control resistance x2- from a single slider?

[harps]

hello : )

I wonder if anyone can help? I've been trying to make two little circuits that are able to vary resistance and that can can be controlled from a single slider.

i've made a picture below to aid explanation. ( the orange box things in the picture are the circuits i am stuck on)

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The two circuits vary the resistance of the two channels and work the same but opposite to each other, so when one is high the other is low and when the controller slider is central the two resister circuits are equal.

i have tried lots of things , but i am now thinking to buy a couple of vca ic's and use a transistor not gate type circuit to flip one of the channels over? But so many times people on here think of great solutions, i just had to ask first : )

thanks for any help : )

 

[3v0]

It would help to see the circuit schematic.

If the resistance in both cases are connect to a common point like gnd or the supply voltage you can use a single slider pot. Connect the common point to the wiper and connect each of the circuits to one of the ends. It will do exactly as you requested.

 

[crutschow]

If you need separate isolated circuits you could use a ganged (stereo) pot such as this.

 

[harps]

hello i do not have a schematic as i have failed to make anything as of yet, but maybe i can elaborate ...i took apart a little servo for an RC car ..the servo has a dual potentiometer inside that acts like the two circuits above

clockwise = 0 + 3.6k
central = 1.8k + 1.8k
anticlockwise = 3.6k + 0 ohms

i hope to replace this dual potentiometer with a slider, so the slider controls the servo circuit, and then i connect the servo circuit to the slider as it is a motor type slider. then i can control the motorslider via pwm.

So the problem is that the slider is an 11k linear potentiometer which is nothing like the servos dual potentiometer. So I am trying to convert the 11k slider into a simulation of the servos dual pot. Then the servo will be fooled into thinking it is controlling its own motor on the servo, when really it will be linked up and controlling the sliders motor instead. : P

 

[crutschow]

Unfortunately there is no easy way to convert the voltage from one pot into the linear simulated resistance of two isolated pots. Simple conversion schemes using transistors are not isolated and highly non-linear.

 

[harps]

hows about the slider controls a field-effect transistor that controls a VCA ( which gives variable resistance)? With one of them in a not gate type configuration to flip the one channel? ?

thinks ....oh darn I sense the end of my little design. this is not looking to good. :3