New Classic Finds and etc. (Long)

From: Jim Battle <frustum_at_pacbell.net>
Date: Mon Jan 26 01:54:08 2004

Lyos --

Power supplies are almost always supply constant voltage, not constant
current. The current rating is the maximum amount of current they can
supply while still nominally achieving their specified voltage rating.
If you hooked up a "5V 1000A" power supply to something that normally
required "5V 350 mA", nothing bad would happen.

Also, it seems just wrong to say that giving even 1 mA too much to a
device could kill it. For example, supplying 801 mA instead of the
stated 800 mA would mean that the power supply would have to have 0.125%
constant current regulation -- a very tough spec to meet.

Probably the most common constant current application that comes to mind
would be RS-232, but even there, most people just use +/- 12V with a
resistor instead; for most applications the healthy margin in the spec
is enough that things work anyway.


Lyos Norezel wrote:
> Doc... this is a BAD idea... I've fried numerous devices by using the wrong power rating... even if it was only 1mA off. The voltage almost never matters... as long as the power is correct. Hope this gets to u before you fry your machine.
> Lyos Gemini Norezel
>
> Doc Shipley <doc_at_mdrconsult.com> wrote:
>
> Funny coincidence, there. I just hacked a Sprint CAD-1000 AC adapter
> onto a JetDirect Ex+ last night. The receptacle of the JD is odd, so I
> had to pull the board and solder the adapter direct. Other than that,
> it's the right voltage, and a little over-amped (1A vs the JD's rated
> 800mA).
Received on Mon Jan 26 2004 - 01:54:08 GMT