Regulated 12VDC 5A output power supply?

[shaneshane1]

Im buying my first wall power supply tomorrow, regulated 12V 5A, and just want to know how dangerous it could be as i dont really understand the risks in using a transformer, im use to using AA and 9V batteries

eg: will i get electrocuted touching the +V and 0V with my hands

im assuming the answer will be no, but im just making sure

and my next question is really stupid, and i wouldnt even think of doing this, but if i was to touch +V and 0V on my tongue, what is the LEAST that would happen to me

 

[erosennin]

No nothing will happen over your fingers.
On an open wound, or your tongue in this case, it will hurt a bit (a bit is qualitative as some people's bit is different to others). You shouldn't die.

Transformers are good =]], the only slightly problematic thing is - like everything else, when you run them at full power for a long time they get hot, but other than that, there is nothing to worry about it.
The X-former in your wall supply will be followed by a bridge recitifier, capacitor(s), voltage regulator and current bypass - unless it is a switchmode supply then it's different.

Power supplies are good, you will be surprised at the amount of money you save on batteries. Invest in a "bench supply" at some stage, they are good too.

 

[shaneshane1]

Thanks erosennin, now i dont seem so worried about getting electrocuted, also the connection on the transfomer is a female socket(like the ones that go into a radio) and i dont know how to use that to connect to my breadboard, is there something i can connect to it that just has to open wires?

 

[erosennin]

Yes. Cut it off =] (Make sure the power is not connected)
Then solder/connect it directly to your power line. One core will have a white stripe down it, and that one is USUALLY the ground - but check it with a multimeter or cro or other device.

 

[shaneshane1]

Yes. Cut it off =] (Make sure the power is not connected)
Then solder/connect it directly to your power line. One core will have a white stripe down it, and that one is USUALLY the ground - but check it with a multimeter or cro or other device.

Thanks, will do, one more question, i will be mostly be using a 5V regulator on my breadboard, can i still pull 5A from 5V instead of 12V, i know that my 7805 regulator only can draw 1A, but if it was rated at 5A would i be able to draw 5A from 5V?

 

[Hero999]

If it was rated at 5A you could draw 5A from it.

If you want a 5V suppply it would have been a good idea to buy a 5V supply, your LM7805 won't be able to take more than about 100mA for any lenght of time without a heatsink.

12V@5A is 60W, that sounds like a switchmode to me.

Strip the ends of some cable, tin them and poke them in to the socket.

You could just cut the connector off, tin the ends and wire it striaght to the breadboard.

 

[shaneshane1]

If it was rated at 5A you could draw 5A from it.

If you want a 5V suppply it would have been a good idea to buy a 5V supply, your LM7805 won't be able to take more than about 100mA for any lenght of time without a heatsink.

I said mostly 5V, sometimes i will require more than 5V, so thats why i got 12V, and it was cheaper than the others, and others were like 5V, 12V, 19V and only around 1.5 Amps, it seemed more worth it to buy the 5A one.

 

[Hero999]

You can get 5A 5A linear regulators but they're inefficient, if you want a chalanging project then build a DC-DC converter that will give you 10A at 5V from your 12V 5A power supply.

 

[Speakerguy]

I would use something like this to get 5V at high current from your 12V supply:

https://focus.ti.com/docs/prod/folders/print/ptn78020w.html

We use these type of things a lot at work and they are quite good. You may also notice they provide free samples. Just sayin, ya know.

Also, you REALLY do not want to do this with linear regulators. I had to make a 6 amp constant current source that would float up to 10V one day out of scrap parts. I paralleled two LM338K TO-3 devices to get the 6A current, stuck them on a good sized heat sink, and put a table fan blowing over it. I had no idea how hot those things could get. You really don't want to go that route. The heatsink extrusion alone would cost more than one of those switching regulators from TI.