9v to 6v????

[nero1985]

can i use a 100k trim to turn 9v to 6v?

[Marcos - Munky]

I believe yes, but I'm not sure about the value that you will need to do this. Also, you can get 4.5V using a V1/2 network (that one with two resistors and a eletrolytic cap) if 4.5V is enought to drive your circuit.

[Arn C.]

I may be too quick on jumping on this, because someone else may have a better suggestion.

Are you using an adapter or battery?

Also, I am not sure how much current trimmers can handle.   I would assume not too much.
First measure the voltage from your power supply to see what voltage it is actually outputting.(write this down for later)

At any rate, you can take one of your leads whether pos or neg, depending on what you will be using in your circuit for power.

Hook your trimmer inline with that lead and connect both the lead outputs to your meter to check your voltage.

If you are using a wall wort power supply, and you know it is  a 9 volt one, your measurement before using the trimmer may give you a reading of (say for example 12 volts dc).

Using proportions  9/12 = 6/x ,  x=8volts(this is what you would set your trimmer to:remember this is just an example voltage)

 Once you have the correct voltage, measure the trimmer to find out what the resistance is and use that value of resistor inline with your power source.  I would use a higher watt rated resistor.  Not sure what value, maybe 1/2 watt or even 1watt to be safe. (Maybe even a 2 watt resistor?)


Peace!
Arn C.

[Thomas P.]

sure you can. Imagine having 9V over pin 1 and 3. If you adjust the wiper to 50k, what do you think it will be? Right, 4.5V.
You must see the pot as two resistors in series. All other things can be done by Ohms Law, which is R = U/I.

[Ge_Whiz]

Yes, but if you use a 100k trimmer the available current will be less than 0.1mA. Will that be enough for your purpose?

[smoguzbenjamin]

You can use fixed resistors in a 1:2 ratio. Anyway doesn't a non-equal resistor splitter fluctuate with current-draw changes? Why not use a regulator to regulate 9v down to 6?

[petemoore]

Have to brush up on the specs but doens' t a LM317 Voltage Regular take 9 down to 6v without getting hot or needing a heat sink? Then you can adjust it...
 What about using two seriesed R's to divide, and rate the current to their values...higher R value means less current [right?].
 So you could use two small ones, like 12k, and some bigger ones like 120k, or [      ]  then adjust one side of the seriesed pair [or the other] value to get the voltage your looking for?
 Isn't a 100k pot how that one mod for New Clipper sets bias...adjustable with the pot?...IIRC there were also 22k's or something on both outside potlugs.
 I know the LM317 works, whether it gets hot for your application I don't know.
 I'm pretty sure you could devise a voltage divider using fixed R's, if it's running an audio amp I'd use a bypass cap or two. I've never done it so this is a question...can't you measure current by splicing the DMM in there to read how much current is flowing?

[stm]

Depending on power consumption, you can use a 3.3V zener in series to drop the 9V to 5.7V, or a 6.2V shunt zener.

[Nasse]

78L06 works ok too

Trimmers and pots smell funny when you put some current trough them

[Hal]

Have to brush up on the specs but doens' t a LM317 Voltage Regular take 9 down to 6v without getting hot or needing a heat sink? Then you can adjust it...
 What about using two seriesed R's to divide, and rate the current to their values...higher R value means less current [right?].
 So you could use two small ones, like 12k, and some bigger ones like 120k, or [      ]  then adjust one side of the seriesed pair [or the other] value to get the voltage your looking for?
 Isn't a 100k pot how that one mod for New Clipper sets bias...adjustable with the pot?...IIRC there were also 22k's or something on both outside potlugs.
 I know the LM317 works, whether it gets hot for your application I don't know.
 I'm pretty sure you could devise a voltage divider using fixed R's, if it's running an audio amp I'd use a bypass cap or two. I've never done it so this is a question...can't you measure current by splicing the DMM in there to read how much current is flowing?

I just made a variable power supply with one of these.  The heat dissipated depends on the current...I'm pretty sure the LM317 simply "drops" the excess voltage, so power dissipated = VI.  I agree, this is probably the best/simplest way to achieve a variable voltage - better than a trimpot as a voltage divider.  I was kinda scared about it overheating, so i clipped a 3w heat sink on, but i dont even think that was nessecary with the low currents i'm going to use.  

Radio Shack has the Lm317's for $2.30, with design help on the back of the package....they also have heatsinks, although i didn't get one from them - i ripped it off something.

[niftydog]

Yes, but if you use a 100k trimmer the available current will be less than 0.1mA

Not quite. The available current will depend on the resistance from the input terminal to the wiper terminal. The voltage will ALSO depend on the current being drawn. They work best when there's a fixed, known current draw.

0.1mA will be constantly flowing regardless of the wiper position. So even if you have nothing connected to the wiper pin, there is still current flowing (read; energy being wasted)

By far the best solution is to use an LM317.

I know the LM317 works, whether it gets hot for your application I don't know.

If an LM317 gets hot doing the job, then a trimmer pot is simply going to melt!!

[Steben]

Depending on power consumption, you can use a 3.3V zener in series to drop the 9V to 5.7V, or a 6.2V shunt zener.

Yes a zener will be better and will not let the voltage fluctuate with current draw in the circuit.

[Paul Perry (Frostwave)]

Is your 9v a 'real' 9v from a wart or similar, or is it a battery?
Because if it is a 9v battery, as it gets flat (say to 7.5 v) then there won't be enough 'headtroom' to operate the regulator properly.
If anyone knows a low-dropout adjustable reg, let me know! (rather than try to kludge with a fixed reg).

[niftydog]

Paul, seen the Maxim MAX603 and similar?

[Paul Perry (Frostwave)]

Paul, seen the Maxim MAX603 and similar?

..much appreciated! I can't keep up with Maxim any more!