Has Anyone Tried This Before??

[onform]

Hello

I would like to include an led ring around the volume control, of a valve amp im planning to build, to denote the position of the knob as i dont want markings on the face plate and I was wondering if anyone has done this already on their own build. being a bit of a beginer I am asking for the help of some of you very experienced people on here on how to achieve this.

Any help would be much appreciated.

[onform]

what do you think??

[soundbrigade]

I haven't done it but I have a few ideas.
One is to use a multi-way switch for volume control and use a spare deck for switching the LEDs.
Another could be mechanical, where you have a ring of LEDs, all lit, and a disc with a hole mounted on the potentiometer axel. That will only show one led at a time.
A third is to use a PIC to control a motor potentiometer and at the same time lighting up the leds. As input, you use a rotary encoder.

[onform]

I intend on using a switched attenuator, with an extra wafer. but how would i need to wire it up? and what resistors would i need for these: http://uk.rs-online.com/web/search/s...duct&R=6542601

will i need to make my own curcuit board??

Any help please

[soundbrigade]

Easiest is to have one LED to light up at a time. In that case you wire the LEDs to the various "contacts" on the extra wafer. You hook up a suitable resistor to the wiper. For 6VDC I guess 220-470 Ohms could be OK.
If you want to light up like a scale, well more time is need to find a good solution.

[Karsten Sømand]

Hi onform

My suggestion goes in the same direction as soundbrigade. When using an attenuator with fixed steps it should be easy to mount a single diode to the attenuator.

In this way you have to carefully measure all the steps and then drill holes in the front of the cabinet. Now you only have to mount one single diode to the attenuator shaft so that in each position it is pointing directly to the holes you have drilled. A little piece of flat bended metal should do the trick.

When using this solution you do not have to make any special electrical connections to your attenuator but only needs one single diode with light on all the time.

If I didn´t miss anything here, I really hope you can use my suggestion.

Kind regards

Karsten

[wrenchone]

If you want the LEDs to light up in a row, (1 for min volume, all for max volume), use a constant current source with enough voltage behind it to light all the LEDs in series, plus some to keep the current source alive. Connect the LEDS in series with taps for the rotary switch. Put the current source on the moving contact.

[HollowState]

While this is not exactly what you asked for, it's something I prefer because it's more subtle and easier to do. A single LED with the color of your choice recessed mounted in an aluminum knob. The rear of the knob is relieved enough for the two thin wires to loosely wrap around the shaft. This is an example from the Cayin A-50T.

[CLS]

Use this and a voltage related to the rotation of the knob should get the job done.

[Geek]

Originally posted by CLS
Use this and a voltage related to the rotation of the knob should get the job done.

That's got to be one of the longest production run IC's next to the 741 and 555