From: baron.nospam@linuxmainiac.nospam.net   
      
   John Fields wrote:   
      
   > On Sat, 20 Oct 2007 22:42:37 +0100, Baron   
   >  wrote:   
   >   
   >>John Fields wrote:   
   >>   
   >>> On Sat, 20 Oct 2007 00:15:56 GMT, "Farticus"    
   >>> wrote:   
   >>>   
   >>>>   
   >>>>"John Fields"  wrote in message   
   >>>>news:519ih3dgdj0lg36f01a48e6887ehk8a988@4ax.com...   
   >>>   
   >>>>> From the point of view of cost, I like the idea of a single   
   >>>>> phase-controlled TRIAC driving both heaters in parallel since the   
   >>>>> pair of heaters, in parallel, will only need 10A from the mains   
   >>>>> and, with proper timing, the loads will never see more than 120V.   
   >>>>>   
   >>>>> When one is unplugged, of course, the TRIAC need only pass 5A.   
   >>>>> Even better.   
   >>>>>   
   >>>>> But what's a simerstat?  Is it a device with feedback which will   
   >>>>> maintain a temperature once set, or is it like an open-loop lamp   
   >>>>> dimmer?   
   >>>>>   
   >>>>>   
   >>>>> --   
   >>>>> JF   
   >>>>A simerstat is the term given by electrical wholesalers for a   
   >>>>control typically used to control a cooker plate. It is open loop.   
   >>>>The simmerstat has a bi-metal strip built into it that does the   
   >>>>"control". The simerstat usually incorporates a 1amp(or thereabouts)   
   >>>>rated contact that is used to control the cooker plate (element).   
   >>>>F.   
   >>>   
   >>> ---   
   >>> I'm confused.   
   >>>   
   >>> If the simerstat is used to control temperature and the bimetallic   
   >>> switch is used to switch the element on and off in order to maintain   
   >>> that temperature, then that's closed loop.   
   >>>   
   >>> An example of 'open loop' would be a lamp dimmer where there is no   
   >>> feedback used to control the brightness of a lamp.  Or, for another   
   >>> example, a VARIAC.   
   >>   
   >>Hi John,   
   >>   
   >>The simmerstat is only open loop in the sense you describe.  There is   
   >>no   
   >>sensing of the actual hotplate temperature.  The current through the   
   >>hotplate passes through a secondary heater wound around a bimetallic   
   >>strip.  This simply makes/breaks the circuit.  A cam controls the   
   >>distance the bimetallic moves.   
   >   
   > ---   
   > Got it, thanks! :-)   
      
   Your'e welcome.   
      
      
   --   
   Best Regards:   
                        Baron.   
      
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