XPost: sci.physics, alt.solar.thermal   
   From: bobnospam@gmail.com   
      
   amdx wrote:   
   > Snips   
   >   
   >   
   >> If ignition occurs, there will be another latency as heat is   
   >> transferred from the containment vessel into the heater tube - but I   
   >> think that situation would exist for any affordable strategy.   
   >>   
   >> The change in resistance looks like it'll be small, and I guessed   
   >> that an op-amp circuit might be useful to produce a larger   
   >> temperature swing. A temperature range of 25-537°C would probably be   
   >> a sensible design target. (I'm /aware/ of op-amps, but I've never   
   >> designed a circuit that actually /used/ one of the little buggers.)   
   >>> A linear output would be "nice to have", but isn't essential - I   
   >>> don't   
   >> think a table look-up/interpolation is likely to overburden even the   
   >> little Arduino.   
   >>   
   >> -----   
   >>   
   >> For my first go at this problem, I plan to start at a very low H2   
   >> pressure and increase it incrementally. At each pressure setting I'll   
   >> start at a low temperature setting and increase the temperature   
   >> incrementally to some safe limit (probably 250°C)   
   >> The entire exercise is to discover whether a self-sustaining reaction   
   >> can be initiated and, if so, the minimum (pressure,temperature)   
   >> values.   
   >   
   >  Hey Morris, is there a reason you don't want to stick a thermocouple   
   > in the tube for your temp measurements as others have suggested? It   
   > would sure simplify this section, and, you could get lots of design   
   > help on sci.electronics.design to raise the thermocouple output   
   > voltage nearer 5v at 537*C.   
   >  Also I suspect you have thought that if the temp sustains itself or   
   > starts to run away, your Ardiuno will sense this and start limiting   
   > hydrogen input and/or pump more water.   
   >                              Mikek   
      
   My concern if he is switching a relay on/off to control temp, is that the   
   on/off   
   time will be large per cycle. Using a thermocouple controller operating an SCR   
   or other such switch gives significantly finer and quicker, more proportional   
   control to avoid overruns. But, it might cost a couple hundred $, and Morris is   
   operating on a tight budget. If this is really dealing with nuclear reactions,   
   maybe the control is important. He doesn't want a runaway reaction.   
      
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