Hot end failure SD3 and PID settings

Well the PID is courtesy of 3rd party open source software, not Solidoodle.

My PID maintains within 0.5 deg C while printing.

How are you ascertaining the I term's contribution?

I watched the graphs.

When the temp goes above set-point you can tell the I is winding up in the negative direction by watching it just as it falls past the set-point(doing this with D at zero).  In a normal thermal PID system you clamp the "I" at a min of 0 so it cannot windup backwards.

On a normal PI thermal system AS SOON as you drop below set-point P should be calling for power, but it does not.  It waits till the "I" unwinds and then slams the system with 100% power.  This ends up being a 10 C drop, until it calls for power.  If I was clamped at 0 like  it should, then even if you drop 1 deg below set-point it should be calling for at lease a small percentage of power.

ADDED:
Autotune are for static systems.  These printers are both static and dynamic systems.  It really needs a FeedForward+PID system.

Since we know how much plastic we are putting though we can use that to call power ahead of time before the system sees a drop it temp.

I'm pretty sure the Marlin firmware constrains the I term contribution to [0, var], at least lawsy's fork. Not sure what ends up on the SD by default.

From temperature.cpp:

    temp_iState_min[e] = 0.0;

FF control is in my opinion an unnecessary complication for this plant. Properly tuned PID with a normally functioning heater and thermistor holds temps within a degree or two for everyone I know of with a solidoodle.

By the way, watching the graphs isn't a reliable way of figuring out each term's contribution. You should be able to turn on debugging, which will echo actual temp, each term's contribution, and desired heater power to the log window.

I will look more into once I get the hot end fixed.  I had turned on logs, but the get recycled every start of the host program and did not save it before it got erased. 

Anyone know the part number of the power resistor used in the hot end.  I would like to just fix it myself if I can. 

I am looking at the code right now.

I also see that PID loop only calculates if the error is +/-10.  If the error is +/-10 then it is either full on or full off.  This could be why I had seen Bang-Bang behavior.  So, not a full PID system. PID only when your in that +/-10C window.  Outside of that range it never calculates P, I or D(or if you swing outside of that it freezes the PID terms). 

I do see the limit for the I term in there, but now I see it is not full PID I get what I was seeing.  Still curious why I saw no power being put out when I the temp just dropped below setpoint(P should have been calling for power). 

Also since the resistor failed I may have been fighting that in the tune.

I have a company called TeslaTech, LLC, but I don't work for Tesla Motors.  My day in day out job is working for Trenchless Technology Center designing and integrating Ultra-Wide band ground penetrating radar systems.

My friend gave me the nick name tesla when I built a tesla coil in my parents garage at 15 years old and convinced my parents it was safe.

Just as a note, I haven't changed any of the PID algorithm in the solidoodle2-marlin fork. I did, however, set the P,I and D values to the preset 'Makergear' hotend, as the original hot ends came from them.

Everyone should do a M303 S190 when they get their printer and enter the PID values into the EEPROM storage.

The original heater resistor has part number ACS-5S-4R7-J and has 4.7 Ohm and 5 Watt.

A resistor that works as a replacement is AC03000006808JAC00 (6.8 Ohm, 3 Watt).

Edit: Here's a picture of the original and the replacement where you can see the part number: http://i.imgur.com/0URHujUh.jpg

Still haven't been able to find stand alone brass barrels, anyone have a source?