WidenersInline FabricationRepackboxMidSouth Shooters Supply

Page 1 of 3 123 LastLast
Results 1 to 20 of 45

Thread: Dual PID Temperature Controller

  1. #1
    Boolit Master

    theperfessor's Avatar
    Join Date
    Dec 2007
    Location
    Evansville Indiana
    Posts
    2,746

    Dual PID Temperature Controller

    As part of a long term process of developing the technology and knowledge base to make custom bullet molds it was necessary to have available a means to control and monitor the temperature of a lead melting pot and a bullet mold. I decided to build a dual temperature controller using digital PID controllers, appropriate type K thermocouples, and other components supplied by Auber Instruments Inc.

    A PID controller is a device that compares the set point value (what you want) to the actual process value (what you've got) from your sensor over a period of time. PID stands for Proportional-Integral-Derivative. Proportional control merely looks at the difference between set point and process values to determine whether to turn on or off an output. A simple bimetallic thermostat operates this way, but this mode of control produces overshooting/undershooting and a constant cycling of the process value above and below the set point value Derivative refers to the rate of change of the process variable over time as control action takes place. Integral control is based on the total time and magnitude of the error between the process value and the set point value. These latter two modes are designed to minimize undershoot/overshoot and improve system stabilization. These particular controllers have a discrete (on/off) output; during operation the controller cycles it on and off for certain time periods to maintain control as closely as possible.

    The Auber PID controllers have a number of user-friendly features that make them work well for this type of application. They accept analog input directly from a thermocouple (and other sensors), can be operated on a range of input AC voltages, and can be had with internal relay outputs or DC outputs to operate external mechanical or Solid State Relays. They also can actuate external alarms (which I am not utilizing in this application), will auto-tune themselves, and are small and relatively inexpensive.

    Parts List
    2 - PID controllers Auber #SYL-2352 $89.00
    1 - Type K thermocouple w/6 probe Auber #WRNK-171 $13.50
    1 - Type K thermocouple -20 probe Auber #TC-K6 $6.85
    2 - 25A Solid State Relays Auber #RS1A40D25 $30.00
    2 - Panel mount thermocouple connectors Auber #TCCON $9.80
    1 - dual outlet 110VAC female socket $3.00
    1 - cable clamp $1.00
    1 - approx 48 of 1/4 x 6 6061 aluminum plate $24.00
    1 - fuseholder and box of 20A Type T fuses $5.00
    1 - tube of heat sink silicone grease $4.00
    1 - 110VAC three prong male plug -
    1 - terminal strip -
    1 - 6' 12 ga 3 conductor stranded rubber coated cable -
    miscellaneous 14 ga hookup wire (red, yellow, black, white) -
    miscellaneous crimp on connectors -
    miscellaneous screws -
    bits and pieces of repurposed shop scrap -
    (unpriced items are items I had on hand) Total* $186.15

    *(Total does not include the $19.50 for three orders from Auber; I should have made one order and saved $13.00)

    Construction
    I wanted to make a fairly compact unit so a 3-D CAD system was used to aid the design process. The Auber site has technical information on their products, including the dimensions of the major components. Other components that were on hand were simply measured using suitable tools. Each component was turned into a simple rectangular object and locate in space to enable the box to be built around it. The overall dimensions of the box ended up being 8" long, 4-1/2" high, and 6-1/4" deep. Once this was done it was easy to take the six box panels and locate hole centers and other relevant features. Each panel was then dimensioned and printed as an individual part to take to the machine shop..

    The box panels are made from 1/4 aluminum plate which was cut to size by sawing and milling. All the holes were drilled and counterbored where required using a vertical milling machine. The square holes in the front panel for the two PID controllers were milled, as were the holes for the thermocouple socket. The thermocouple sockets were designed to be mounted on 12 16 gauge sheet metal so these had to be recessed into the front to allow the rear spring clip to lock them in place. The area around the cable clamp hole on the inside of the right panel was also relieved for the same reason. The hole for the 110VAC socket was also milled out.

    The holes were tapped using a hand tapping machine.

    The bottom, front, and both sides were then clamped up to maintain size and squareness and TIG welded on the inside. The corner brackets used as attachment points for the top and back panels were then welded in place.

    The box was then returned to the mill and the holes for the top and rear screw holes were drilled, again followed by hand tapping. The box was then assembled to give it rigidity and clamped into the mill vise, where the bottom vent slots were cut. The top was removed and clamped in the vise and the vent slots were cut.

    All the components were given a thorough cleaning, first in a parts-washing tank, followed by a wipedown with acetone.

    The terminal strip for the 110VAC connections and the fuseholder were screwed into place first, followed by the cable clamp. The 110VAC cable was then anchored into place. The black (hot) lead had a female spade lug crimped on and then it was connected to the fuseholder. The white (neutral) wire was extended to the terminal strip where it was stripped at intervals and looped around the screws on one side of the terminal strip. The green (ground) wire was connected to one of the mounting screws on the end of the terminal strip, where it would ground to the case. A jumper wire with a female spade lug crimped on one end and stripped at intervals on the other end was used to connect the fuseholder to the terminal strip.

    The thermocouple wires were then cut off by about six inches to provide a length of wire to go from the thermocouple socket to the controller. The cut ends were stripped and bent into a loop. The thermocouple was connected to the male plug, and the short section was connected to the female socket., leaving the spade lugs unconnected for the moment. Polarity is very important here - my thermocouple wires were marked red positive and had a red thread in the wire covering.

    The SSRs are mounted with the power terminals on the bottom, where the terminal strip makes inserting the wire difficult, so 12 gauge black jumpers wire connected before they were mounted to the case. Heat sink grease was applied to the bottom of the SSRs before mounting.

    The PID controllers each had four eight inch long 14 gauge jumper wires connected black and white to the AC power terminals, red to the positive SSR coil output, yellow to the negative SSR coil output.

    The thermocouple sockets were inserted and anchored into place with the supplied spring clips. The PID controllers were inserted into the face and the retaining clips were put on loosely. The thermocouple wires were connected to the proper terminals on the PID controller, which was then securely anchored with the spring clip. The yellow and red wires hooked to the proper polarity terminals of the SSR, and the white and black wires connected to the 110VAC terminal strip.

    One of the power wires of the SSR was connected to a black (hot) terminal on the terminal strip. The other was connected to one of the brass terminals on the 110VAC socket. The 20A socket had the connector strip on the side removed so that each plug-in was controlled separately. The silver (neutral) side of the socket was not altered so only one white wire was needed to connect it to the terminal strip. No ground wire was used as the socket grounds to the box.

    The 110VAC socket was then mounted to the top panel and a metal cover was secured in place. A fuse was inserted into the fuseholder and the top and back panels were then mounted to the box. A three prong male plug was connected to the end of the power cable, completing the assembly.

    Operation
    The thermocouples were plugged in and the unit was plugged into a heavy duty extension cord on a 20A branch circuit. It was thrilling when nothing exciting happened and everything powered up normally. The units were preset at 50F and the thermocouples were exposed to ambient air temperature and within a few minutes both stabilized within one degree of the same 67-68F temperature reading.

    With everything working normally it was time to test the unit. A simple thermocouple holder for the Lyman 20 pound bottom pour lead pot was made from shop scrap. It allows the thermocouple probe to be inserted into the melt to a consistent depth and can be swung out of the way for fluxing when the probe is removed.

    Since a bullet mold was not available for preheating, a one pound lead ingot was drilled and tapped with a 1/4-20 thread and the other thermocouple was screwed into it. A protective aluminum plate was placed over the hot plate used for preheating and eight ingots, including the instrumented one, were placed on top.

    The Lyman furnace and hot plate were plugged into the appropriate sockets and both units were turned all the way one, effectively cutting out the thermostats built into each unit and allowing the PID controller to cycle the power to the devices. Again nothing exciting happened.

    The set point value of the controllers were then entered. The lead pot was set to 725F, the hot plate to 325F. Within a minute or two the temperature reading began to increase. Within 10 12 minutes the hot plate was approaching the desired temperature and the auto-tune function was engaged..It overshot the temperature by about 40F the first time but settled down within a few minutes and held temperature within about +/- 10F after a while. This was not unexpected, as it is a system with a powerful input to a low thermal mass with a lot of surface area exposed to air currents.

    Within about 20 minutes the lead pot was approaching the set point value and the auto-tune was engaged. It overshot by about 30F at first but stayed within +/-5F after that, with +/- 2F control most of the time. No material was added or removed from the pot at this time so how good control will be during operation is yet to be determined. It is expected that temperature swings can be minimized by preheating ingots to a consistent temperature on the hot plate.

    In the future I plan to attach a thermocouple to several special molds, but I do not plan to drill and tap all my molds. I think that putting a mold in the middle of a bunch of ingots held at a specific temperature on a hot plate would work just fine.

    The system was operated at steady-state conditions for several hours. At no time did the area of the side panels under the SSRs get warm enough to feel. No heat was felt coming through the air vents on the top. Despite the small size of the unit it runs cool. So far I am pleased with the results.

    Pictures
    Included here are various shots of the completed unit:
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	pid01.jpg 
Views:	588 
Size:	99.1 KB 
ID:	18315   Click image for larger version. 

Name:	pid02.jpg 
Views:	659 
Size:	99.2 KB 
ID:	18316   Click image for larger version. 

Name:	pid03.jpg 
Views:	567 
Size:	101.3 KB 
ID:	18317   Click image for larger version. 

Name:	pid04.jpg 
Views:	512 
Size:	99.7 KB 
ID:	18318   Click image for larger version. 

Name:	pid05.jpg 
Views:	573 
Size:	100.9 KB 
ID:	18319  

    Click image for larger version. 

Name:	pid08.jpg 
Views:	605 
Size:	100.2 KB 
ID:	18322   Click image for larger version. 

Name:	pid09.jpg 
Views:	562 
Size:	95.3 KB 
ID:	18323   Click image for larger version. 

Name:	pid10.jpg 
Views:	621 
Size:	78.3 KB 
ID:	18324   Click image for larger version. 

Name:	pid11.jpg 
Views:	576 
Size:	98.3 KB 
ID:	18325   Click image for larger version. 

Name:	pid12.jpg 
Views:	653 
Size:	98.8 KB 
ID:	18326  


  2. #2
    Boolit Master
    lwknight's Avatar
    Join Date
    Nov 2009
    Location
    Fort Worth, Texas where the west begins
    Posts
    3,416
    Now that is one nice setup!! You have a lot more patience than I do for sure.

    And I'm sure glad that you know how to use paragraphs, unlike a few wordy writers that make a page full of alphabet
    Sent from my PC with a keyboard and camera on it with internet too.
    Melting Stuff is FUN!
    Shooting stuff is even funner

    L W Knight

  3. #3
    Banned

    Join Date
    Jul 2009
    Location
    The Great Land
    Posts
    998
    Well Done!

    I had to look twice at the pid02.jpg - It looks like you have the smoke escaping

  4. #4
    Boolit Master

    theperfessor's Avatar
    Join Date
    Dec 2007
    Location
    Evansville Indiana
    Posts
    2,746
    There is some silicon grease on the left SSR and a little bit of reflection off my weld/work table in that shot that makes it look like a smoke pump in operation. Thanks for king words and previous assistance. It is appreciated.

  5. #5
    Boolit Grand Master



    Join Date
    Dec 2005
    Location
    Southwestern Ohio
    Posts
    8,456
    That is a worthy project - the report and images are VERY well done.

    Thanks for sharing with us.

    Dale53

  6. #6
    Boolit Buddy
    Join Date
    Aug 2006
    Location
    Davenport, IA
    Posts
    398
    I enjoyed this report and admire your ingenuity. Its nice to see how we can improve our setups and make the boolitmaking process more efficient. Now if I could just find the time and money.

    Paul

  7. #7
    Boolit Buddy
    Join Date
    Mar 2009
    Posts
    267
    Any further updates on how this is working?

    Do you get overshoots when the level of lead is lower in the pot?

    Also, is the mould temperature turning out to be constant? With the application and removal of heat from the uncontroled source (i.e. the poor of lead into the mould and removal of the casting on a somewhat irregular basis) I wouldn't expect it to.

  8. #8
    Boolit Grand Master



    cbrick's Avatar
    Join Date
    Dec 2005
    Location
    Kalifornia Escapee
    Posts
    8,036
    Where are the mods at? This isn't a sticky yet?

    Perfessor, I would like your blessing to make this an article for the lasc.us site.

    I use the Magma electronic temp controller but your idea of a second PID for mold temp is quite interesting. I also would like an update on temp stability as the level of alloy in the pot changes.

    One difference with the Magma pot is that the thermocouple attaches to a nut that's welded to the center bottom of the pot (on the outside). The heating unit wraps around the middle of the pot so there is a time delay before heat reaches the thermocouple. This unit more than cut in half the temp swings of the mechanical thermostat but temp still swings +- 15 degrees of the set temp (or about 30 degrees). Once the pre set temp of 700 degrees is reached and the power is shut off heat is still flowing to the thermocouple and it reaches about 715-717, as it cools with the power off and reaches the pre set 700 and switches on the temp continues to drop to about 685.

    As the level of alloy drops the temp is maintained within the same +- 15 degrees as apposed to continuing to increase as most electric pots do.

    Please keep us informed, fascinating project.

    Rick
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	DSCN2047-9.jpg 
Views:	332 
Size:	27.9 KB 
ID:	20443   Click image for larger version. 

Name:	DSCN2030-9.jpg 
Views:	281 
Size:	20.5 KB 
ID:	20444  
    "The people never give up their freedom . . . Except under some delusion." Edmund Burke

    "Let us remember that if we suffer tamely a lawless attack on our liberty, we encourage it." Samuel Adams

    NRA Benefactor Life Member
    CRPA Life Member

  9. #9
    Boolit Master

    theperfessor's Avatar
    Join Date
    Dec 2007
    Location
    Evansville Indiana
    Posts
    2,746
    You're more than welcome to make a sticky of this or post it on the lasc.us site.

    I haven't used it much as I have been running up a batch of 10 bullet mold blanks, 4 of 7075 aluminum, 4 of 2024 aluminum, and 2 of Dura Bar malleable iron. I've got the blocks and sprue plates nearly done and when I get them finished I plan to make one of each into some test molds with cavities running from .250 to .500 inch so I can plot mold cavity size versus bullet size for different alloys. That way I'll know what size to make a cavity to drop a bullet of a specific size for a given alloy.

    Right know I've got the students in my class finishing up a run of 2-lb lead head hammer handles and 00/0000 ball molds. Not only will the students get to keep their hammers and molds for their own use, but I will offer some of each engraved with the castboolits URL on them here for a site benefit/Ken benefit auction. Look for them about the first of May. Next week is our midterm break and I plan to make the hammer head mold then. If I have the time I'll make two of them and offer one of them for auction here also.

    We will have our Student Hammer Pour of 2010 in late April and I plan on firing up the small lead pot rig shown here to let the students cast some balls as well as hammer heads. Should get more performance data then which I will then post here.

  10. #10
    Boolit Master

    Join Date
    Aug 2005
    Location
    Wyoming
    Posts
    3,047
    Perfesor,

    Why in hades are you not in my area? I would love to have the cahnce to have a good instructor for machine tools. Hell I would just like to have the opportunity to take a class. I tis looking like I may be doing a 10 mile round trip to take a class out of state when/if it is offered again.

  11. #11
    Boolit Master

    theperfessor's Avatar
    Join Date
    Dec 2007
    Location
    Evansville Indiana
    Posts
    2,746
    I can't think of anything that might be more fun than having a bunch of the interested guys from here in a machining class. Can't complain about the students I have now, by the time I get them they're interested or gone, but a whole class of bullet casters - what a thought! I know I would learn a lot from you guys, just like I have from reading the posts here.

    Bet you'll have to pay more for out-of-state tuition unless there's a reciprocity agreement. Too bad. Hope you get in and enjoy yourself.

    I will start taking some pictures of the ball molds as we make them and post a step-by-step writeup of the process from start to finish here later, might be interesting to a few people.

  12. #12
    Boolit Master
    Lee's Avatar
    Join Date
    Oct 2005
    Posts
    928
    Buy your PID's right here on site for $20 each, with $15 going to the site! See Benefits........
    Been paddlin' upstream all my life, don't see no reason to turn around now.

  13. #13
    Boolit Master

    theperfessor's Avatar
    Join Date
    Dec 2007
    Location
    Evansville Indiana
    Posts
    2,746
    Sounds like a win-win to me. These little mini-PID controllers aren't much harder to
    hook up than a switch and doorbell transformer. And the site benefits from it. Cool.

  14. #14
    Boolit Buddy chrisx1's Avatar
    Join Date
    Feb 2008
    Location
    North Missouri
    Posts
    145
    Does anyone know of an easy way to use a PID to control a gas heat source? I use a propane burner on my shotmaker, and if there ever was a piece of equipment that needs constant temp regulation, it's a shotmaker.

    Chris
    NRA Life Member

    "The Constitution preserves the advantage of being armed that Americans possess over the people of almost every other nation, where the Governments are afraid to trust their people with arms." - James Madison.

  15. #15
    Banned

    Join Date
    Jul 2009
    Location
    The Great Land
    Posts
    998
    Sure, Shouldn't be too hard.

    See http://shop.ebay.com/items/gas solen...&tt_encode=raw

    provides a rather good sample of appropriate equipment.

    You will need to adjust some PID parameters, like duty cycle ect. and don't forget a few basic safety features.

    by adding a second solenoid you can even have a 2 stage burner.
    Add a third valve (manual) that provides about half the heat you need (it provides an 'idler heater) and you can light manually and you don't need a pilot light.
    Last edited by Frozone; 03-25-2010 at 01:33 AM.

  16. #16
    Boolit Master
    ANeat's Avatar
    Join Date
    Mar 2006
    Location
    SW Ohio
    Posts
    1,307
    Chris you would need some kind of valve for the gas. For example I have a gas heater in my garage with a thermostat. If you had that control valve with the PID switching the valve on/off you could control the burner. There would need to be either a pilot light or ignition transformer. You would probably want a 10 or 20 degree differential so the valve isnt shutting on/off right at the setpoint.

    Probably not an "easy" way I guess

  17. #17
    Boolit Buddy


    Join Date
    Nov 2009
    Location
    Oro Valley, AZ
    Posts
    278
    Quote Originally Posted by chrisx1 View Post
    Does anyone know of an easy way to use a PID to control a gas heat source? I use a propane burner on my shotmaker, and if there ever was a piece of equipment that needs constant temp regulation, it's a shotmaker.

    Chris
    Here is a link to the beer site which has a pid controller propane burner.
    <http://www.alenuts.com/Alenuts/brutus.html>

    If you look at the third photo down what you are looking at is a PID controlled propane burner. Where the pipe comes out of the rail there is a "T". One side of the "T" goes through a ball valve to a yellow hose. Note the ball valve is only partway opened. This is for a pilot light and you adjust the pilot with the ball valve. The vertical "T" pipe goes through a fully opened ball valve and then through a PID controlled solenoid to the burner. So when you are at temperature only the pilot is lit. When the temp drops the PID opens the solenoid valve and the pilot lights the gas burner. Pot warms up PID closes the solenoid valve and the gas to the burner shuts off leaving just the pilot light on. Pretty nice setup I thought.

    Starbits

  18. #18
    Boolit Buddy
    Lee W's Avatar
    Join Date
    Mar 2005
    Location
    Upstate NY
    Posts
    290
    The best way for gas burners is a proportional valve and a PID with an analog output. (either mA or V output.)

    Not a very cheap option.. (Ebay is the cheapest by every meaning of the word.)

    http://cgi.ebay.com/Festo-MPYE-5-M5-...item51916f6f24

    and

    http://cgi.ebay.com/Temperature-Cont...item518d5e3035

  19. #19
    Boolit Mold
    Join Date
    Sep 2011
    Location
    Southern Middle Tennessee
    Posts
    15
    Perfessor,
    Very nice work. Do you happen to have a wiring diagram for this unit? I think I have almost enough left over parts from past projects to build one and would like to be sure of the wiring.

  20. #20
    Boolit Master
    Mal Paso's Avatar
    Join Date
    Jun 2010
    Location
    Carmel, Ca
    Posts
    4,121
    I used those little TC-K6 probes with the threaded nut removed. The probe is rated 1800* so I silver soldered the probes into the bottom of the tanks. It's angled so the tip with the junction inside is right next to the valve rod and 1/2" off the bottom to avoid thermal drain. My first try was on the bottom but the reading was 40* low. Now I get perfect alloy temperature down to 5/8 ".
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	PID4.jpg 
Views:	1507 
Size:	87.8 KB 
ID:	35524  
    Mal

    Mal Paso means Bad Pass, just so you know.

Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check