Motorizing an attenuator

Prune · 12th June 2004, 07:35 AM

I'm planning to use one of the 23/24 position C7 series Electroswitch from Digikey for volume control. However, I want to motorize it so I can hook it up to the remote control receiver. The remote decoder IC outputs pulses, so I need some help figuring out how to turn the attenuator a step each pulse. Any suggestions how to do this?

Tim__x · 12th June 2004, 08:21 PM

It might be easiest to use a small servo and a pic or other similar microcontroller to turn the attenuator.

Prune · 19th June 2004, 10:12 AM

I found a small motor/reduction gear assembly that has enough torque and low enough speed. But how do I disengage the motorization when I'm doing manual rotation of the knob? (obviouisly the reduction gear would not allow me to rotate the knob with any reasonable force).

Tim__x · 19th June 2004, 04:09 PM

If you make the motor driver outputs float (as opposed to grounding both) it shouldn't be too hard to turn by hand. If it still is too hard to turn I would suggest you find a different motor assembly.

markp · 19th June 2004, 05:39 PM

All Electronics sells a motorized dual pot for about $6. It is a dual 20k linear Alps pot. Maybe you could change out the pot elements for log units.

mike galusha · 18th July 2004, 02:06 PM

Quote:

Originally posted by markp
All Electronics sells a motorized dual pot for about $6. It is a dual 20k linear Alps pot. Maybe you could change out the pot elements for log units.

I did something similar. Picked up one of the Alpha motorized pots from Mouser or Digikey (can't remember which) and replaced the pots with a TKD unit. It came out pretty well and looks almost like it was born that way.

The only tricky bit was drilling the holes in the center of the shafts so I could join them. This would have been easy if I had a lathe but careful centering in the drill press resulted in suitable accuracy.

Prune · 18th July 2004, 04:23 PM

The pot motor hasn't got nearly enough torque to move the large switch I have. I used a larger motor with a gearbox that results in about 10-12 rpm at 8V. Couldn't find a driver IC locally, so I built a discrete H-bridge with BJTs driving MOSFETs. Probably overkill, since it managed to drive a garage door opener motor

I didn't drill anything to connect them, just used a short bit of soft plastic tube (the same way I saw the motor was connected to the working end of my rotary tool).

Prune · 15th September 2004, 06:12 AM

The result:

Bill Fitzpatrick · 15th September 2004, 06:22 AM

Could some explain to me the point of a remote volume control?

Prune · 15th September 2004, 06:34 AM

Are you serious?

Most commercial gear has remote controls. It's not just the volume control, the whole DAC can be controlled remotely, power on/off, input selection, output selection... The point is the same as for any remote control -- so you don't have to get up and go to the equipment to change something. If a TV should have remote control, why wouldn't some other piece of A/V eqiupment?

12th June 2004, 07:35 AM	#1
Prune Account Disabled Join Date: Mar 2003 Location: Vancouver	Motorizing an attenuator I'm planning to use one of the 23/24 position C7 series Electroswitch from Digikey for volume control. However, I want to motorize it so I can hook it up to the remote control receiver. The remote decoder IC outputs pulses, so I need some help figuring out how to turn the attenuator a step each pulse. Any suggestions how to do this?

19th June 2004, 05:39 PM	#5
markp diyAudio Member Join Date: Oct 2003 Location: L.A., CA	All Electronics sells a motorized dual pot for about $6. It is a dual 20k linear Alps pot. Maybe you could change out the pot elements for log units. __________________ If it sounds good... it is good!

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12th June 2004, 08:21 PM	#2
Tim__x diyAudio Member Join Date: Jun 2004 Location: Edmonton area, Alberta	It might be easiest to use a small servo and a pic or other similar microcontroller to turn the attenuator.

19th June 2004, 10:12 AM	#3
Prune Account Disabled Join Date: Mar 2003 Location: Vancouver	I found a small motor/reduction gear assembly that has enough torque and low enough speed. But how do I disengage the motorization when I'm doing manual rotation of the knob? (obviouisly the reduction gear would not allow me to rotate the knob with any reasonable force).

19th June 2004, 04:09 PM	#4
Tim__x diyAudio Member Join Date: Jun 2004 Location: Edmonton area, Alberta	If you make the motor driver outputs float (as opposed to grounding both) it shouldn't be too hard to turn by hand. If it still is too hard to turn I would suggest you find a different motor assembly.

18th July 2004, 04:23 PM	#7
Prune Account Disabled Join Date: Mar 2003 Location: Vancouver	The pot motor hasn't got nearly enough torque to move the large switch I have. I used a larger motor with a gearbox that results in about 10-12 rpm at 8V. Couldn't find a driver IC locally, so I built a discrete H-bridge with BJTs driving MOSFETs. Probably overkill, since it managed to drive a garage door opener motor I didn't drill anything to connect them, just used a short bit of soft plastic tube (the same way I saw the motor was connected to the working end of my rotary tool).

15th September 2004, 06:12 AM	#8
Prune Account Disabled Join Date: Mar 2003 Location: Vancouver	The result:

15th September 2004, 06:22 AM	#9
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	Could some explain to me the point of a remote volume control?

15th September 2004, 06:34 AM	#10
Prune Account Disabled Join Date: Mar 2003 Location: Vancouver	Are you serious? Most commercial gear has remote controls. It's not just the volume control, the whole DAC can be controlled remotely, power on/off, input selection, output selection... The point is the same as for any remote control -- so you don't have to get up and go to the equipment to change something. If a TV should have remote control, why wouldn't some other piece of A/V eqiupment?

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