Proportional Integral Derivative Controller

[jaysouth]

I just received a PID controller from a fellow member at castboolits.  The purpose of the device is to act as a temperature regulator on your lead pot.  I suppose it could be called a thermostat by non-scientific folks like me.

 

Anyway, I set the thing for 700 degrees f.  It kept my pot at this temp, plus or minus 5 degrees for a 2 hour casting session.

 

Using wheelweight alloy, I quickly began cranking out nice uniform bullets.  I look forward to experimenting with different temps for different alloys.

 

[URL=http://s1223.photobucket.com/user/jaysouth100/media/PID%20controller/DSCN0190_zpscb5c5b08.jpg.html][/URL]

 

[URL=http://s1223.photobucket.com/user/jaysouth100/media/PID%20controller/DSCN0189_zpsfde9adb2.jpg.html][/URL]

Edited January 28, 2014 by jaysouth

[Dolomite_supafly]

I need to build one of these. Everyone I have talked to says it makes a huge difference in how well the bullets come out.

[jaysouth]

Dolomite,

 

It was preset at 700 degrees.  Next casting session, I am going to experiment with a higher temp.

 

What have you found the optimum temp to be for wheelweight alloy?

 

I am not technical enough to understand everything about the device.  Apparently it is the marrage of a solid state relay, a PID unit and a probe that appears to have a K type connections.  It seems like the sum of all these parts is well under a hundred dollars, but I don't have a clue how to pick the right parts or marry them together.  I got this one from frozone at castboolits.  It was $185 plus shipping.  

 

If you build one, share with us.

[ttocswob]

You sir, win Thread Title of the Year.

 

And I'm still using an iron pot on my turkey fryer, so a little technical for me.

[Guest Broomhead]

I need one of those babies on my forge to control/read my temps. That would take a lot of the guess work out.

[Guest GimpyLeg]

For those who don't use any temp control....  please watch your over temps.  Lead does vaporize around 900 and can cause some bad issues.

[tnhawk]

What method of tuning did you use to set the algorithm parameters of the controller?  What range of temperature is desirable for casting bullets?

 

I've reloaded for years but haven't started casting yet.

Edited January 27, 2014 by tnhawk

[Dolomite_supafly]

This was in an email I received from a friend about building a PID.

From Radio Shack

Terminal block, 6 position

Spade connectors, small

Spade Connectors, Large

On/Off Toggle Switch

Project Box
Wire

From Auberins.com
SYL-1512A - PID controller I use -  or you can use the next one if you want to see set temp and actual temp at the same time
SYL-2362
MGR-1D4825 - 25A Solid State Relay
WRNK-191 - Thermocouple

 

 

 

I do not have a PID yet but I have measured my lead and it runs 650-700 and the mold itself runs 250. If you stay around those temperatures and increase or decrease the pour rate to keep the mold at temp you should be good.
 

[peejman]

I need one of those babies on my forge to control/read my temps. That would take a lot of the guess work out.

 

 

Get a multi-meter with thermocouple capability.

 

http://www.amazon.com/AGPtek-Channel-Digital-Thermometer-Thermocouple/dp/B0084JQL1Q/ref=pd_sim_sbs_indust_1

 

 

The above should work the same in the lead cauldron. 

[Dolomite_supafly]

Reading is one thing but actually controlling is another. Most need something that also precisely controls the temps.

[jaysouth]

What method of tuning did you use to set the algorithm parameters of the controller?  What range of temperature is desirable for casting bullets?

 

I've reloaded for years but haven't started casting yet.

 

It's pretty simple to set the temps to your desired temp.  Just like setting a digital clock.  A lot of casters think that 700 degrees f. is the optimum temp.  I was not pleased with the appearance of the bullets at that temp however.  Next session I will try 750 degrees.

[jaysouth]

Get a multi-meter with thermocouple capability.

 

http://www.amazon.com/AGPtek-Channel-Digital-Thermometer-Thermocouple/dp/B0084JQL1Q/ref=pd_sim_sbs_indust_1

 

 

The above should work the same in the lead cauldron. 

 

The device that you have linked to is a digital thermometer.  In fact, I have one exactly like it.  However it is not a multimeter and it will not control the current to your pot to maintain a constant temp.  If you buy one of these to measure the temps of your casting process, you will also need a stainless steel probe with K type plug.  The two probes that come with the thermometer are for inserting in ovens, AC ducts, etc.  They will  not survive the molten metal in a casting pot.

 

In the top photo, you can see the coiled cord of the K probe from the  item you linked to.

 

I am pleased with mine, I have used it for a lot more applications than tracking temps in my casting pot.  I just can't figure out how to calibrate it should the need arise.

Edited January 28, 2014 by jaysouth

[Dolomite_supafly]

It's pretty simple to set the temps to your desired temp.  Just like setting a digital clock.  A lot of casters think that 700 degrees f. is the optimum temp.  I was not pleased with the appearance of the bullets at that temp however.  Next session I will try 750 degrees.

 

How hot was the mold? The mold temp has more to do with how the bullets look than the lead temp. My lead pours perfect bullets at 650-700 degrees but only once the mold is up to temp. If the mold is not up to temp the bullets will be wrinkled and the square edges will be rounded and not very well defined regardless of the lead temp. You can have 900 degree lead and if you pour it into a cold mold the bullets will be wrinkled and not well defined. Now you can have lead that is 600 degrees and as long as the mold is hot enough the bullets will look great.

 

If your bullets come out with a frosty look to them and perhaps with what looks like a crystaline structure then the mold is too hot. At that point I open the mold and let it set for a few minutes to cool. It also depends on the alloy used. Pure lead will be very shiny, like chrome, while wheel weights will have a dull look to them.

 

Wrinkled bullets are caused by one of two things, the mold is too cold or the mold is dirty. A new mold MUST be cleaned. I clean using hot water, Dawn and a toothbrush. After that I try casting without smoking the mold and most times it doesn't need to be smoked. If it does need to be smoked do NOT use matches or candles because they will deposit an oily film that will cause the bullets to come out wrinkled no matter what temperature the lead or the mold is. If I have to smoke a mold I only use a lighter. I put a heavy coat of soot then I use a Qtip to lightly wipe the soot off. Then I repeat the sooting and wiping two more times. When done the mold should not look clean but should have a tarnished look to them.

 

This is how I cast. I turn the lead up to ~650-700 degrees depending on outside temperature. I set my mold on top of the pot to allow it to warm some as the lead melts. Once the lead is melted I start casting and I cast as fast as I can. I do not look at the bullets until I have about 20 drops. At that point I start paying attention to the bullets. You will see them go from wrinkled or not well defined to nice looking bullets. But I continue to cast as fast until I see part or all of the bullet get frosty. At that point I start slowing down the casting rate until the bullets start casting nice looking bullets again. Then you will have to speed up or slow down a few more times until you figure out the rate.

 

The lead temp regulates how fast you can cast. If the lead temp is lower you can cast at a faster rate without the mold over heating but if the lead is a higher temp it requires a slower rate to prevent the mold from over heating.

[tnguy]

The device that you have linked to is a digital thermometer.  In fact, I have one exactly like it.  However it is not a multimeter and it will not control the current to your pot to maintain a constant temp.  If you buy one of these to measure the temps of your casting process, you will also need a stainless steel probe with K type plug.  The two probes that come with the thermometer are for inserting in ovens, AC ducts, etc.  They will  not survive the molten metal in a casting pot.

 

In the top photo, you can see the coiled cord of the K probe from the  item you linked to.

 

I am pleased with mine, I have used it for a lot more applications than tracking temps in my casting pot.  I just can't figure out how to calibrate it should the need arise.

 

Depends how precise you want the calibration and if you have a known-good source available.

[jaysouth]

TNguy,

 

Mechanically, or digitally, as the case may be, I do not know how to calibrate the digital thermometer linked to above.  It's not covered in my instruction booklet.  However, a known source, regarding temperature, is ice water.  Fill a glass with ice to the brim, fill with water.  In ten minutes the water temp will be exactly 33 degrees f. for about the next 10 minutes.  Insert your thermometer and adjust to 33 degrees.

 

This is a trick that health inspectors used to use to test the calibrations of stem thermometers in restaurants.  But it still works.

[jaysouth]

How hot was the mold? The mold temp has more to do with how the bullets look than the lead temp. My lead pours perfect bullets at 650-700 degrees but only once the mold is up to temp. If the mold is not up to temp the bullets will be wrinkled and the square edges will be rounded and not very well defined regardless of the lead temp. You can have 900 degree lead and if you pour it into a cold mold the bullets will be wrinkled and not well defined. Now you can have lead that is 600 degrees and as long as the mold is hot enough the bullets will look great.

 

If your bullets come out with a frosty look to them and perhaps with what looks like a crystaline structure then the mold is too hot. At that point I open the mold and let it set for a few minutes to cool. It also depends on the alloy used. Pure lead will be very shiny, like chrome, while wheel weights will have a dull look to them.

 

Wrinkled bullets are caused by one of two things, the mold is too cold or the mold is dirty. A new mold MUST be cleaned. I clean using hot water, Dawn and a toothbrush. After that I try casting without smoking the mold and most times it doesn't need to be smoked. If it does need to be smoked do NOT use matches or candles because they will deposit an oily film that will cause the bullets to come out wrinkled no matter what temperature the lead or the mold is. If I have to smoke a mold I only use a lighter. I put a heavy coat of soot then I use a Qtip to lightly wipe the soot off. Then I repeat the sooting and wiping two more times. When done the mold should not look clean but should have a tarnished look to them.

 

This is how I cast. I turn the lead up to ~650-700 degrees depending on outside temperature. I set my mold on top of the pot to allow it to warm some as the lead melts. Once the lead is melted I start casting and I cast as fast as I can. I do not look at the bullets until I have about 20 drops. At that point I start paying attention to the bullets. You will see them go from wrinkled or not well defined to nice looking bullets. But I continue to cast as fast until I see part or all of the bullet get frosty. At that point I start slowing down the casting rate until the bullets start casting nice looking bullets again. Then you will have to speed up or slow down a few more times until you figure out the rate.

 

The lead temp regulates how fast you can cast. If the lead temp is lower you can cast at a faster rate without the mold over heating but if the lead is a higher temp it requires a slower rate to prevent the mold from over heating.

 

 

If you are thinking about casting, read, the reread this post a couple of times.  I have been casting for a long time and I see something in this post that I need to do next session.

 

I keep my molds on a single eye electric hotplate while I am casting.  I can see by reading above, that sometimes my molds are too hot.

 

Next session I am going to set the PID for 650 degrees and not heat my molds so much. 

[jaysouth]

For anyone interesting in a DIY PID controller, here is a very exhaustive discussion, with good illustrations and diagrams over on castboolits.

 

http://castboolits.gunloads.com/showthread.php?115724-Project-PID-on-Lee-Pro-4-20-furnace

 

I chose to buy one outright.  It would appear that the maker of my controller charged me about $40 for assembly and his expertise above the cost of his parts.  

 

I started casting with no one having to put out fires, restore electrical service or getting electrocuted.  

[tnguy]

TNguy,
 
Mechanically, or digitally, as the case may be, I do not know how to calibrate the digital thermometer linked to above.  It's not covered in my instruction booklet.  However, a known source, regarding temperature, is ice water.  Fill a glass with ice to the brim, fill with water.  In ten minutes the water temp will be exactly 33 degrees f. for about the next 10 minutes.  Insert your thermometer and adjust to 33 degrees.
 
This is a trick that health inspectors used to use to test the calibrations of stem thermometers in restaurants.  But it still works.

That will work to a degree (no pun intended) and you can also use boiling water to get the 100C point. Though it won't tell you your mid-scale deviation. When I worked in a calibration lab, we'd run through a range of temperatures and you'd certify the device as being so-and-so accurate (2% I think) over a certain range.

If you just want to adjust, there will probably be two pots in there you can tweak (assuming it's not done digitally which is possible). Edited January 28, 2014 by tnguy

[tnguy]

If you just want to check the temps, Harbor freight often has those remote thermometers on sale. I use one for checking the temperature of my wife's kiln.

[jaysouth]

The infra red remote sensing thermometers,like the one at Harbor freight, usually don't work too well with molten metals.  Most molten metals like lead form a 'skin' over the top that is not the same temp as the mass of molten metal.

[peejman]

The device that you have linked to is a digital thermometer.  In fact, I have one exactly like it.  However it is not a multimeter and it will not control the current to your pot to maintain a constant temp.  If you buy one of these to measure the temps of your casting process, you will also need a stainless steel probe with K type plug.  The two probes that come with the thermometer are for inserting in ovens, AC ducts, etc.  They will  not survive the molten metal in a casting pot.

 

In the top photo, you can see the coiled cord of the K probe from the  item you linked to.

 

I am pleased with mine, I have used it for a lot more applications than tracking temps in my casting pot.  I just can't figure out how to calibrate it should the need arise.

 

 

Does the pot not have some sort of thermostat, or is it on/off only? 

 

And yes, you'd need a k-type thermocouple to read the high temps.  As for calibration... buy a calibrated TC that comes with an error table.  We have piles of them at work for use in our vacuum furnaces up to 2500 deg F. 

 

http://www.amazon.com/Hanna-Instruments-Waterproof-Thermocouple-Thermometer/dp/B0085X6JA4

[tnguy]

The infra red remote sensing thermometers,like the one at Harbor freight, usually don't work too well with molten metals.  Most molten metals like lead form a 'skin' over the top that is not the same temp as the mass of molten metal.

 

Interesting. I was more thinking in terms of mold temperatures but good point.

[jaysouth]

tnguy, 

 

you rascal!  A trip to harbor freight for me is 40 miles round trip and about a hundred bucks out of my fun fund, just on impluse buys.  Now I have to look for the ads to get a coupon for an IR remote sensing thermometer.  

 

I might as well order one of everything they carry and have it delivered for 6.99.  That will prevent me from putting a couple of thousand miles on the odometer in the next couple of years.

 

Hmmm..................on the other hand, I could just get another PID controller for the hot plate.

[tnguy]

Sadly they are also a long way from me too. I either have to visit Clarksville or one of the *two* very close together on the east side of Nashville.

I think it was around $10 for the one we bought when it was on one of their discount things.

 

Hopefully there will be one on the west side of Nashville sometime.

[jaysouth]

Does the pot not have some sort of thermostat, or is it on/off only? 

 

And yes, you'd need a k-type thermocouple to read the high temps.  As for calibration... buy a calibrated TC that comes with an error table.  We have piles of them at work for use in our vacuum furnaces up to 2500 deg F. 

 

http://www.amazon.com/Hanna-Instruments-Waterproof-Thermocouple-Thermometer/dp/B0085X6JA4

 

The pot has graduated heat setting from 1 to 9.  Using a given setting on the scale will give wide variances as much as 30-40 degrees plus/minus.  When you plug the pot into the PID, set the pot on the highest setting and let the PID control the heat.