voltage regulator +/-

Cato, thank you for the schematic CAD program. I will look it over.

 

Log in or Sign up to hide all adverts.

it's a pretty nice program for a freebie.
i'll probably be going to the website for updates and plug-ins

 

Log in or Sign up to hide all adverts.

i sent him a circuit that will vary the voltage from plus to minus
but i don't see how it could work with your h bridge

i'm thinking he could connect it to a dc coupled audio power amp

when he posts it i believe a lot of solutions will present themselves

 

Log in or Sign up to hide all adverts.

The H bridge design works best if you feed one side the inverse of the other. When one side is at maximum voltage, the other side is at minimum. All you have there is a pair of voltage followers with an op amp to force the output to track exactly the voltage that is applied to the input. I'm still trying to figure out a schematic for that.

The other way is to connect the input of one side to exactly half the supply voltage. This works, but the supply has to be twice the voltage for the same swing.

 

I like the h-bridge idea more (even though I am not familiar with voltage followers and op amps =] )

sorry for not knowing more. I am just getting to the electrical stuff this semester. before it was all like general engineering and math. my whole knowledge of circuits comes from self teaching.

anyway, here is the latest schematic leopold99 sent me:
http://www.killerkittykats.net/quik/cato/schem3.JPG

 

Leopold's schematic is almost there. Both potentiometers need to be hooked to both sides of the power supply. Make sure that one is wired backwards to the other. They should be at the very least 2000 ohms. Almost any value that you can find above that should work. These potentiometers must be linear and physically ganged so that when you turn one dial, you turn both. Then one wiper goes to one input of my schematic, and one to the other. I would much rather that the voltage to the potentiometers be regulated.

You can learn all the things that you need to in a weekend. Get your Ohm's law and the basic principles of transistor operation down.

 

I know ohms law, KVL, KCL, I am ok with nodal analysis (though not great), and I know how diodes/transistors work. I am just not sure what you are talking about sometimes. =]

if I had a bit more free time, I could make a diagram, and organize my thoughts. I could do it tomorrow, but the colts have will be on =]

http://www.killerkittykats.net/quik/cato/out4.gif
where would leo's diagram attach to this diagram. =/

 

The wipers of the potentiometer attach to signal+ and signal-.

 

quick question: where would I get a POT like the one in leo's diagram? do them sell them?

because the reason I was having trouble designing one myself was because I was trying to do it with a classic potentiometer where all you can do is turn up or down the resistance between two leads.

 

you can get the pot at radio shack

they will be mouted on the same shaft

in essence you will turn one knob and vary both resistences at the same time

 

yes metakron is correct
instead of connecting the wipers together as in my schematic
one wiper goes to + sig. to other wiper goes to - sig.

don't forget you need a regulater in there somewhere
if you want a regulated supply

 

right, I will draw my idea later tonight and post it. I have to go to work right now.

I think I finally have it figured out. =]

 

i am not so sure this will work
if you breadboard this circuit expect to burn out your pots

i believe the best course to take is to use my last circuit and connect it to a regulater and from the regulater to a power output stage

the h bridge will not produce zero voltage at the outputs

correct me if i am wrong
you want a supply that can swing from +15 to -15 volts by turning one knob

 

Leopold, 2k of resistance at 30 volts gives you 15 milliamps at 450 milliwatts. I was thinking more like 12 volts for 2k. You really want at least 5k if you are using a 30 volt supply. As long as it is a pair of linear taper potentiometers and their resistance is not so low that they get warm they will work. You won't burn them out. Also, the input impedance of the circuit is high enough that any potentiometer you find will supply enough current. This bridge works really well with about a 12 to 18 volt single-ended supply. You need about an extra 2 volts for the voltage drops of the transistors, but the circuit will track the input voltages exactly within that limit.

It will give you zero whenever the two inputs are at the same voltage. When one side is as high as it will go and the other side is as low as it will go, you get maximum voltage one direction. Reverse this and you get maximum the other direction.

Leopold, you do understand that Cato and I are talking about using your circuit to feed voltage to my circuit, right? My circuit will work with less than a microamp of current to the inputs.

 

I made a first draft of the circuit I had in my mind. it does not have any resistors in it, and may have other errors. but it will show you what I am thinking about.

sorry about the circuit mess, I was designing it as I was drawing it:
http://www.killerkittykats.net/quik/cato/circuit draft 1.JPG
if wires cross without a black dot, then they are not connected.

there will be filters for the DC, and I will correct the voltages, and see if I made any other errors, but it's a start

p.s. I still don't completely understand your circuit, metakron. otherwise I would have used it in this initial design. =]

 

metakron
when the pots are at midpoint the output of your circuit will be at half voltage.
granted the difference between the two will be zero.
i also didn't realize that the pots won't be passing much current

cato
i understand metakrons circuit better than i do yours
you seem to have the base of one of your transisters connected wrong
the lower right hand base should be connected to or with the base of the lower left hand one

 

all of the bases are connected together. if there is a positive voltage coming from the POT, two of the transistors will pass current, completing a circuit through the motor. if the voltage is negative, the other two will pass current. I don't think I have any messed up, but maybe. I will check later.

I think you are right though, metekrons is still probably easier to get. if metakron makes a complete circuit, I would be able to follow along better because I can just trace what the current will do.

 

here is a better look at what I am talking about
http://www.killerkittykats.net/quik/cato/circuit of interest2.JPG

all of the bases are connected together, and will all have either a positive or negative voltage. my transistor knowledge is a bit rusty, but I think it's good.

if I messed something up, let me know. after all, I started this thread because I want to improve my electronics skills.

p.s. if you want the tinycad files to edit, let me know, I will post them.

edit: updated link to newer/ more clear circuit.

 

i used to have a good book on transister circuit design but i can't find it
i moved recently and i bet it got left behind

about your circuit
it seems to be okay. you do realize it won't be as simple as you depicted right?

 

how do you mean?