null

Hi David,

Interesting question!

Basically make sure you wire things up correctly (don't get power and ground the wrong way round) and when powering something up set the current limit on your power supply to something small (say 100 mA) or just enough to power the circuit.

I would say that most things blow up when you try to shove too much voltage up them.

And the cardinal rule is 'Don't let the magic smoke out!'

null

Hi David,

Forget about the current for the time being, As the IC will have an internal resistance Ohms law will dictate how much current it will draw. Just keep the voltage within the spec for the IC.

The exception to this may be for Op-amps and ICs that drive outputs, for these make sure that the outputs are not driving too much current (the classic error is to connect an output to ground and then try to drive it high).

Also watch out for voltage regulators, they can get very hot if they are dissipating a lot of power. They often need heatsinks to help take the heat away from the silicon.

If your not sure about any mbed related circuits the post a schematic on the forum and ask people for some advice.

Welcome to the wonderful world of electronics!

Martin

Hi,..

as a bit of a noob myself, I'd say I'd discovered it's always volts, it's always volts because current is "drawn".

Had this conversation with someone at work recently, trying to explain the difference, after they were saying that I didn't understand electricity, while I was rewiring my house.

I ended up explaining to them they had a 32A ring main in their house, when they plugged a light bulb into it, that light bulb didn't run at 32A! but how come, if it's a 32A ring main ? Well. it "draws" current. So it's important you get the right voltage, then the component will draw current. It's like the ring main has 32A available to be drawn.

Oh, and Ohms law.. learn ohms law backwards, or you end up writing V=IR and switching it round every time you want to know what current your components will draw ! (I've still not learnt I=V/R, I still only remember V=IR, and switch it round when I need to)

Yes, you can connect your PSU, set at 3.3v to a 3.3v component. The IC will draw as much current as it needs up to the rating of your supply. If you have a 1A supply, it can safely draw 100mA from your supply.

EDIT: By the way, just to prove a point, a dead short is a very low resistance, I=V/R, therefore a very low resitance means a very high current. which is why a short ends with a flash and a bang. It'll try to draw a very large current through things that weren't designed for it. So, if you are driving a digital out high, watchout for what you are "drawing" out of it.

null