PID placement of sensor

[Mike W1]

I'm thinking a lot of folks are confusing dual temperature displays with dual input unit's which apparently exist but at a much higher price range than the one's the majority of bullet casters use. One of the stickies is about a dual setup to control a lead pot and some other separate piece of gear. He used the Auber SLY-2352 controller. That would be 2@ of both the PID and the TC's. A separate input (TC) for each controller and controlling 2 different apparatus'. Within a matter of seconds the temperature in a casting pots lead is going to be about the same throughout the mix/alloy. Lead conducts heat very rapidly. I've had a probe in 1/2" off the bottom and another 1/2" below the top and the difference between the 2 is negligible if any.
You just aren't going to have a pot of lead at 2 different temperatures and regulate our pots that only plug into one power source. Just can't happen.

[Dapaki]

Actually, that is what the dual temperature, process and strain PID controller does, it has AI (limited) to determine the difference between the two temperatures and pulse the SSR to keep the difference the same. Think of the dead band in a PID, it 'anticipates' the temperature as it approaches the set point, pulses the SSR to match the setting desired from both probes. Yes, you have to program in the dead band to match the normalized difference between the two probes but in the end, you get a stable temperature (if you keep within the heating elements capabilities) throughout the container.

Yes, it's overkill, yes it's tedious, yes its expensive but we are tinkerers above all, are we not?

[Mike W1]

Actually, that is what the dual temperature, process and strain PID controller does, it has AI (limited) to determine the difference between the two temperatures and pulse the SSR to keep the difference the same. Think of the dead band in a PID, it 'anticipates' the temperature as it approaches the set point, pulses the SSR to match the setting desired from both probes. Yes, you have to program in the dead band to match the normalized difference between the two probes but in the end, you get a stable temperature (if you keep within the heating elements capabilities) throughout the container.

Yes, it's overkill, yes it's tedious, yes its expensive but we are tinkerers above all, are we not?

Well Sir you're far more knowledgeable on PID's than I am for sure. I run 4 different PID's on 4 different setups. They all keep things with a couple degrees of set temperature. There is no reason I can see for me to require anything better than that. Mostly I like the repeatability. Turn things on and give it 20 minutes to heat up and I'm there. Molds are hot, ingots are hot and the lead where I want it. A $150 PID might gain a couple degrees more accuracy than a $12 Rex but I think it would be wasted money & time.

[Dapaki]

Well Sir you're far more knowledgeable on PID's than I am for sure. I run 4 different PID's on 4 different setups. They all keep things with a couple degrees of set temperature. There is no reason I can see for me to require anything better than that. Mostly I like the repeatability. Turn things on and give it 20 minutes to heat up and I'm there. Molds are hot, ingots are hot and the lead where I want it. A $150 PID might gain a couple degrees more accuracy than a $12 Rex but I think it would be wasted money & time.

Indeed! I think that people get the wrong idea some times when someone jumps in the conversation and says, "What about.... xxxxx?". Primarily I was just responding to the PID use and the disparity I am seeing in temps from inside the pot to the nozzle temp outside the pot. I am not going to spend big bucks on a fancy PID either but it is fun to brainstorm ans speculate, right?

I have a box of these things (pulls from old jobs) and it would would be interesting to see what probe locations work best for the dual temp system.

[RydForLyf]

Indeed! I think that people get the wrong idea some times when someone jumps in the conversation and says, "What about.... xxxxx?". Primarily I was just responding to the PID use and the disparity I am seeing in temps from inside the pot to the nozzle temp outside the pot. I am not going to spend big bucks on a fancy PID either but it is fun to brainstorm ans speculate, right?

I have a box of these things (pulls from old jobs) and it would would be interesting to see what probe locations work best for the dual temp system.

To be honest, all we want the PID to do is maintain the temperature of the lead at a specific temperature and eliminate the monkeying around with a physical knob and having to read a thermometer for reference. We could measure the temperature in Fahrenheit, Celsius, Pink Flamingos, or any other analog scale as long as it is repeatable. I don’t know about you, but as long as my lead can stay about 3.5 Pink Flamingos and fill the mold, 3.5 Pink Flamingos is where I’m going to set it next time. I don’t care what temp the outside of the pot is, how the temperature of the spout cools off when I’m not casting and how quickly it heats up when I start casting, all I need to know is that I’m at 3.5 Pink Flamingos and the pot is full. If your situation is different and 3.5 Pink Flamingos won’t work for you and you like 76 Fuzzy Squirrels, then 76 Fuzzy Squirrels it is for you. My Pink Flamingos won’t care.

[bazzer485]

To be honest, all we want the PID to do is maintain the temperature of the lead at a specific temperature and eliminate the monkeying around with a physical knob and having to read a thermometer for reference. We could measure the temperature in Fahrenheit, Celsius, Pink Flamingos, or any other analog scale as long as it is repeatable. I don’t know about you, but as long as my lead can stay about 3.5 Pink Flamingos and fill the mold, 3.5 Pink Flamingos is where I’m going to set it next time. I don’t care what temp the outside of the pot is, how the temperature of the spout cools off when I’m not casting and how quickly it heats up when I start casting, all I need to know is that I’m at 3.5 Pink Flamingos and the pot is full.

As the op I was just pointing out that the spout , nozzle if you like, varies considerably on the number of pink flamingos when casting and in fact the lead temperature was a pink flamingo hotter that the nozzle.
Cheers
Barry

[jsizemore]

I use my PID for other uses as well. My thermocouple has a plug on the other end. Each thermocouple is hard mounted to whatever appliance it goes with, whether it be my second pot, mold oven, or powder coat oven.

I started to do that but all thermocouples are not created equal and didn't want to go through the calibration thing every time I swapped. I've got a separate PID for lube/sizing, Hitek coating and casting. PID's are cheap enough.

[RydForLyf]

As the op I was just pointing out that the spout , nozzle if you like, varies considerably on the number of pink flamingos when casting and in fact the lead temperature was a pink flamingo hotter that the nozzle.
Cheers
Barry

And you expected this thread to stay on topic? I’ll see your Pink Flamingo and raise you two Fuzzy Squirrels.

[bazzer485]

No, I think this thread has reached its end! So any flamingos and fuzzy wizzuy’s is welcome as far as I’m concerned ! Flamingo away.

[Tazlaw]

Two turtle doves, and a partridge in a pear treeeeee!

[Mal Paso]

Anyone who has seen the movie Pink Flamingos should know, any calibrating in Pink Flamingos should be done in The Pit.

[Tazlaw]

Semi seriously—I just ordered my my first PID’s from amazon. One was $11, and the other $8. Including shipping. I also ordered two TC’s, one bare and one to go into pot. It would be nice to be able to put the bare one outside the pot somewhere (consistent) and not have it being in the way while casting.

As far as brain-storming, what about tying the Thermocouple to the rod going down into the lead? This would make it less in the way wouldn’t it? This would have to be a probe TC and tied with steel wire.

[bazzer485]

Taz, I’ve just ordered ten TC’s with plugs on the ends for about $10 including postage from corana virus land.
Baz

[Tazlaw]

Taz, I’ve just ordered ten TC’s with plugs on the ends for about $10 including postage from corana virus land.
Baz

Each or a dollar a piece? What service did you use? Amazon, Wish, eBay....?

Oh, and my PIDs came with an SSR and TC, but I ordered two longer TC’s.

[bazzer485]

Tax, eBay has changed its format and I can’t find a way to copy the url of the listing. It’s for five, not ten, k type thermocouples for $5.85 with free postage via speedpak from HongKong I believe. There are several other similar listings if you search
Baz

[Drew P]

People often make this way more complicated than it can be. Combine these two items with a 1/4” hole in the center bottom of the pot and enjoy stable, reliable, durable readings. Any other method I’ve seen was a compromise to what I’ve seen on my pot using this way. Keep in mind that heavy lead bars will bang into this, and stirring rods and scrapers etc. don’t put janky wires into your pot if you don’t have to. Okay, carry on.

[bazzer485]

People often make this way more complicated than it can be. Combine these two items with a 1/4” hole in the center bottom of the pot and enjoy stable, reliable, durable readings. Any other method I’ve seen was a compromise to what I’ve seen on my pot using this way. Okay, carry on.

Did you use any kind of washer?

[RydForLyf]

People often make this way more complicated than it can be. Combine these two items with a 1/4” hole in the center bottom of the pot and enjoy stable, reliable, durable readings. Any other method I’ve seen was a compromise to what I’ve seen on my pot using this way. Keep in mind that heavy lead bars will bang into this, and stirring rods and scrapers etc. don’t put janky wires into your pot if you don’t have to. Okay, carry on.

That sure is a slick way of mounting the TC, but I think the heavy nut will put a significant time lag in the temperature reading and result in temperature swings that you are trying to avoid.

The thermocouple is designed to respond quickly to temperature changes and in this scenario, it isn’t contacting the lead, but is measuring the air temperature inside the nut. It would be interesting to put a wet probe in the lead to observe lead temps being controlled by the acorn nut PID. I do think that is a great idea to seal it out, it fear the response and performance will be muted.

[hermans]

That sure is a slick way of mounting the TC, but I think the heavy nut will put a significant time lag in the temperature reading and result in temperature swings that you are trying to avoid.

The thermocouple is designed to respond quickly to temperature changes and in this scenario, it isn’t contacting the lead, but is measuring the air temperature inside the nut. It would be interesting to put a wet probe in the lead to observe lead temps being controlled by the acorn nut PID. I do think that is a great idea to seal it out, it fear the response and performance will be muted.

Very interesting....always wondered how/where in my ProMelt I can mount the sensor, but I sure am hesitant to drill a hole in the stainless steel wall of my beloved ProMelt

[lightman]

I replaced one of the bolts on the top of my ProMelt with a longer bolt and a jam nut that holds a piece of flat bar stock thats drilled to hold the probe. The jam nut allows me to remove the probe and swing the bar out of the way when fluxing and stirring. The probe hangs in the molten lead about 3/4 inch from the edge of the pot.

I welded a similar piece of bar stock to the side of my smelting pot to hold a probe or thermometer.

Sorry, no fuzzy squirrels or pink flamingos here!