Can I use 2A power supply for component testing

I was thinking of picking up a power supply to test components. Simple stuff like make sure a LED turns on. Here is an example (Power Supply)

Knowing the Arduino has a max 40mA output, what happens if I test an LED and resistor with 5V@2A?

You calculate the series resistor based on the supplied voltage and the forward voltage and allowed current (or less, most are quite bright even at very low current) of the led in question, and then your circuit only draws the current the resistor allows.

The supply does not impose 2A on the circuit; the circuit draws from that "pool" so to speak.

You could even use a AAA battery for that.

That sounds like a reasonable power supply, though the details are pretty pauce. You are implying a common "newbie" misunderstanding of specifications.

This power supply has an adjustable output of up to 15V and a maximum current rating of 2A. If nothing is connected, no current will flow. If you connect something to it, current will flow according the the resistance of that appliance, and presumably, the power supply will restrict the current to 2 Amps if the resistance is too low. Or it may not, unfortunately the description fails to specify this just as it fails to supply other information that most of us would want to know about it.

Nevertheless, for simple experiments, it is quite useful, just like one (or two, actually) with virtually the same specification I myself built over 40 years ago.

What you absolutely must have even before the power supply, is a multimeter. A $5 one is a good start.

Hi, by the looks of the specs, it is a simple LM317 variable regulator type supply.

The 2A spec looks as if is a proper current limit, not just a specification for max regulated output. However it is fixed at 2A.

The ideal power supply, and unfortunately they are somewhat expensive, is one that has a front panel current limit control.

Tom...... :slight_smile:
PS At that price and free postage, I'd buy one for the case and parts. Then get in and modify.

TomGeorge:
Hi, by the looks of the specs, it is a simple LM317 variable regulator type supply.

Or an LM723 plus 2N3055, as mine were.

TomGeorge:
The ideal power supply, and unfortunately they are somewhat expensive, is one that has a front panel current limit control.

With the slight risk that the current control potentiometer(s) can be dicky or “noisy” and not work reliably. Same for the voltage control potentiometer(s).

TomGeorge:
At that price and free postage, I’d buy one for the case and parts.

Or to take up tattooing?

Thanks for all the information. I am just spinning up my first project and this is very helpful.

@Paul__B - I have a multimeter that is unfortunately out for warranty repairs atm. Also, I know a couple tattoo artists. If I can get a good deal, are tattoo machines more reliable/configurable power supplies for the money?

The ideal power supply, and unfortunately they are somewhat expensive, is one that has a front panel current limit control.

True, but if you can't afford the this:

Variable voltage, adjustable current Lab Bench Supply

You can build your own using an LM317 and a 2N2955 power transistor:

Boosting LM-317 current-DIY PS schematic

(SEE schematic jpg in REPLY #6)

That small bench supply is good for testing with, there is no current limiting, but I think that's a good thing... (you'll only blow a couple of things before you learn :slight_smile: )

Regarding the bench supply, 15amp ammeter do they all come so highly uncalibrated!

Do you mean that picture Paul__B posted ?
In that case have another real close look.

No not Pauls link, the OP’s link to amazon…

Look closely where the needle is, it’s highly uncalibrated, I’m hoping the screw was adjusted for the photo

Ah, the 15 Amp ammeter that shows 15 volts in some pictures, and 11 volts in another picture, that's the one you mean !

Actually, it IS calibrated. if you download the images and zoom it , you'll see the black knob has an em-
bossed triangle on it and the knob setting is lower for the 11V photo than it is for the 15 V photo. My guess
is they moved the knob so people wouldn't think that the only voltage available is 15V, or for some other
reason. You can just barely see the tip of the triangle in the 11V photo (about 2mm wide) just past the
midpoint of the dial. In the 15V photo you can see the shape of the triangle on the right edge of it. The
dial is pointing toward the end of the scale.

PhoenixRion:
I have a multimeter that is unfortunately out for warranty repairs atm.

Spend $5 and get another one. Even better, spend $10 and get two to make sure. I have them lying all over the place (like reading glasses) - home and work - just so I can find one when I need it.

PhoenixRion:
Also, I know a couple tattoo artists. If I can get a good deal, are tattoo machines more reliable/configurable power supplies for the money?

Chuckle. :smiley: What you cited is a dirt common power supply which happens to find a different market with tattoo artists.