PID Controller Questions

[Terryfromok]

Howdy from sunny but cool Oklahoma.

I built a PID controller to use on my Lee Production Pot. I wanted a controller I could plug the pot into. I bought the recommended parts from Auberins plus purchased some others from Radio Shack.

One other item, I am not an electrical savy person. I know how to do somethings, but not everything.

I plugged the unit in and the following has happened:

It powered up and the PID lights up displaying the measured temperature along with the set temperature value.

My question is why the measured temperature displays 167 degrees. The thermocouple is working as when I touch the probe, the indicated temperature increases.

Did I wire up something wrong?

Thanks for all help in advance.

Terryfromok

[Casting Timmy]

is the controller set up for the right style thermocouple? Also make sure you wired it up right as you can't reverse the wires. Type k thermocouples are yellow and red if I remember right and type j are white and red. Either way red is negative.

[Casting Timmy]

Welcome to the group as well

[shaune509]

If reading goes up when holding the probe your polarity is ok. The thermo couple makes a DC micro voltage that changes with temp, that is what the PID is reading and converting to the readout. The calibration or type is mis set as stated above. Does the pid have a calibration setting? if so you may try to set it with ice water for 32/F or0/C.
Shaune509

[theperfessor]

Welcome to the forum. I'm not really an electrical guy but I have built a dual PID unit so allow me to offer a couple of suggestions.

- As suggested, make sure you have the right type thermocouple for your application and controller. Some controllers will take a variety of inputs and may need to be put in the proper mode to recognize the input properly. Different sensors may also be connected to different terminals so make sure you are hooked up to the right connections.

- Make sure that you are using the same type wire all the way from the thermocouple to the PID terminals. Don't put another type of wire or interchange the wires in the circuit. Thermocouples work by the use of dissimilar metals in contact so using any other type of metal wire can cause problems. If you want to put a thermocouple plug in the unit then you should cut enough wire off the end of the thermocouple to run from the socket to the PID controller terminals. This will maintain circuit integrity.

- Read the instructions to become familiar with any error codes, startup/initialization procedures, etc.

- Be sure you're in the right unit system - Fahrenheit or Celsius.

Maybe none of these things apply, just offering suggestions.

[Stampede]

Okay, I produce Industrial Thermocouple sensors for a daily living. The best way to check if you have the system set up correctly and if the sensor is connected the correct way is to hang the sensor freely from any object and see if the display is giving you the correct ambient temperature. The above mentioned wire colors should be correct, but can be different depending where they are produced. Look at my American colleague site of Omega.com http://www.omega.com/techref/thermcolorcodes.html for the correct wiring. I use only Eurotherm PID controllers or my own produced PID controllers . So I can’t tell you what might be wrong. Changing the wire connections will solve the problems sometimes. There should be a + and a – on your PID. Yellow for + and Red for -.

But hang the sensor free from the wall of the melting pot, don’t let it touch it, this is where 99% of all misreadings start. Plus is your sensor “grounded” or “ungrounded”? For in a melting pot you need an ungrounded (or insulated) one. A grounded version will ruin your readings in this situation. The sensor should only touch the lead mixture.

If your sensor and/or wires touch an other metal you have unintentionally created a new thermocouple, than your PID controller is confused about the signal, simple as that.

Peter (Stampede)

[Mal Paso]

- Make sure that you are using the same type wire all the way from the thermocouple to the PID terminals. Don't put another type of wire or interchange the wires in the circuit. Thermocouples work by the use of dissimilar metals in contact so using any other type of metal wire can cause problems. If you want to put a thermocouple plug in the unit then you should cut enough wire off the end of the thermocouple to run from the socket to the PID controller terminals. This will maintain circuit integrity.


+1 and if you use a plug, get one rated for thermocouples like the one Auber sells.

[kitsap]

Terry,

Some good suggestions in the other posts. You can scroll through the various parameter settings for the controller (25 items I think). Compare the values to those in your instruction manual that came with the unit or is available on line from Auber. There is a chance some of your values may not be set at the factory default. Check the type of thermocouple, most likely either K or J. Also there is an input offset that should be at 0 and may have been changed.

I have had one controller out of several that had problems retaining the settings after a power outage and surge and had to be completely reset.

Please report back as to your progress.

DougF

[Terryfromok]

Good morning from Oklahoma!!

Thanks for all the replies. Here are my replies:

It is the "K" type high temperature thermocouple.
It is directly connected to the PID.
The polarity is correct.
The unit system is Fahrenheit.

I have made adjustments with the offset parameter so the PID will indicate 32/F when the thermocouple is inserted into a cup of ice water.

I have made adjustments to the set point to see if the relay will function. It does.

I will have an electronics buddy check it out tomorrow to see where the problem is, if there is one.

[Pigslayer]

My PID was set at 0 degrees centigrade at startup. I left it there & use centigrade conversion as my set temp.. I cast anywhere from 330 centigrade to 355 degrees centigrade depending on the mold. Just gotta play with it. Find a reference point or "bench mark" & go from there.

[popper]

Anybody know of a dual PID controller or one that has 2 thermocouple inputs? I would like to find a unit that will control the pot and readout mould or hot plate temp, both continuously. I could get 2 PID controllers, but that means a bunch of wires on my workbench.

[bigjason6]

Anybody know of a dual PID controller or one that has 2 thermocouple inputs? I would like to find a unit that will control the pot and readout mould or hot plate temp, both continuously. I could get 2 PID controllers, but that means a bunch of wires on my workbench.

Why not build two controllers into one large enclosure?

[theperfessor]

That's what I did. See the sticky in this section. It works fine for controlling hot plate and casting furnace.

[popper]

Will the small Auber unit indicate temperature continuously, or just the larger one? My hot plate is the cast iron top type so it has pretty consistent temperature, just want to monitor it or maybe drill a hole in the mold and monitor that. My re-loading/casting bench is just my garage workbench so I get to set everything up every time. Kind of a PITA, but that's life.

[theperfessor]

I could be wrong but I believe the small single line display unit shows the thermocouple temperature in operation but switches to show the set point temperature when you change it (press the up/down arrows). I don't have one but my BIL does and I'm pretty sure his operates that way. You may even be able to set different display modes.

I use a thermocouple on my molds that requires a 1/4-20 tapped hole to screw into. Others drill a deep enough hole to use a probe type. Easier to remove the latter, but I have been casting with the thermocouple attached throughout the casting session so I can continuously monitor mold temp. I refill the mold at the same temperature every time. Seems to help consistency a little. It's interesting to watch the temperature go up and down as you fill the mold, and to watch the effect the size of the sprue puddle has on temperature change and cycle time.