Newbie Rheostat Question

[chinabean]

Hi there,

This may seem like a really simple question to some but here goes:

Diagram of the plan so far:

Power input on the right of the breadboard will +9V and -9V totaling 18VDC.
I want to be able to have variable power into the circuit ranging from 10V to 18V, what kind of rheostat specifications would I need to achieve this?

 

[(*steve*)]

A variable dual power supply is the most correct answer.

Or do you mean you want an additional voltage that varies from 10 to 18V (presumably wrt the -9V rail)?

That's not a schematic by the way.

 

[chinabean]

I plan on using 2 9V batteries in series to create the 18V. I want to be able to reduce the voltage going into the circuit using some kind of a potentiometer/rheostat that will allow me to reduce the voltage to 10V, but also allow me to use any voltage in between 10-18V. Does that make sense?

Forgive my ignorance, I'm a real novice.

 

[(*steve*)]

I assume you still want your power supply to be symmetrical, i.e. you want to vary it from +/-5V to +/- 9V?

It's not trivial to do this.

One way is to have a variable regulator set to between 10 and (say) 16V and then use an op-amp with a power output stage (like an LM380) to provide the 0V rail.

I suspect that will be more effort than the circuit you're testing.

You could use 1.5V cells, starting with 3 on each side (4.5V) and adding 0ne at a time until there are 6 on each side (9V), which will allow you to step up in approx 1.5V steps. But it wouldn't be continuous.