '1' in the table - the strips on the board are the output lines, and then you can put another piece of veroboard on the top at 90 degrees to connect all the select lines together. Assuming you have 2 14 seg displays and 4 modes, the whole thing will take up less than 3" x 0.5" on the board. The only drawback with this approach is that you need to be sure you get it right before you solder the top board down :smile-new:

 

I don't remember what 4xxx series CMOS is for binary to 7 segment LED but for TTL series, you want 7447. 4 bit binary input to drive a 7 segment LED.

TTL and CMOS don't always play nice with each other so try to find CMOS version if you are using CMOS chips inside that switch box.

 

Looks like Element 14 doesn't stock the above chip. A few eBay and Aliexpress vendors carry it, but the going price is about $7 a pop.

It would be cheaper to use a PIC/ATmega/ATtiny with a multi-digit driver like the ICM7211AMIPLZ.

Edit: Sadly, wilykat, all the 7447s I found only show digits 0-9, and nothing/garbage for input values 10-15. We need one that shows A-F.

I thought of the 7447, but suggested the Motorola for this reason.

 

There is an old Nat Semi part that displays hex, too - DM9368? But I think all the parts like that are going to be EOL and only available from surplus sources because all the modern stuff uses MCUs and programmable logic.

 

One could use an MCU and shift registers too, that would be quite cost effective.

 

There is a rather nice TI chip that has a 16 bit shift register and constant-current outputs - TLC5926, I think - one of those in conjunction with some high-side drivers would be a good solution for driving multiplexed 14-seg displays. Sadly, the OP has specified "no MCUs", so I guess that's a non-solution in this case.

 

Mm. Everything's I2C now, easy if you're using an MCU!

The DM9368 can be got on eBay from Hong Kong for about $7: http://www.ebay.com.au/sch/i.html?_sacat=0&_from=R40&_nkw=DM9368&LH_PrefLoc=2&_sop=15

So that's an option.

But once you have that chip, one each for the other two digits, and three binary encoders, the chip count is getting rather high.

 

Thanks again for all the help guys!

@RetroSwim: That Motorolla IC will be perfect, and cost isn't too bad off eBay so it should suit accordingly.

@TriMesh: Thanks for going into more detail - given I'd be looking at 7x 14 segment displays for what I imagined at first, I think the setup would be a little bit too tricky for me to nut out. I personally really like the idea of integrating some micro controllers running some code, but I don't think I have the mental capacity at this stage to learn how they work and how best to program them. I've done some reading on the concept ever since RetroSwim showed off his excellent solution, but I can't seem to get there.

As a result, I'm a bit jealous of the expertise being shared in this thread - definitely feeling a bit noobish

 

http://www.maximintegrated.com/datasheet/index.mvp/id/1002

single 16 channel or dual 8 channel bidirectional analog switch, would those be good enough to handle high bandwidth for video? I'm also building a large switch box since no one makes one with at least 12 S-Video support. Just 4 of that 16-in-1 chip (one for Chroma, one for Luma, one for L, and one for R, plus composite video for NES and Intellivision since neither supports native S-Video even with mod)

 

MangledLed, how goes your switcharoo?

Yeah, that definitely looks like it will do what you want it to do!

 

I can't remember if I posted earlier but I've decided to re-do my diagram - too many wire links everywhere with the way I laid it out! The new one is still a bit massive/messy, but includes the new 7-segment displays and a few other things. Just have to finish adding the component and RGB parts then I'll be done! Well, the designing anyhows - the build hasn't started yet... but the problem is that I'm itching to blow some money on games instead of saving for all the components for the switch

 

I've been thinking about your display situation a bit.

And the more I think about it, the more a microcontroller seems to fit the bill. You could even do it with a little ATtiny (or PIC16F if that floats your boat), and some shift registers.