can any one tell me how to control large current using micro processor?

Question

is it possible to control large current using micro processor if so how it should be connected to the current circuit

Answer 1

Sure, almost anything is possible if you put enough effort and money into it. The key questions for you are: How large of a current do you want to control? What kind of load will be connected to that source of current? The answers to the these questions will determine what kind of design is best for your purposes.

There are a variety of ways to solve this problem. Essentially, it is a problem of amplification. The microprocessor can switch a small current by itself. (probably less than 20 mA) You want to amplify that small switching effect, so that it can switch a bigger current.

Two basic approaches:
1. Use a network of transistors to switch the load.

In the simplest case, this could be just one transistor, with its base connected to the microprocessor output, its emitter to ground and its collector connected to the load. (The other terminal of the load goes back to the power source.)

In a more complex case, you may need a chain of transistors connected together to achieve the needed amplification in several steps. If you want to control an AC current, then the semiconductor solution will get much more complicated. It still can be done, however.

2. Use an electromechanical relay to switch the load. Relays are relatively cheap, and they can switch either AC or DC circuits.

Here you would use transistors to amplify the microprocessor's output enough so that it can drive the coils of the relay. Then the relay switches the current that passes through the load. This arrangement has the added benefit that the load is electrically isolated from the microprocessor. That can be important if the load is noisy, or inductive, or involves high voltages.