Wouter,

 It wouldn't hurt to use a resistor that has a higher power rating than 
 the one you are using, providing you have the room to put it in the 
 circuit.   This will give you a little more headroom in the worst case
 power dissipation area.   You may not know into what the end user will be
 installing these units.  And therefore, there may not be enough airflow to 
 properly carry away the dissipated heat.  So going to a higher power
 resistor will alleaivate this problem somewhat by being able to retain
 more heat so that failure doesn't occur.

 Just a thought.


                                                     Regards,

                                                       Jim



>> Loose end caps
>> Seen it once years ago. The resistor was intact but the end 
>> caps weren't
>> connecting properly. The one I found had spent its life being 
>> heat cycled.
>> When the cap was removed the resistor was still ok inside. 
>> Cant explain two
>> in parallel going o/c over current maybe
> 
> These units were tested a few days ago, and I can't imgaine having
> missed this. 
> 
> Moderate overcurrent (or rather: overheating) can be spotted easily by
> clor, wrinkling and smell. I would expect severe overcurrent to have
> even more spectacular results. But these resistors looked perfectly OK.
> 
>> YES. It is a common failure. Usually caused by high starting current. 
>> You need to use wirewound or metal film types, not carbon.
> 
> OK, I'll switch to wire-wound.
> 
>> This is a common failure mode for metal film resdistors. Low-value
> 'carbon' resistors 
>> are often in fact metal-film.
> 
> OK, I get the message :) I'll definitely switch to wire-wound!
> 
> Wouter van Ooijen
> 
> -- -------------------------------------------
> Van Ooijen Technische Informatica: www.voti.nl
> consultancy, development, PICmicro products
> docent Hogeschool van Utrecht: www.voti.nl/hvu
>  
> 
> -- 
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist


-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist