relay volume control

[cubezone]

Cube X200 Rev 2.0 relay volume control
this is my recent project. now ,under test..

It have two channel, each channel has 8 resistances and relays. means that it only have nine (eigth and one mute) volume steps. but i think it is enough in most condition. controled by the ATmel 89S52 microcontrol with remote and LCD .

An externally hosted image should be here but it was not working when we last tested it.

another view.

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microcontrol chip 89s52

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LED & LCD

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

emothion icon

An externally hosted image should be here but it was not working when we last tested it.

 

[AndrewT]

Hi,
any details forthcoming?

 

[Dxvideo]

I think we can get 64 steps by only 6 relays and 6 resistors. If we configure resistors in some parallel that may be realised.
For example;
If you use eight 4K7 on each relays input and when you activate 1st and 2nd relays simulaneously then you have 2K35 input resistance. And also you can set parallel 3rd and fourth and etc by this way.
May this system work? What do you say?

 

[Dxvideo]

Never mind my idea.. ********!
Sorry.

 

[Ouroboros]

If the relays have change-over contacts, you could build an R-2R ladder netwrk to give 64 level steps using 6 relays.

 

[Dxvideo]

That means my idea is not b u l l s h i t ?

 

[Ouroboros]

Do a search on Google for 'R-2R ladder network' and you'll see the principle. It's used in D/A convertors. If your audio signal is fed into the ladder network to the same place as the reference voltage is fed in the DAC application, then you'll get a binary-controlled attenuator. Obviously you'll need external logic to ensure that your relays get switched in a binary sequence.

 

[Dxvideo]

Hmm there are a lot of documents on that issue!
So you say we need relays with change over contacts? Whats that? Is it a kind of third position? Or what?
Because as I see in R-2R ladder documents they use normal three contact relays..

 

[Ouroboros]

Yes, just the normal three contacts. Normally when people talk of 'changeover contacts' they mean a switch or relay that has a 'Common' contact, a 'Normally-open' and a 'Normally-closed' contact.

 

[Dxvideo]

I see.
So we get make a real attennuator with just 6 relays and some resistors (or a ready made r-2r IC)..
This is a shiny idea..
But do you think that affects the sound quality?

 

[jleaman]

I see.
So we get make a real attennuator with just 6 relays and some resistors (or a ready made r-2r IC)..
This is a shiny idea..
But do you think that affects the sound quality?

it should not, but using some decent relays will help the sound.

 

[Tolu]

it should not, but using some decent relays will help the sound.

Do you mean reed relays? MEDER DIL 1 Form C e.g.?

Regards

 

[BrianDonegan]

http://jos.vaneijndhoven.net/switchr/index.html

Everything you need to know.

 

[Tolu]

http://jos.vaneijndhoven.net/switchr/index.html

Everything you need to know.

That do I know. But he uses the clicky ones which make a clack-noise at every vol change. Why not using reed relays?

 

[cubezone]

Thanks all above,

here is the draft of the design.

An externally hosted image should be here but it was not working when we last tested it.

now it worked as Rotary Switch ( 1 switch closed at any time) ,

further, I want to try the "2 switch closed" mode , example , relay K3 and K5 closed (R3,R4 was shorted at this time) ,etc , so , about 20 steps volume control can be done. of course, this need to calculate the value of resistance array carefully.

or mix "1 Switch closed " and "2 Switchesclosed " method to improve this work.