Resistor Load Bank Switch Question

Maybe use relays?

D from BC British Columbia Canada.

What kind of resistors are involved? Too expensive to just implement both arrangements?

A 4PDT will do it:

+----------------------------+ A | | o---+---[R1]---+---------+ | | | | | | [R2] | | | | | | | o o o | / / / +--------o o o o o o | | | +------------------+ | | | | +--------o o | | \\ | | o | | | | | [R3] | | | | o---+---[R4]---+---------------+ B

As drawn, the 4PDT is in the parallel position. A and B are the connections to the "outside world".

If you can't get a 4PDT at a reasonable price, you could use a 4PDT relay or even 2 2PDT relays.

Ed

Could you live with an odd number of resistors? Then you can use a set of single throw switches:

-----+-----------+---------------+ | | | | / / | / / | | | | +---+---+ +---+---+ | | | | | \\ \\ \\ \\ \\ / / / / / \\ \\ \\ \\ \\ / / / / / | | | | | +---+---+ +---+---+ | | | | / / | / / | | | |

---------+---------------+-----------+

Thanks, Alan

Perfect, between both of those I can figure out a good arrangement. How do you guys come up with these? I worked on it for some time and didn't get very far. Thanks for the replies! Steve

There's another one similar to Alan's...I think I can describe it well without resorting to ASCII-art. String (arbitrarily long) of resistors connected in series. At each end, and at each junction between resistors, connect the moveable contact of a SPDT-with-center- off. Wire all the "upper" fixed switch contacts together, to one banana jack, and wire all the "lower" fixed switch contacts together, to another banana jack. Now you can have many possible series- parallel combinations, including all in series (one end switch up, other end switch down, the rest off) or all in parallel (alternating up and down). With 10 R in series, you can go from R/10 to 10*R resistance, with a pretty good range of resistances between.

Cheers, Tom

Nice.

+---R---+---R---+---R---+------}}---R---+ | | | | | | | | | | | o-------o-------o-------o--}}-----------o---0 +---- +---- +---- +---- +---- o-------o-------o-------o--}}-----------o---0

Thanks for all the replies. I actually used a variation on this circuit, instead of spdt switches i used spst switches, two for each resistor, due to the amount i had on hand. Seems to work just fine, and gives me plenty more values instead of just four resistors being switched in parallel.

Thanks again. Steve

Watch out for the ratings of the switches, if you are anticipating hot switching, particularly for DC.

RL