How can I get 2 amperes?

Question

I need 2 amperes for a circuit, but I can't decide how to get it. Voltage doesn't really matter. Should I try stepping down wall current? I want this to be as cost efficient as possible. Any ideas?

oh, and I would like to be able to change the current from between like 1.5 amps and 2.3 amps if that is possible.

Answer 1

The old fashioned way to source nearly constant current was to put a limiting resistor with a high voltage source. You are talking using a wall outlet so consider this to be AC. The problem is 2 amps is a lot of current. the limit resistor will have to absorb 110 volts x 2 amps or 220 watts. Thats a lot of heat. another way to do this is with a 200 watt light bulb in series with the load, this gives slightly better regulation because if the load draws more current, the filament heats up making its resistance go up, thus bucking the over all change. In the 1920s special light bulb like tubes were made for regulating current called ballast tubes. Also radios of that era sometimes had the limiting resistance built into the power cord to get the heat away from the appliance and distributed over more distance. That was the reason they said never run a cord under the rug, because it could heat enough to cause a fire. The best solution is to go heat free and size the voltage going to the device to the proper level to get the 2 amp draw using a transformer. Adjustable transformers that handle 2 amps of load are not particularly expensive.

Answer 2

Sounds like you need a current regulated power supply. There are very few applications were current is specified and voltage is irrelevant. Usually voltage is held constant and the current varies with the load. It is possible to hold the current constant and let the voltage vary with the load. This is seldom done because uncontrolled voltages will instantly destroy semiconductors. There are, of course, numerous exceptions to the rule.

There are four interrelated parameters, voltage, current, resistance, and power. It is completely impossible to give a more detailed rational response to your question, knowing only one of the principle parameters.

Are you doing DNA sequencing, using gel or paper electrophoresis?

Answer 3

I = E/R so 2 = E/R. Put in your value for voltage (E) and figure out the resistance to get 2A

Answer 4

What you use will depend on whether you need DC or AC and what voltage you need. Even though you say you don't care what voltage it is, in reality, you do.