How to self-made a knob to control volume

**Frigor** · 03-07-2005, 02:40 PM

I know there are a lot of rotary knob like PowerMate, but they are too expansive and often too big...

I'd like to embed it in place of the cigar lighter knob

I looked around and found this:
http://www.phidgetsusa.com/viewproduct.asp?SKU=1052

But, how to integrate it in a working system? has anybody done something similar?

Thank you...

**frodobaggins** · 03-07-2005, 03:18 PM

yes they have, seen a few, don't know the links

**jcdillin** · 03-07-2005, 03:26 PM

if I remember correctly someone just modified the scroll wheel from a mouse, I dont know if you want to get that deep into it, and I think they used girder to map the function to volume

**drait** · 03-07-2005, 03:30 PM

http://www.mp3car.com/vbulletin/sear...earchid=751821

There have been a number of posts concerning the use of Phidgets and rotary encoders as volume knobs (and other functions as well). One of the easiest way to obtain a volume knob is with an older scroll wheel mouse that still uses a mechanical (rotary) encoder for the scroll wheel. You remove the one on the PCB and replace it with a higher quality one like the ALPS and use Girder to capture the MWHEELUP and MWHEELDN events. Send those to the system volume and you've got volume control (Girder even has a nice OSD for vol control). You can also capture the mouse click from button 3 (or whichever it is on your mouse) and use it to mute or pause.

**ddn** · 03-07-2005, 03:35 PM

3 Easy Steps:

1. Buy Phidgets rotary encoder.
2. Find and glue knob on.
3. Install in dash.

What is so hard? It says right on the site:

Rotary Encoder. With dedicated USB cable for small form factor applications.

Our encoder is a prepackaged solution needing no other hardware to run. Simply plug into the USB port and go!

16 clicks for the full rotation.

Doesn't get any easier than that.

**rubicon** · 03-07-2005, 04:34 PM

FWIW, I got an optical encoder from Digikey; planning to hook it up to the parallel port of my M10k (since its not doing anything anyhow).

If anyone's interested, I can post pics/schematics/code when I'm done.

**Nic** · 03-08-2005, 06:12 AM

yes please schematics pics and code would be awesome

**rubicon** · 03-08-2005, 10:11 AM

Originally Posted by Nic

yes please schematics pics and code would be awesome

Ok, as soon as I get all the parts and get it (nominally) working, I'll post some info. Should be sometime next week, unless I get the parts in time for the weekend.

**rubicon** · 03-08-2005, 11:47 AM

Alright, so I couldn't wait.

Parts list:

1x Grayhill 61C11-01-08-02 (32-position optical encoder w/switch)
1x Spiffy aluminum knob for the encoder
3x 10kOhm resistors (pull-up; one for each output + switch)
1x PC Parallel port + mating d-sub plug
various connectors, pieces of a CAT-5 cable, solder + burned fingers, etc.

So, I'm using a variant of the circuit shown on the 2nd page of this PDF document.

For +5V, I'll be using a GPO off of my (soon to be had) Matrix Orbital VK204-25 display, since it'll be right next to the encoder.

For the data acquisition, I'll be writing a small C program to (for now) poll the parallel port. Since the encoder almost always has at least one of its outputs high, I don't think an interrupt-driven scheme will work here - would *constant* interrupt servicing be any better than polling?

FYI, most of the daemons I'll be writing for this project will be in perl, with C for the speed-critical stuff.

Circuit diagram + more info to come.

**Frigor** · 03-09-2005, 02:39 AM

Originally Posted by drait

One of the easiest way to obtain a volume knob is with an older scroll wheel mouse that still uses a mechanical (rotary) encoder for the scroll wheel.

Where can I find a mouse like this? I knew that all the mouse wheels were optical...