Hello, I'm a noob , so I have a question about current. I have a wall charger for a psp console , which is rated at 5v 2000 mA . So, that 2A (2000mA) rating means that the charger is able to supply 2 amps , or that the charger gives 2 amps all the time to anything that is connected to it?

Thanks

Also, is that 5v voltage regulated? Thanks

Is able to supply... Current can only flow when there is a path for it to flow, and the resistance of the path (coupled with the voltage available) determines the current (ohms law).

A supply will have its own current limit above which it struggles (overheats, blows a fuse, gracefully backs off), and that's the rated current.

Whether the voltage is regulated is harder to know - measuring it with no load is a good test.

Thank you very much for helping me MarkT!

Ah, I have one more question ... (Forgot about it) I read somewhere that we cannot use an atx power supply to charge some batteries , because 11A would "cook" them. Is that true? I'm confused , because you said that current flows when there's a path for it to flow. So , will the batteries allow 11A to flow through them ? Thanks

Charging batteries is forcing current into them. To do this you need a bigger voltage than the batteries.
Batterys are non linear devices and do not follow ohms law.

So while you can over charge the battery you only do so if the voltage is such that you can do it. Putting this power supply with a battery will not necessarally put 11Amps through it.
It looks like that writing was badly worded.

Well, about the power supply, I tested it with a multimeter (with no load) and the reading was 5.39 v.
So , is the power supply regulated ?
Thanks

Erm, "no very well" - it should be closer to 5.0V if properly regulated - maybe its not strictly DC too (so I'd not recommend using it as logic power supply without further investigation.

A proper 5V supply for digital electronics should be within 4.75 to 5.25V range (usually better tolerance than this).

maybe its not strictly DC

What do you mean ?

Anyway… I won’t use it as a logic power supply, but will it do as a power supply for a 5v solenoid?
( Also, I forgot to mention that the charger’s + and - have some resistance between them. Is that ok ?)

Thanks

Quote maybe its not strictly DC What do you mean ?

He means it might have ripple on it.

I forgot to mention that the charger's + and - have some resistance between them. Is that ok ?

A resistance reading of a power supply's output has absolutely no significance what so ever.

Arduinoisawesome: Well, about the power supply, I tested it with a multimeter (with no load) and the reading was 5.39 v. So , is the power supply regulated ?

I don't see the value of measuring an open supply to see its output. If it is a switching supply, it may not regulate until there is a load on it. That supply is designed to power a relatively high current device (PSP).

Try loading the supply with a couple of different resistor types. 10k, 1k, 100ohms. See what the voltage is when each of those gives some kind of load to the supply.

I forgot to mention that the charger’s

Is your power supply a charger? If so it needs to be greater than 5V to charge a 5V battery.

If there are charging circuits inside it then it will not be suitable to act as a power supply because it will try and adjust the voltage to keep the current constant.

Grumpy_Mike:

I forgot to mention that the charger's

Is your power supply a charger? If so it needs to be greater than 5V to charge a 5V battery.

I think this is an example of someone mis-using the term "charger." The wall-wart for the PSP is just a 5V supply. The charging circuit is built into the PSP itself.

Thank you all for you replies.

The wall-wart for the PSP is just a 5V supply. The charging circuit is built into the PSP itself.

I think you’re right. I opened up a PSP battery, and there was a circuit board inside, it was the protection circuit(I had to cut a trace in order to hack the PSP) and maybe the charging circuit.

it will try and adjust the voltage to keep the current constant.

So, would a charger like this work for a solenoid?

Try loading the supply with a couple of different resistor types. 10k, 1k, 100ohms. See what the voltage is when each of those gives some kind of load to the supply.

Thanks, I will try that.

A resistance reading of a power supply’s output has absolutely no significance what so ever.

I asked about the resistance , because I thought that there was a short circuit. Is that possible ?

I asked about the resistance , because I thought that there was a short circuit. Is that possible ?

Not and it gives a voltage output. An unpowered electronic circuit just looks like a bunch of diodes so it will look like a very low resistance, but this tells you nothing.

So, would a charger like this work for a solenoid?

No.

Arduinoisawesome:

it will try and adjust the voltage to keep the current constant.

So, would a charger like this work for a solenoid?

Sigh. It is not a charger. It is a power supply. These are very different things. (Consumer goods use the term “charger” now to mean “power supply”. But in reality they are very different circuits.)

Arduinoisawesome:
I asked about the resistance , because I thought that there was a short circuit. Is that possible ?

You can’t measure resistance of active circuits, like a power supply. Trying to measure the + and - terminals of your power supply won’t result in a meaningful result.

Ok , thank you for your replies.