Input selector

[flyingtele]

Personally, wether I wanted one button to click through one at a time, or two to scroll up or down, or one for each input, I would use a picaxe programmable microcontroler.
I'm not sure how big they come, but the basic ones are in a 8 pin case, with larger ones available with more in and outputs. Just have each output going through a transistor or a small darlington pair to energise the relay, only limitation is the number of outputs on the chip vz number of desired selectable audio inputs.
The programming is really simple too. I do have a schematic that uses a rotary selector knob, and each input is switched by a relay, and the circuit also incorporates an LED per input so you can see what one is active. That can be found here:

http://users.otenet.gr/~athsam/pream...odular_eng.htm

The whole page is actually for a complete modular pre-amp, but the input selector may be of some interest.

[Telemin]

@Flyingtele

That still leaves the problem of having to debounce, although it is admittedly easier to do in software than in hardware, and is a more expensive route to go down. - Although I do have a soft spot for the picaxe chips having used them for my GCSE Design Technology project and various other gadgets I've made myself in the last year or two.

My suggestion would be to grab a schmitt Nand chip and a decade counter. The schmitt nand will let you debounce the switch and the decade counter lets you scroll through the inputs. The Decade counter outputs can then power the relays, through a BC548 transistor if necessary to provide the needed current.

The reason I say schmitt nand is that you can then use some nifty circuitry to stop the decade counter triggering from the turnon pulse when you switch the amp on. Not hugely important, but it means you can wire the input you use most to the first output on the decade counter.

@Simo88 If you are interested in my admittedly simple and untested design I can draw you out a schematic. And i suggest you test it on breadboard before you go ahead and solder it up as I wouldn't be able to test it myself as I don't have a schmitt Nand chip knocking around anywhere sorry.

[flyingtele]

So you think something like a 7490 IC could do the trick?

[gmphadte]

4017 can be clocked by any one, CLK or CE

[Telemin]

@Flyingtele

I'm not sure that's the right one. I would use the 4017 IC as @gmphadte says. All you would need to do is loop the first unused output back round to the reset pin and clock it off the output from the schmitt gated push switch.

You can also do some nifty little tricks with capacitors to stop the bouncing, turnon pulses and also to give a little time delay before switching the relays so that you don't click each relay open and closed as you switch from say input 1 to 4, having to open and close relays 2 and 3 on the way through.

I realise the more things you try to get this circuit to do the more sensible it becomes to use a PIC, but that still requires a blower or at least the picaxe download circuit and all the pain of programming and debugging.

[roly3055]

Imput selector (4017 and relay) and ouput protect, tested in Livewire

[roly3055]

Model in Livewire with some modifications in the loop with reset

[Telemin]

@roly3055 you beat me to a schematic but that works just as well as what I would have posted, possibly better as it does away with the schmitt chip and still debounces pretty well.

The only thing I might consider still is putting a resistor and capacitor on each of the transistor inputs so it takes them about half a second to trigger. That way it saves the relays clicking closed and open again when you scroll past them on the input selection.

I can't remember off the top of my head quite how to do it. I'll try to remember to post what i mean properly when i get home.

[JEP]

Hi simone,

I have a nice and simple schematic using an cd4028 and an uln 2004a some diodes and resistors with led indication. Its an elektuur design I slightly changed. I use it on my mark kelly controller board to switch speeds and stop. Its works nice. I will post a schematic tomorrow.

greetings roy

[diy_audio_fo]

Originally posted by Simo88
Thanks for the schemes...
It's quite difficult to read them... where can i find a copy of audioreview? is it possible to find it on the net or to order it?

I posted the schematics in so bad resolution due to the 100k image limit of this forum.

If you send me your email I can send you the whole paper in higher resolution.

The www of Audioreview is www.audioreview.it . You can ask then if they have it.