Quick help with electrical problem

Edit:
Look below to post 5.

I think you need something like a basic op-amp:
http://ourworld.compuserve.com/homepages/Bill_Bowden/opamp.htm

Looks promising but isn't that for a AC system or can one be built for a DC system? I'll look into it. Thanks man.

postaldudeleo said:

Looks promising but isn't that for a AC system or can one be built for a DC system? I'll look into it. Thanks man.

Click to expand...

You can build one for a DC system. It amplifies whatever signal you give it. It this case, your signal isn't something like a sine wave, it's a roughly constant voltage.

I agree with Gnufsh I think a basic op-amp would do you fine.

Nope tried a few things didn't work like I hoped. I think I might need something else.

Is there anything that you can buy that can do this.

I know exactly what I need now.

Or simply put, I need a component (a special resistor?) that has two wires passing clear through it. As power on wire 1 decreases, the resistance that wire 2 must cross increases. As the power on wire 1 increases, the resistance on wire 2 decreases (from a fixed middle resistance.) I think that such a simple thing has to be common but don't know what it's called.

postaldudeleo said:

Nope tried a few things didn't work like I hoped. I think I might need something else.

Is there anything that you can buy that can do this.

I know exactly what I need now.

Or simply put, I need a component (a special resistor?) that has two wires passing clear through it. As power on wire 1 decreases, the resistance that wire 2 must cross increases. As the power on wire 1 increases, the resistance on wire 2 decreases (from a fixed middle resistance.) I think that such a simple thing has to be common but don't know what it's called.

Click to expand...

Seriously, it's called an op-amp. That's what it does (among many other uses). You probably want to setup up something like a low-gain (or no gain) amplifier.

Can I buy these things fully assembled at radio shack or etc?

I can't seem to think of a way to get this to work with two wires which use seperate power sources. Can I just solder a wire to each endpoint with wire 1 to solder point 1 being wire a, wire 1 from solder point 1 being b, wire 2 to solder point 2 being c, and wire 2 from solder point 2 being d?

postaldudeleo said:

Can I buy these things fully assembled at radio shack or etc?

Click to expand...

Yes.

I can't seem to think of a way to get this to work with two wires which use seperate power sources. Can I just solder a wire to each endpoint with wire 1 to solder point 1 being wire a, wire 1 from solder point 1 being b, wire 2 to solder point 2 being c, and wire 2 from solder point 2 being d?

Click to expand...

You lost me here.

I drew up a pretty simple thing in paint.

Basically I need something that if amp or volts on wire 1 changes then amps or volts on wire 2 changes respectively. Both wires must pass through the thing (it would fit in the middle of both wires) instead of joining there and thats the main problem.

Well, since you deleted your first post I'm not sure what you want to do exactly but here's what I think you want.

If you want the voltage or current off of one wire to control the current passing through a second wire, then that is exactly what a transistor (MOSFET or something similiar) does.

I'd need to know the application to recommend a part, but from what the picture shows it seems that's what you're looking for.

What application???
You probably want a voltage controlled voltage source. Depending on the power requirement, that can be done with one or two (properly sized) transistors. There are high quality and protected controlled sources but I think you don't want to pay 800$ for them If you build one, you must understand the basics about transistors. We are talking about linear electronics here, so depending on your background, that could take quite some time.

You could also use an op amp with anoutput transistors, because op amps can't put out any decent current; make sure you don't overcharge it because you will end up with a blackened or cracked chip AH, the odour of electronics... Good luck!

Just what is it you are trying to do? Post 5 below this is about modded heatsinks

More or less, this for a controller. The current on wire two is being controlled by the current running from wire 1 which runs from the controller itself. The controller was fairly simple except for this part. This is one of the outputs of the controller.

I was thinking of transistors but I knew that transistors had only 3 wires while I had 4.

Here are the spec.

The specs.

Wire 1= up to 1 Watt

Wire two= up to 1 kilowatt so maybe a large coil is needed?

and for a second type

Wire 1= Up to 1 Watt

Wire 2= 9 volts, maybe 10 amps

The controller is pretty simple but with a large quantity of photodetectors as inputs, and this gate controllering the output with a few switches and a port to recieve instructions form a computer.

postaldudeleo said:

More or less, this for a controller. The current on wire two is being controlled by the current running from wire 1 which runs from the controller itself. The controller was fairly simple except for this part. This is one of the outputs of the controller.

I was thinking of transistors but I knew that transistors had only 3 wires while I had 4.

Here are the spec.

The specs.

Wire 1= up to 1 Watt

Wire two= up to 1 kilowatt so maybe a large coil is needed?

and for a second type

Wire 1= Up to 1 Watt

Wire 2= 9 volts, maybe 10 amps

The controller is pretty simple but with a large quantity of photodetectors as inputs, and this gate controllering the output with a few switches and a port to recieve instructions form a computer.

Click to expand...

Let me try to rephrase it to understand what you are trying to do. You want to use an existing wire that comes out of a fan voltage controller to control the voltage out of the controller that you want to build. The controller that you want to build takes its power from a power supply, possibly the same power supply on which is plugged the existing fan voltage controller. Is that right?

Second, beware if you speak about current source. I would not think a current source is useful for a fan. In a current source, the voltage can be anything, as long as the output current of the source is at the desired value. It would be hard to determine the exact current needed by a fan to maintain a certain speed and it would start very slowly, if at all, because the motor needs way more current than its steady state current to start. The voltage source is better suited. In a voltage source, the current is adjusted to keep the desired voltage at the output of the source; I mean, the source will give whatever (up to its limit) current needed while maintaining proper voltage. I think that's what you should do.

Now, sure, the transistor has 3 branches. But you must build a circuit that will have all the needed ports. You must first learn how to polarize a transistor. Well you have 2 options here. First one would be to find a schematic that does what you need and do it exactly as shown. Could be difficult, because when there will be a problem, you could not know where it comes from. Second solution would be to start to learn about basics of transistors, without staying long in the physics of the principles. Just the behavior of the different polarizations, like common emitter, common collector... You certainly need an output transistor for your needed output current. For the input where the controlling voltage enters, I think you could use a comparator (specialized op amp chip) and a simple voltage divisor (done with two resistances.) Your output transistor absolutely needs to be polarized correctly. I think the common collector polarization should work fine for it. Do not use the output of the chip on fans because I swear it will die. I don't have much time right now because I'm finishing my doctorate in electrical engineering right now (presentation the 16th of December) but I could come back at you later with a schematic if you are patient.

This isn't exactly a fan controller.....

This controller is to be used for basically a way I want to try to transmit data and build a test program around that.

Thanks for your offer for a schematic. If by that time I haven't figured it out, and you have the free time then that would be great. I am currently reading two books on electronics but not very far into them as it seems.

Anyway, I'll try to explain the basic idea again. There is a gate that is on a spring. To keep open and allow the cars to come through, it needs people to pull
the doors open and hold them there. More people, the more the doors open, and thus the more cars.
Basically the cars are the kilowatt wire and the people are the one watt wire.

To simplify the problem, consider that there are two seperate power supplies, one that goes up to 1 watt, another that goes up to 1 kilowatt. One supples people one supples cars respectivley.

What I want to find out is how to make such a springed gate.
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I must really be bad at explaining stuff if what I'm saying is confusing

I got it! Yay. Party