Hello,
I have a DC transformer, from an HO train set, mounted way underneath my train table. I use it to power my DC accessories.
Because it is so far underneath the table, I have to "pre-set" the voltage lever to about the middle range, and leave it there, for all of my accessories to work. The problem is, with this arrangement, the accessories only operate at one speed.
Currently, I have the positive wire running to a simple on-off toggle switch on the side of my table, before going out to the accessories, so that I can turn the accessories on and off. But, I would like to replace this switch with a DC potentiometer, so that I can control the speeds. The negative wire from the transformer currently runs to a distribution block, which has attached to it all of the negative wires running out to the accessories.
My question is, why do these potentiometers have 3 places on their sides, to attach three wires. I know that two of them are for the "in" and "out" of the power wire, but what is supposed to be attached to the third one? Is it a ground? If so, why would this rig need a ground?
Is it for the "negative" wire from the transformer to attach to? Before the negative wire goes out to the distribution block?
Thanks very much for any info.
Mannyrock