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Topic: Recommendation wanted for analog pressure sensing 0-512 psi (Read 2172 times) previous topic - next topic

Morris Dovey

Thanks. I understand (and appreciate!) your suggestion, but a quick look at my test sequence control function should provide you with some insights as to why I want the capability I asked about:

Code: [Select]
/*----------------------------------------------------------------------------*/
/* Find a complete set of LENR ignition (pressure,temperature) pairs          */
/*----------------------------------------------------------------------------*/
void lenr(void)
{  startup(0-0);                       /* Configure hardware for operation    */
   note0("Startup complete");          /* Log startup completion              */
   /*-------------------------------------------------------------------------*/
   /* Run a sequence of tests at progressively higher pressures               */
   /*-------------------------------------------------------------------------*/
   for (tgt_p = min_p; SAFE && (tgt_p <= max_p); tgt_p += inc_p)
   {  note1("Testing pressure",tgt_p);
      /*----------------------------------------------------------------------*/
      /* Run a sub-sequence of tests at progressively higher temperatures     */
      /*----------------------------------------------------------------------*/
      for (tgt_t = min_t; SAFE && (tgt_t <= max_t); tgt_t += inc_t)
      {  saf_t = tgt_t + mar_t;
         note1("Target temperature",tgt_t);
         note1("Safety threshold",saf_t);
         /*-------------------------------------------------------------------*/
         /* Perform a single LENR reaction test (t0 is global current temp)   */
         /*-------------------------------------------------------------------*/
         warmto(tgt_t);
         if (SAFE && (t0 >= tgt_t) && sustain(tgt_t))
         {  note1("Sustained",t0);
            break;
         }
      }
      note0("Temperature sequence complete");
      if (SAFE) coolto(min_t = tgt_t - 10);
   }
}
There's always a better way!

robtillaart


(running a nuke with an Arduino reminds me of the move CHina syndrome (?) in which a nuke plant was operated by C64's).

Quote
If the devices are linear, the mapping is trivial - but if the device used isn't linear, then the Arduino mapping function won't be adequate. That part of the problem shouldn't be difficult, but should probably wait for device selection, yes?

Check multiMap for this - http://arduino.cc/playground/Main/MultiMap -

Furthermore a remark just based upon my gut feeling. Never build a nuke myself.
I see in your lenR code a nested loop - temperature loop inside pressure loop - and if I recall my physics correctly these two are allways correlated except for adiabatic processes (P.V)/(n.T) = R . My gut feeling says that you should check both pressure and temp in every iteration.

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Morris Dovey

I've never built one before, too.   :smiley-mr-green:

I originally planned to use a BeagleBoard, but the application isn't all that demanding - and the little Mega2560 combines a better mix of the I/O capabilities I need with adequate speed and memory to do the job. I'd have liked it better if it had an FPU, but I can manage without.

I'm monitoring and logging pressure, temperature, and radiation level at 1Hz in a dedicated task. Each time samples are taken the code examines all three values, and calculates both first and second derivatives of pressure and temperature with respect to time. I think these will be enough for early detection of behavior instability.

Even though my startup() function includes subjecting the reaction chamber to a vacuum (twice) to remove oxygen, I'm concerned that water vapor could be produced by the H2 reduction of oxidized Ni (fuel) or Cu (reaction chamber inner wall). Water vapor pressure is described by the Antoine Equation up to its critical point, above which it behaves like an ideal gas with a very large R value. I have a graph at http://www.iedu.com/Solar/Engines/Hydrodyne/AntoineEq.html that contrasts the behavior of water with an ideal gas. It's an eye-opener.

A large part of the code I'm writing is targeted at finding any possible excuse to scram the reactor. That's going to be an inconvenience, but I intend to understand everything I can before I "soften" the code's "twitchiness".
There's always a better way!

robtillaart

Quote
I'd have liked it better if it had an FPU, but I can manage without.

familiar with this one?
- http://www.micromegacorp.com/umfpu-v3.html -
- http://www.micromegacorp.com/downloads/documentation/Arduino-uMFPU%20V3_1.pdf -

disclaimer : no experience with it, it is still somewhere on a todo list ..
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Morris Dovey

Looks interesting. Perhaps you can move it closer to the top of your to-do list?
]:)
There's always a better way!

robtillaart

The FPU costs ~$20* but when I order it from the US transport and import tax doubles (Or more) the price. I just send sales@Micromega a mail if they know a local reseller in the Netherlands. Or how to solve it otherwise. It would be great to have this one in shield form, with SPI and a free to choose pin for chip select.

* prices in Europe are higher and transport & tax are ~similar :(


Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Morris Dovey

#21
Apr 09, 2012, 07:41 pm Last Edit: Apr 09, 2012, 08:09 pm by Morris Dovey Reason: 1
If you can't find a reasonable-cost solution, e-mail to exchange addresses, buy online, and have it shipped to me. I'll re-mail it to you (as a "gift") and you can reimburse my mailing cost to my PayPal account.

Doing business with US companies should not be this difficult. :(
There's always a better way!

robtillaart

Quote
Doing business with US companies should not be this difficult.

the companies are not the difficult part ;)

I'll keep your offer in mind.
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Morris Dovey

Ok - as for the shield, I think you can download a free version of EagleCAD (http://www.cadsoftusa.com/) to design, and (elsewhere) get PCB's made in very small quantities for less than $10/board.

if you go this route, and aren't familiar with EagleCAD, there are some excellent training tutorials on YouTube (I've been working my way through those in my spare time). See https://www.youtube.com/watch?v=qG0O9LKH-_E
There's always a better way!

robtillaart

#24
Apr 09, 2012, 10:12 pm Last Edit: Apr 09, 2012, 10:17 pm by robtillaart Reason: 1
or use one of these - http://www.adafruit.com/products/51 - or - http://www.arduino.cc/playground/Tutorials/Protoshield - (brd file included ;)

or - http://www.nuelectronics.com/estore/index.php?main_page=product_info&cPath=1&products_id=3 -  ~$8  cannot design them for that price ...
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

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