[sdiy] A little OT, Begging a hand

[Ian Fritz]

Veronica --

Just an outline of a possible approach.  First combine R5 + R7 = Rx. Then 
R2, R4, Rx, form a delta that can be transformed to a wye, Ra, Rb, 
Rc.  Then you can add together R1 + Ra and R3 + Rb and Rc + R6. This leaves 
you four resistors and two nodes, which you should be able to get.

GL

Ian


At 11:50 PM 2/7/2011, Veronica Merryfield wrote:
>I wonder if anyone might be able to help me out on what I was hoping was a 
>simple problem.
>
>I have the following resistor network (ascii art follows so you'll need a 
>fixed pitch font selected)
>
>  V1
>  |
>  \
>  / R1
>  \
>  /
>  |    R4        R6
>  |--/\/\/\----/\/\/\----- Vout
>  |          |         |
>  \          \         \
>  / R2       / R7      / R8
>  \          \         \
>  /          /         /
>  |    R5    |         |
>  |--/\/\/\--          |
>  |                    V3
>  \
>  / R3
>  \
>  /
>  |
>  V2
>
>I can set each of V1, V2 and V3 to either +Ve, GND or OC independently, 
>although not all combinations are useful, and I can measure Vout. 
>R1+R2+R3=K, about 600 ohms. R1=R6 and R2=R7, R4 and R5 vary between about 
>1K and 500K and R8 is fixed at 2K2 although this can be changed.
>
>I want to set a number of input combinations and measure Vout from each in 
>the hope that I can determine R1, R2, R3, R4 and R5 with some simultaneous 
>equations.
>
>My attempts have been a bit of a failure and I think I am missing 
>something so I was hoping someone here might be able to help me.
>
>For reference, this is the equivalent circuit for a sensor I am working 
>with on a music controller project.
>
>Veronica
>
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