[TriEmbed] Power Supplies

[Pete Soper]

Brian,
    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.
    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.

Newark part # 06R3405 1.1A hold 2.2A trip Multicomp MC33158 PTC 
fuse<http://www.newark.com/jsp/search/productdetail.jsp?id=06R3405&Ntt=06R3405> 


   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.

-Pete



On 10/17/2013 12:01 AM, Scott Hall wrote:
> 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. :)
>
> On 10/16/2013 02:14 PM, Grawburg wrote:
>> 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
>>
>
>
> -- 
> Scott G. Hall
> Raleigh, NC, USA
> ScottGHall1 at GMail.Com
>
>
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