Hi guys,

I've got a resistor ladder in place that can not be removed. I'd prefer not to have to make fancy modifications, either. The circuitry is simple. If the ladder sees, say, 1k across the ladder, a function is performed. Works like a champ with pushbuttons.

I'd like to do the same with a rotary knob if possible for faster action. so that quickly rotating a knob will "basically pulse" a 1k passive resistance across the ladder. Rotation in the opposite direction would do the same, at a different resistance for a different function.

I don't think rotary encoders are set up to do this. I really want to avoid doing something voltage driven. If there is a mechanical rotary knob that will enable this function, it will save me an enormous amount of energy and effort.

Are you guys aware of any products like this?

Thanks,

Steve

 

Why don't you use something like an octal or hex thumbwheel switch?
If you need more than 3 or 4 bits resolution, just stack them.

Here's a hex thumbwheel at Digikey:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CKN5038-ND

If you really want a rotary, they have a couple of those in inventory, but they are a non-stocked item:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=450-1184-ND

Mouser has some PCB mount that are a lot less:
http://www.mouser.com/Electromechan...-vyke?P=1yzvr7m&Keyword=rotary+switch&FS=True
You'd need a screwdriver to actuate them.

Here's another possibility:
http://www.mouser.com/ProductDetail...=sGAEpiMZZMsfGXvUAbE5P3qjwUTwvxOfiomJ3FVio9U=

Check out this Mouser catalog page:
http://www.mouser.com/catalog/catalogUSD/641/1685.pdf
PT65303 or PT36103 might work out for you.

 

Two issues that I might not understand clearly:

Is there a way to change the resistance measured depending on the direction spun?

Most important though, wouldn't this solution mean that the switch would apply a resistance to the ladder at rest, and be open for a brief moment between a position change? The way this ladder works, the switches short through a resistance when depressed. So I would need the opposite behavior through a rotary. The action of rotating the switch would briefly apply the resistance across the ladder.

 

You would need some extra circuitry, but it is possible.

An encoder usually gives quadrature pulses out, so both lines pulse for either direction.

You would need some simple logic to decode the direction and pulse one transistor or the other and simulate the two direction buttons.

 

OK then, why not a simple break-before-make rotary switch of an arbitrary number of positions, leaving both ends open?

Whatever resistance you want, just connect it in series with the common. Connect all of the individual poles together.

 

I believe the idea is that turning the control knob will repeatedly 'press' the Up or Down 'button' input to simulate rotary volume or tuning etc.