variable voltage source for 0 - 5VDC

Output is from the negative terminal to the wiper of the pot.
The battery is a PP3 9v battery...You can't get much simpler than this.
Del

There are plenty of adjustable voltage regulators where the pot controls the regulated output if you want better stability etc.
You'd need to look at the application notes ... I sugest you check out the National Semiconductors web site and appnotes.
I suggested the initial circuit as the parts are available in any electronics lab.

Del

Hi all, This is Ken. Del, has the person asking for this power supply made any mention of how much current he needs to supply and whether he really needs it to be variable?

Ken

Hi, Ken.

I think you'll have to take RTU to mean "remote terminal unit", which (especially when taken with "0-5V signal") would suggest a fairly high-impedance input device.

I also think you have to take "0-5V signal" and "variable voltage source" to imply that he wants it variable.

Just my take on it,

John

John,

None taken. I appreciated your clarification. Where I work there are THOUSANDS of acronyms, way too many if you ask me, and those three letters just didn't key on any I was familiar with. Seems to me that for the most part, Del has provided pretty much what the guy should have and with your comment that it is most likely a high-Z input device, current isn't going to be much of an issue. The one thing I'm concerned about would be the impedance of the potentiometer wiper arm to ground in parallel with the input of the RTU. Del, does this present any concerns to you regarding your suggested circuit? In any case, I look forward to the requester's reply to all that has been provided.

Ken

Del, does this present any concerns to you regarding your suggested circuit? .

Nah!

Generally the ideal circuit has infinite input imedance and zero output impedance.

The Pot wiper is some where between

.
BUt seriously...I sugested a 1k pot because I thaught it wouldn't be too high an impedance.

Obviously the cct is quick and dirty... but it has the great advantage of simplicity and understandability, ans should do the job, doubtless the pot will get a bit twitchy down the dottom end.

If I was being fussy I'd probably add a small resitor to the bottom end ...depending on what I had lying around... 15ohm.... whatever.

I'm a great believer in the old school 'have a play with it' sort of design.
Del

<...a great believer in the old school 'have a play with it' sort of design...>

Bravo! There's too little of that these days.

I loved Del's comment "I'm a great believer in the old school 'have a play with it' sort of design." as I'm an experimenter also. The design is always a challenge but the design is worthless if it doesn't work under all conditions. Good one, Del.

Ken

John,

Sorry I've been out of the loop for a bit. Have been working on a divorce since 2006 and finally have gotten it completed as of this past Monday. Phew! Anyway...thanks for the help on the RTU and the information about the impedance we're talking about. That wrapped my question quite nicely. Again, thanks.

Ken

Del, Sorry about my last message. Obviously, I hadn't read the first message as I thought I had. Your idea is certainly fine but I think your reference to National Semiconductors Application Notes for the 7805, or better still, the LM317 series which were designed for variable voltages. It seems as though your idea should be dead on since it prevents any output voltage greater than 5-volts but not knowing anything about the RTU (like what is an RTU) I can't comment but it seams as though the LM317 might be better. As Dell has said though, I would definitely recommend looking at the National Semiconductor application notes.

Hope this helps. If not let us know what you still need to know.

Ken