Pid

[BattleRife]

...realized I still have to cut the hole at the front for the TC socket which I'm still waiting on to be delivered sometime between Dec 16th and Jan 6th!!!

Are you talking about one of these?


I can mail you one, I have dozens. You'll have it a lot sooner than Jan 6th. And you can see the dimensions if you want to get started cutting a hole.

[dearslayer]

Are you talking about one of these?


I can mail you one, I have dozens. You'll have it a lot sooner than Jan 6th. And you can see the dimensions if you want to get started cutting a hole.

Yes that's exactly what I'm waiting on.

[dearslayer]

I do ship worldwide but typically its not cost effective as shipping is very costly outside the states.


On thermocouple hook up.

You have two wires. Typically a they have a red and a blue connector on them and they also have the same color stripes on them as well.
On the PID you will have a - sign and a + sign under thermocouple connection.

The red connector goes to the + sign and the blue goes to the - sign.
Don't worry about this too much as it will not damage the unit if hooked up incorrectly.
What till happen is that it will read the temp backwards.
So typically you turn on the power to the PID.
The temp will read ambient. Grab the probe with your hand and hold it for a few mins.
The temp should go up slowly. If it goes down then most likely you have the wires hooked up backwards.

On fuses, to be totally honest I stopped using them in my builds.
I know this will get a lot of responses so I will explain.
The device you are controlling typically plugs into a standard 120v outlet.
The majority of those are controlled by a 15 amp circuit breaker in your electrical panel.
Having a 15 amp fuse is redundant and not needed.

The typical casting furnace (lee 4-20) pulls around 7 amps and it isn't fused so if you wanted to a 10 amp fuse would be a good safe measure but as I mentioned no needed.


The units I build have the following parts (for reference)

Golander 1/32 PID
Golander 25 amp SSR
8 ft or 10 ft extension cord
Car Alarm toggle switch - I only switch the PID power not the entire load.
150mm x 105mm x 55mm Enclosure
100mm K thermocouple probe with 3m cable

I don't use a heatsink because the SSR is mounted on a metal enclosure. I haven't had any issues.
I rate the units for 15 amps even though the SSR is 25.

Anyone that builds their own PID only needs to switch the power to the PID controller itself.
I do not recommend switching the entire load (pot or oven).
If the PID doesn't have power then the SSR will not have power either.
Which means no output.
In the crazy event that the SSR fails closed (in other words power is stuck on) then you can just unplug it.
I have been dealing with controls for over 25 years and have NEVER seen a SSR get stock on. I have seen plenty that either didn't pass voltage or passed a reduce amount of voltage.

If anyone has any build questions please send me a message and I will help you.

Thanks for all this info. Im sure I'll have a bunch of questions once I get into it.

[dearslayer]

Actually the +/- symbol is on the left side last 2 connections ( 4&5 ) on the bottom but it says for the SSR. Where I currently have the TC wire connected ( at 6&7 ) it says "AL W1".

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[HATCH]

You have it hooked up incorrectly.

9&10

Notice it say TC
Also notice the small + and - sign

Sorry for the edits. Have to look at the picture

10 is + or red connector
9 is - or blue connector

Be more thing and it might not be a huge issue but the PID you have is good up to 752 F

Notice the 400c under range


The alarm is a contact closure. When the PID hits a preset temp it closes the alarm contacts

[dearslayer]

You have it hooked up incorrectly.

9&10

Notice it say TC
Also notice the small + and - sign

Sorry for the edits. Have to look at the picture

10 is + or red connector
9 is - or blue connector

Be more thing and it might not be a huge issue but the PID you have is good up to 752 F

Notice the 400c under range


The alarm is a contact closure. When the PID hits a preset temp it closes the alarm contacts

Aw gotcha. Good catch on the hook up. I did not realize the Max temp on the unit. Hopefully if I need to replace it the size of the unit will be the same at least. Can you recommend a proper one ...should I need it?

[HATCH]

I normally cast at 750 f max so most likely you will be fine.
The size of the unit is 1/16 DIN
It is a standard size that the majority of PID manufacturers use.
I use 1/32 because I like the more compactness.
Plus the fact the smaller the enclosure the cheaper it is.

During COVID lockdown I made some setups that used a plastic enclosure because that is all I could get.
I haven’t had any complaints and if a customer did have a issue with their plastic enclosure I would just swap them out with a metal unit at no charge besides their shipping cost to me.

[SteveM54]

Printed out this article & added it to the read pile.
The amount of info on this subject along is unbelievable.

[David2011]

Hatch, would you mind sharing what enclosure you use?

[HATCH]

It’s secret.
Haha

150mm x 105mm x 55mm
Aluminum not the plastic ones
You can search eBay and pick them up for around $20 shipped
Takes a while to get here.
I purchased a custom 1/32 DIN knockout punch to cut the PID cut outs.
Requires a single round hole drilled in the middle where you want to knockout to be.

I don’t buy them off of eBay but it should point you in the right direction.

Keep in mind I use 1/32 sized PID controllers.
If your gonna use a 1/16 like this poster used then you need a much larger enclosure


Charles

[David2011]

Thanks. I like the looks of yours and will probably go with the 1/32 size. I like doing new kinds of projects; going to give this a shot.

[HATCH]

If you have any questions just shoot me a PM and I will help you.

[dearslayer]

Well I finally got this thing assembled and wired. Flipped the switch and there was no magic smoke so that's a good start. Just have to figure out how to program the darn thing. The instructions leave a little to be desired!

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[Noah Zark]

OK, ignorance on full display - what's a PID?

I realize it's been weeks since asked, but PID is the type of digital controller used in controlling lead melt pot temp accurately. It stands for Proportional-Integral-Derivative control functions, and industrial process controllers since the 1930s on contained these functions, starting with pneumatic controllers/circle chart recorders which can be seen in old movies and photos of control rooms.

Controllers work by constantly measuring the difference between a setpoint and the measured and controlled process variable, called the "error" - like your home thermostat does, and sending an output based on the error, to the control element that affects the process - your furnace or boiler oil burner, or gas valve.

The proportional function acts in proportion to the amount of error; small error, little proportional effect. Large error, lots of proportional effect. Problem is, proportional control alone can and often ends up with ever-increasing error if too much proportional effect or "gain" is employed. A chart recorder measuring a system with too much proportional gain looks like a lie detector chart - wild swinging.

Enter the integral function. It looks at the error over time in the past and integrates the rate of change of the error value. It's purpose is to say "Whoa, hoss!" to the proportional function if it gets too carried away.

If the integral function is backward-looking, the derivative function is the forward-looking predictive function that tries to predict the change in the error, and anticipate the needed effect on the control signal to further reduce error and provide even more stable control to the system - so that the chart recorder pen draws a thin, steady line right on setpoint instead of painting a wide swath of ink somewhere above and below setpoint.

Going back to the home thermostat, there's a tiny resistor that gives off heat to the bimetallic spring proportionately to the current drawn by the gas solenoid valve coil. This resistor preheats the thermostat spring in anticipation of room temperature reaching setpoint, and causing the mercury switch to tilt open and close the gas valve early so that room temperature doesn't overshoot too high - that's how the derivative function works; it "looks ahead" at how much error there is and which way it's headed, and says, "that's enough right there, lads" and halts control output for the time being until the error between setpoint and measured variable (either room or lead temp) grows again.

With today's inexpensive, programmable digital controllers such as those pictured in this thread, one can adjust the gain in each of the P-I-D functions manually to reduce control error and improve process stability, or one can select the "autotune" feature which enables the controller's internal computer to set its own P-I-D gain settings automatically. Usually "autotune" is enabled two or more times to "tighten" the control function, and the result is usually improved process variable control each time, to a limit. There are exceptions to autotuning some systems, but to someone like me who cut his teeth on Fisher and Foxboro pneumatic controllers with 24h circle charts in a process industry in the 1970s and 80s, these 1/32 and 1/16 DIN digital process controllers are nothing short of black magic.

HTH,

Noah

[oley55]

Noah, thanks for a well written and refined description of the magic of PIDs that dummies like me can understand.

[TjB101]

Well I finally got this thing assembled and wired. Flipped the switch and there was no magic smoke so that's a good start. Just have to figure out how to program the darn thing. The instructions leave a little to be desired!

Really nice looking. I did the autotune once and basically forget everything else I read. Cranked the pot to setting 8, loaded the pot with lead, flipped it on and set autotune. It melted and tested for close to an hour before autotune went off. Pot is set to 720, overshoots every so often to 730.

How are you going to attach your probe to the pot? I didn’t see a mounting screw on yours

[dearslayer]

Currently only have a wire mounted that the probe drops down into but I don't like it because it's not sturdy enough to keep the probe straight down in the pot. The curly wire on the probe has too much tension wanting to pull it constantly. I want a different probe and the I will mount a proper solid bracket.

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[dearslayer]

I also want to get the Lee 4-20 pot soon. This one isn't big enough.

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[dearslayer]

Delete

[dearslayer]

Not sure if this probe is suitable.

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