I have an unusual application that might be great for EMC2. I have a small block of aluminum that need to be heated to a specific temperature. Currently we put it in a chamber, and heat the chamber to... let's say 80 degrees C. Soak for 1/2 hour an it's ready to test. When it comes out, and I need to cool it off, I put it in contact with a big block of Al at room temperature, and in about 2 minutes it's close enough to room temperature for further use.
I imagine a setup where three 500 watt halogen bulbs in series (giving maybe 250 watts worth of heat, and a lifetime that will outlive me) are nestled in an aluminum plate. One of those glass bead thermistors (see Re: [Emc-users] Multiplexers) senses the surface temperature on the side opposite the heating elements. It should be simple to set up EMC2 to accurately set that temperature quickly with proper PID values. Now I sandwich my block of aluminum between this heat source, and a plate underneath it with another thermistor. I set the temperature of the top block to be 10 degrees hotter than I want, assuming the center of my object is halfway between the temperature of the top plate, and the temperature of the bottom plate. When the bottom plate gets to 9 degrees short of the temperature I want, I start to back the temperature of the top plate down, with the intention of having them meet in the middle. When the temperature difference between top plate and bottom plate is about 1 degree, I could have the PC buzz a speaker, letting me know I can make a measurement. The nesting of PID loops occurs because the temperature of the top plate becomes the commanded temperature for my block of aluminum, and the temperature of the bottom plate becomes my actual temperature for the inside PID loop. Since the temperature control doesn't need sub second speeds, any old PC, even one still using the on-board video should be fast enough for this purpose, unless we read temperature using the game card method. A fast thread can discharge a capacitor to ground, then release it and start counting. A comparator will change state when the voltage passes that of the thermistor. Then EMC2 takes that integer value, looks it up in a table, and passes on the temperature in degrees C to the PID loop. * What I need help with is how to implement this. I can picture setting the target temperature using G-code, perhaps setting it up as a very slow spindle that needs to come up to speed, but that sounds too kludgey. I suspect that a separate GUI program tied into HAL might be a more appropriate way to do this. I am also wondering if classic ladder would be appropriate. Any ideas?* I think temperature control is one area that if we set up some good instructions to make it easy on a beginner, or perhaps even set up some temperature configurations in the drop down list of sample machines, we might get some users outside of the CNC arena. As I wrote that, I thought about the wiki page on stepper motors (guilt, guilt) that I have in the works. It's fairly far along, so maybe I should post it, and tweak it as others read, and point out anything that's unclear. ------------------------------------------------------------------------------ The ultimate all-in-one performance toolkit: Intel(R) Parallel Studio XE: Pinpoint memory and threading errors before they happen. Find and fix more than 250 security defects in the development cycle. Locate bottlenecks in serial and parallel code that limit performance. http://p.sf.net/sfu/intel-dev2devfeb _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
