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<div class="moz-cite-prefix">Brian,<br>
Here's a PTC fuse that you can just put in your PS circuit to
limit your supply to about one amp. If you're using a "wall wart"
style supply it will be fully isolated and there's no difference
between the negative and positive sides of the supply, but in
other circumstances you'd need to put the fuse in the positive
side of the supply, usually just before the power or connector, so
best to just do that by habit. This device becomes an "open
circuit" when the current exceeds the trip value, then goes back
to a very low resistance a short while after the current drops. It
beats the hell out of buying fuses and horsing around with fuse
holders.<br>
However, a few simple tests may confirm that this issue is moot
with your supply because it turns itself off with a short. It
depends on the design of the supply, but for the last several
years manufacturers have found it much better to make a smart
supply that saves them from liability cases vs using a simpler,
dumb supply that will just cook in its own juices if shorted.<br>
<br>
<a
href="http://www.newark.com/jsp/search/productdetail.jsp?id=06R3405&Ntt=06R3405">Newark
part # 06R3405 1.1A hold 2.2A trip Multicomp MC33158 PTC fuse<span
style="color: rgb(85, 85, 85); font-family: Verdana, Arial,
Helvetica, sans-serif; font-size: 11px; font-style: normal;
font-variant: normal; font-weight: normal; letter-spacing:
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text-indent: 0px; text-transform: none; white-space: normal;
widows: auto; word-spacing: 0px; -webkit-text-stroke-width:
0px; display: inline !important; float: none;"></span></a> <br>
<br>
You can still overheat and "smoke" components with an ampere.
This won't save you from mistakes like getting a transistor almost
but not quite turned on, asking too much of a voltage regulator,
etc.<br>
<br>
-Pete<br>
<br>
<br>
<br>
On 10/17/2013 12:01 AM, Scott Hall wrote:<br>
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<blockquote cite="mid:525F6134.1070507@gmail.com" type="cite">
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<div class="moz-cite-prefix">Not at all -- but I would protect my
circuit with a fuse or other current limiting device. Otherwise
you're liable to release the magic smoke that makes the devices
work. :)<br>
<br>
On 10/16/2013 02:14 PM, Grawburg wrote:<br>
</div>
<blockquote cite="mid:37a494307a3e9599ffb179090b0f5c4d@myglnc.com"
type="cite">
<pre wrap="">I have a good 12 VDC 3A power supply. If my project only requires 300 - 400 mA is there any reason
why I can't or shouldn't use my power supply?
Brian Grawburg
Wilson
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<pre class="moz-signature" cols="80">--
Scott G. Hall
Raleigh, NC, USA
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:ScottGHall1@GMail.Com">ScottGHall1@GMail.Com</a>
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