At 12:46 PM 8/12/97 +0930, you wrote: >>Yes. I turn off everything that has a switchmode supply in it which is >>not a brand name product by the biggest companies. So therefore, I use > >Do you pay attention to things like UL ratings? Only when they apply to products from the top brand name companies, I've seen a manufacturer in Shanghai who churned out these UL labels by the thousands each day and sold them to anyone ! >Nice idea that. Unfortunately, in some cases, by the time a sufficient >volume of smoke makes its way to the smoke sensor, its a little late - >you've got a self-sustaining fire. But it would stop electricity from >becoming involved further. If I could, I'd use a CO sensor, since the detection of partial combustion can be much sooner than self sustained combustion and may very well give more time to have the fire NOT start if the power was removed etc. >Um, not nice. Be easy to make a cheap PIC cct that monitored freezer temp, >and wrote info in NV memory to indicate dangerous temperatures. Good app >for the 8pin device. Someone mentioned a bag of icecubes - now thats a nice simple solution, well it would turn into a solution if the power went off ;-) >But Mike, if they're made in humid conditions, then that implies low static >risk! Oh yeah - faith again mike - close proximity to plastic bags when sliding etc is unlikely to be dissipated by high humidity, I recall some early science experiments where water droplets were charged up etc.. >Not implying faith, more pragmatism... You can never reach 100% >reliability - so at what level do you declare a product ready to ship? This is a good point. If something is going to be used in an unattended environment then I would have more than one fail safe mechanism, like a PTC and fuse and regulators with thermal and current shutdown etc >>A faithful switchmode power supply is 'almost' an oxymoron ! >Yet you put your faith (sorry, that word again) in linear power supplies? No. Just because I don't like the way many SMPS are made does not imply I like linears, these also need care in design and construction. >They use semis too, and a fault in them could cause the transformer to cook >off - and cause a fire... PTC's only work up to a certain (power) level. True - so I get a transformer from a brand name supplier that already builds the PTC into the transformer - for unattended products, let them carry the can... >And not all manufacturers fuse them adequately. True, so I always design my own for unattended operation. I'm quite happy to mess around with cheap non brand stuff but never use it for anything which might end up in a risky scenario or for unattended operation. Rgds Mike Perth, Western Australia