Jump to content

How to push the volume?


Henning
 Share

Recommended Posts

Ok, this is my car stereo:

 

P4040036.thumb.JPG.ff236926983523ee3962b9d8baaecd4d.JPG

 

A cheap chinese brand and it's some temperature sensitive. I haven't learnt yet how to switch it off (no need), but it has got a USB-port, enough punch and the sound is ok for me.

 

The volume is controlled by a rotating knob without stops. Turning the knob clockwise the volume rises until the stereo is at its maximum. There, the knob doesn't stop, it can be rotated as long as you want.

 

It's the same the other way: turning the knob against the clock, at some point the volume is off but the knob can be turned on- as long as you want.

 

I think any newer car stereo has got this kind of volume control. Even the Becker Mexico retro device is designed like this with a shivering or rattling feeling.

 

Now I'd like to know: how does this regulator work? It can't be a standard potentiometer since it has no stops. So my guess is that there are two push-buttons inside activated by a kind of pendulum that's pushing the buttons by its inertance strained and released by a step-spring or something similar.

 

Does anybody know about this? Is it possible that it works this way or maybe there's an opto-laser-electronic principle used? I'm asking because I'd like to have four seperate push-buttons (volume +/- and title >/<) outside the stereo.

 

Here's a pic of the regulator of an actual Retrosound Zuma:

 

RETROSOUND-Poti.thumb.JPG.5978b7b891d69f4e57110b4ff147cce5.JPG

 

What do you think?

 

Thanks in advance,

 

Henning

 

 

Link to comment
Share on other sites

Hi,

 

Most likely, it's an encoder.  An encoder produces a Gray Scale output where two channels pulse in quadrature.  By looking at the pulses and their position, you can determine both direction and number of "clicks".  The most common method is to use a logical XOR.  Encoders are simple, reliable and easy to interface to a microcontroller.

 

I doubt the one you have is optical since those are expensive.  It is probably a simple mechanical encoder.  Nothing wrong with them at all, for the intended use.

Link to comment
Share on other sites

Hi Henning,

 

As to your question about having four separate buttons, unfortunately no, an encoder cannot be replaced by two buttons.  The controller is expecting to see quadrature pulses.  One way to do it is to make a circuit to generate the quadrature pulses on a button push.  Can be done but it is going to be more complicated than wiring up two buttons.

Link to comment
Share on other sites

This...

This...

This is no good start into the Easter weekend. No, it isn't.

 

At first, I nearly tore off the rain gutter trim in the car wash. Then my favourite waitress in the bakery wasn't present. And now I have to read that it is not possible to have volume switches away from the stereo. Really no good start.

 

What I'm wondering: the E46 of a buddy of mine has volume switches in the steering wheel- small push buttons. How do these work since they don't rotate??

 

The gauges are here:

 

The small red button is for releasing the passenger's door. It opens just one or two inches, not entirely. There is also a small circuit to prevent the door from opening while driving but it doesn't work. Unfortunately electronic gurus have died off...

 

hen

 

Link to comment
Share on other sites

Hi,

 

So sorry Hen!

 

I didn't say it was not possible to have pushbuttons, it's just more involved than wiring four buttons in.  Anything is possible - a small microcontroller can be programmed to simulate the pulse train upon a button push.  That's not too difficult to do.

 

Later cars like the e46 use a serial bus arrangement.  All the steering wheel buttons are read by a processor in the wheel which converts each press to a "word".   The word is pushed down one or two wires via slip ring contacts to the main computer which decodes the word and executes the function.  The e46 uses a mix of buses.  There's at least an M-bus, a K-bus and of course, the CAN bus.  There are a few other buses that BMW has come up with so these cars have become very complex.  What's a poor hobbyist to do??

Link to comment
Share on other sites

Thanks a lot, Healey. Even if it's not what I was hoping to learn...

 

So: if I want to have these buttons in the area of the steering column, I would need an additional circuit with a microcontroller? I'm in the wrong business, it seems. And I thought it was such a good idea. Sigh...

 

retriever1.jpg.9811382f8f98838bff46167f2cf9de57.jpg

 

Any euro spec parts you need for your 02, Healey?

 

hen

 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...