relay controlled potentiometer..

[wireman121]

Attached is what I've managed to create so far. I want to make sure I'm going in the right direction before I continue anymore...

 

[crutschow]

Generally looks ok to start.
Move the components further apart so it's easier to read their values.
Do not use diagonal lines to connect devices on the schematic. That makes an odd looking schematic.
You need to hook up power and ground to the IC of course. Also add a 0.1uF decoupling capacitor between all power pins and ground of each IC.
Any unused input (not output) pins should be tied to ground or V+, depending upon which state the pin should be for normal operation.

 

[wireman121]

OK here's where I'm at.

Could someone help me clean this up, and then I'll move over to the PCB design (I'm going to need help making the custom components in the ExpressPCB I know it....)

Thanks

 

[carbonzit]

Could someone help me clean this up [...]

As Carl said, don't use diagonal lines. (There are a couple of places where they're appropriate, but not here.)

Show connections to all parts (like your base resistors: where do they go? you must label them).

Separate your parts so the label for one part doesn't land on top of another part. Don't squish everything together like you've done. You've got plenty of room; use it.

Make your wiring look neat.

And of course, as Carl said, ground (or connect to V+) any unused inputs on your chips. Don't leave any inputs "floating". (Unused outputs can be left unconnected.)

If you're not sure how a schematic should look, there are tons and tons of them out there on the web; take a look at them.

 

[crutschow]

Another thing to generally avoid is running connecting lines through components as you did on the right. It makes the schematic cluttered and hard to read.

 

[carbonzit]

Here, take a look at the attached schematic. I took yours and started to clean it up. (Don't use this one for anything except an example!)

Notice how much easier to see everything is? You can clearly see that there is a transistor with a resistor in series with its base connected to those IC pins. Makes it much easier to design and troubleshoot.

 

[crutschow]

CZ, that looks like his original schematic.

 

[carbonzit]

CZ, that looks like his original schematic.

Not quite; notice the upper left-hand corner. (I did say I started to clean it up.)

And it was an excuse to fire up ExpressSCH for the first time and learn how to use it ...

 

[wireman121]

Looking at the PDF for the Max5457, I'm seeing that to drive vol up, vol dn, mute, shutdown I need to be going to ground......are these PNP transistors gonna do that, or do I need something thats going to convert my 30v to a ground signal? I'm working on the schematic now...cleaning everything up...

 

[wireman121]

could someone take a look at this, and the pdf for the max5457 and make sure I'm doing things right.

I dont know that I need to rest anything at voltage or ground, if I understand correctly it says its internally done?

 

[crutschow]

The 2N2222's are NPNs and they will turn on and pull the signal to ground when 30V is applied to their respective base resistors.

The inputs do have built-in pull-up resistors so you can leave unused inputs open.

You show no filter caps on the 7805 input and output, and at the chip power input, which you need. (Look at the 7805 data sheet).

Are you aware that the chip can only pass audio signals between Vdd and Vss? Thus since Vss goes to ground, the audio signal can't go below ground. So you have to bias the audio signal DC (average) level at 1/2 Vdd. This can be done as shown in the "Typical Application Circuit (Single Supply) as show on page 15 of the data sheet. (You only need one of the bottom op amps for all the circuits but you need one of the top op amps for each output.) The op amps need to be low-noise audio "rail-to-rail" input and output types. A Digikey search gave a couple page listing of such op amps.

Alternately you could use the bottom circuit on page which uses +2.5V for Vcc and -2.5V for Vss (The max total supply voltage, Vcc-Vss, across the chip is 6V). It's a more simple circuit but the disadvantage, of course, is that it requires a negative as well as a positive supply voltage.

Edit: Depending upon the impedance of the load the MAX output sees and the distance from the MAX output to the next stage, you probably need a buffer amp on the outputs, as shown.

 

[wireman121]

crutschow - totally lost me now. I'm not actually running an audio signal through it, just using it as a 10k audio taper pot to control a Bose SA-3 amp which has 2 terminals for attaching an external 10k pot.

I am going to add the filter caps and then repost to see what else I need to do before starting the PCB design - which I'm totally going to need a lot of help with....

 

[wireman121]

OK heres where I am at. I'm not sure which capacitor I need to add to the max5457 power, so if you could help with that. I removed the 7805 since I am going to use an external power source that will already be regulated. If I do use a regulator, I'm not exactly sure what I need to be attaching where beyond the 3 terminals on the regulator.

I need to get rolling on the PCB for this so I can start testing and implementing it soon, as this job is quickly approaching and I need to have a solution.

Is anyone interested in helping (or designing) from the point I'm at? I am willing to pay for the time.

 

[carbonzit]

crutschow - totally lost me now. I'm not actually running an audio signal through it, just using it as a 10k audio taper pot to control a Bose SA-3 amp which has 2 terminals for attaching an external 10k pot.

But that means you're running an audio signal through it; how else do you think the external pot controls the amp's volume? digitally?

 

[wireman121]

Actually yes. While it is running through an audio taper pot, the pot is controlling the amp's volume control digitally. There isnt actually any audio signal running through this system.

 

[wireman121]

Is there a company that I can pay to get working on this for me if no one here is interested? I feel that I have gotten to my limit as far as what I'm capable of doing properly, and I'm rapidly approaching the time when I need this to be capable of being installed... is $100 to finish the schematic and create the pcb design an acceptable offer??

 

[wireman121]

Updated.....

 

[wireman121]

Should this work out good, I'm going to look to add RS232 and IR input controls as well, but thats WAY down the road - I just want to get this PCB printed first...

 

[wireman121]

OK, so I've slowly been trying to work though this. I have the schematic pretty much finished, I think. I couldn't find a 16-pin terminal block in the component list, so I think I created it properly, but I'm not really sure on the dimensions....

I THINK all of the component layouts are correct, but I'm not 100%...Below are links to all of the components I intend to use, so if someone could double check my work I'd really appreciate it...I printed it and lined the 5457 up and I now have the correct spacing but I dont have the other components yet, so I'm really not sure on them.

I want to also make sure my whole thing is going to work, and that I'm not missing any components?

I just want to make sure everything is good before I ship it out to be printed...


**broken link removed**

Chip

Terminal Block

**broken link removed**

 

[wireman121]

Updated PCB file, I think I'm close to done?