How do I know if a servo motor is powerful enough?

[alfa147x]

I'm trying to build a gain controller for my car and I need something to turn a knob on my amplifier. The knob looks like one of these FREQ knobs: Link

I'm thinking a servo motor + my arduino is perfect. Couple of questions:
How do I know which motor is right? Things like power or how small increments I can make.

How long can a PWM cable run?


Thanks!
Alfa

Edit:
I found this:

Motor Type : coreless motor
Gear Type : All Nylon Gear
Dead Band Width : 2 usec
Connector Wire Length : 150mm
Stall Torque : 1.5kg/cm at 4.8V
Operation Voltage : 3.0 - 7.2Volts
Dimension : 22mm x 12mm x 29mm
Connector Wire Length : 150mm
Operating Speed : 0.12sec / 60 degrees (4.8V no load)
Temperature Range : -30 to +60 Degree C

I'll be running it at 5V
It costs $3 I might try it out

 

[MovingTarget]

Trial and error? Sigh, I'm not an engineer. This really isn't my field.

Paging Rubycon...

 

[alfa147x]

Trial and error? Sigh, I'm not an engineer. This really isn't my field.

Paging Rubycon...

That would be nice. Only if I had an unlimited budget

 

[PottedMeat]

you really shouldn't need much torque to turn a potentiometer knob like that.

seems like a complex solution - i guess i'd consider moving the amp or even desoldering & moving the potentiometer to the dash or whatever. if there wasn't any noise i'd be ok with that.

 

[alfa147x]

you really shouldn't need much torque to turn a potentiometer knob like that.

seems like a complex solution - i guess i'd consider moving the amp or even desoldering & moving the potentiometer to the dash or whatever. if there wasn't any noise i'd be ok with that.

I thought of moving the amp but what I want to be able to do is make 5 buttons on a small box that goes near the steering wheel. The five buttons will be
Hip Hop / dance / techno
Rock
Off
Up
Down

This way I have 3 presets and up and down to micro control the gain

 

[PottedMeat]

I thought of moving the amp but what I want to be able to do is make 5 buttons on a small box that goes near the steering wheel. The five buttons will be
Hip Hop / dance / techno
Rock
Off
Up
Down

This way I have 3 presets and up and down to micro control the gain

ah that makes sense. how far apart are the amp & button box going to be?

 

[alfa147x]

ah that makes sense. how far apart are the amp & button box going to be?

5 - 8 feet max

 

[MotF Bane]

This seems like a crude way to go about it. Not that I really know what it is, but it feels like there's a better answer.

 

[alfa147x]

This seems like a crude way to go about it. Not that I really know what it is, but it feels like there's a better answer.

The only other way I can think about doing it is by taking apart the amp. I don't really want to do that :\

 

[The Boston Dangler]

nothing personal alfa, but i think this approach might be pretty problematic. if the servo gets twitchy, that could be bad news. what about using a pre-amp? you could still control it with a custom box

 

[alfa147x]

nothing personal alfa, but i think this approach might be pretty problematic. if the servo gets twitchy, that could be bad news. what about using a pre-amp? you could still control it with a custom box

Hey I'm open to any ideas

I'll look into pre-amps. I don't really want to spend too much money. If it's worth while I can wait and save up for it

 

[The Boston Dangler]

are you using a stock head unit?

 

[alfa147x]

are you using a stock head unit?

Yes. I really hate how aftermarket head units look.

 

[Rubycon]

I don't do car/home audio but going by that amp pictured most of those are mounted in trunks and their pots are usually adjusted once by the installer. Sometimes the owner may move them once in a blue moon. The point is generally those are not pots designed to be moved on a daily basis like a mixer or stage processor would have. This could lead to trouble down a short road.

For your application you would be best be suited with a signal processor inline before your amp. This would give the ability to modify gain structure on the fly including equalization, special processing (for example a subharmonic synthesizer), etc. Done properly this can be controlled anywhere in the car, remote control or even a smart phone app! Done properly it would be inaudible distortion wise.

 

[The Boston Dangler]

agreed, the gain pots on the amps should be tuned to the sweet spot for gain/distortion and never touched again. it's not a volume knob. what would fit the bill is an eq/processor that takes the speaker level input and can be wired for external commands. for that money, i'd rather upgrade the radio and have simplest, most effective system.

 

[alfa147x]

Good info. Thanks guys!