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Kai Klaas
02/14/06 07:14
Read: 561 times
Germany


 
#109946 - Fire risk
Responding to: Oliver Sedlacek's previous message
Oliver said:
I forgot to mention that you should have some protective components around the LED because spikes will shoot straight through the cap. It's what they invented transzorbs for.

Transzorbs cannot solve all problems. The mess of these caps in series with mains is, that if bursts or surges are arriving from mains all eventual current limiting components are heavily overstressed. This means, that current limiting parts must be designed with lots of headroom, making them big and costly again.
Another issue is that such circuits using caps in series with mains do always suffer from relevant fire risk, because there's no limit for excessive voltage spikes on mains guaranteed.
Using a mains transformer for this task is much safer, because these parts are designed to withstand voltages of several thousands of volts.

Kai

List of 34 messages in thread
TopicAuthorDate
monitoring mains voltage      Per Guldmann      02/13/06 04:38      
   Opto with capacitor      Oliver Sedlacek      02/13/06 06:33      
      re opto with cap      Per Guldmann      02/13/06 07:09      
         Some protective components required      Oliver Sedlacek      02/13/06 09:56      
            Fire risk      Kai Klaas      02/14/06 07:14      
   Transformer        Andy Neil      02/13/06 07:49      
      thats the best chioce      Abhishek Singh      02/13/06 07:51      
      There's nothing wrong      Per Guldmann      02/13/06 08:40      
         Space      Andy Neil      02/13/06 09:32      
   please do not go aargh      Erik Malund      02/13/06 08:48      
      Opto isolator = LDR + Neon?      Andy Neil      02/13/06 09:20      
      10mA?      Oliver Sedlacek      02/13/06 09:53      
         Hmmm      Per Guldmann      02/13/06 10:12      
            Why not...      Steve M. Taylor      02/13/06 17:03      
               Neon + Photodiode      Andy Neil      02/14/06 00:31      
                  Loosing brightness      Kai Klaas      02/14/06 06:05      
   Transformer isolation is needed!      Kai Klaas      02/13/06 19:42      
      Previously, on 8052.com      Andy Neil      02/14/06 00:29      
         Safety first      Per Guldmann      02/14/06 03:11      
            Transformer      Kai Klaas      02/14/06 05:58      
               Sorry      Kai Klaas      02/14/06 07:18      
                  two places to look      Erik Malund      02/14/06 07:26      
                  Annoying, isn't it?!      Andy Neil      02/14/06 08:23      
                     Thanx!      Per Guldmann      02/14/06 08:35      
                        maybe Amveco 6200 series?      Erik Malund      02/14/06 08:37      
                        Transformers      Anders Sandström      02/14/06 11:01      
                     Could also be used      Kai Klaas      02/14/06 10:05      
   an Idea        Mahmood Elnasser      02/14/06 10:42      
      The simplest ideas are the best      Jez Smith      02/14/06 14:58      
         Poor dads      Mahmood Elnasser      02/14/06 23:12      
            Tainted food      Kai Klaas      02/15/06 08:25      
      Yes, but...      Kai Klaas      02/14/06 20:01      
         Low current      Mahmood Elnasser      02/14/06 22:50      
            Exactly!      Kai Klaas      02/15/06 08:40      

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