PID temperature controller?

[BottleFed70]

How hard are these to setup/use? I've seen a few on Ebay but the whole PID concept is new to me. Will I be able to figure it out by studying the manual? I'm fairly good with electrical stuff, but I'm no expert by any means.

Thanks!

[CarWiz]

Originally Posted by BottleFed70

How hard are these to setup/use? I've seen a few on Ebay but the whole PID concept is new to me. Will I be able to figure it out by studying the manual? I'm fairly good with electrical stuff, but I'm no expert by any means.

Thanks!

The PID concept itself is pretty complicated but most controllers make it easy to set up and some have an auto function. As far as the manual, you'll need to be good at translating Chinglish but you should be able to set up the controller without much fuss. Ask about the manual before buying. Most Ebay sellers don't provide one but they are available online. I have a "translated" version of the TET-612 manual if you need one.

[Revonitas]

Originally Posted by BottleFed70

How hard are these to setup/use? I've seen a few on Ebay but the whole PID concept is new to me. Will I be able to figure it out by studying the manual? I'm fairly good with electrical stuff, but I'm no expert by any means.

Thanks!

Gentleman,

I have yet to purchase yet from Caswell products, however I probably will
soon since I am restoring two old motorcycles.

I spotted the questions and comments with regard to PID and ssr's and with 25 years experience in temperature controllers I felt that some of the readers here may benefit from my comments.

First, a short and hopefully clear description of the differences between an SSR and a PID temperature controller. SSR means Single Switch Relay. This is the most simple type of temerature controller. Really , it is not much different than the light switch on your wall, When you ask an SSR temperature controller for a temperature higher than what you are monitoring, it will close a set of contacts on the back of the controller, and pass voltage thru the contacts, this voltage may be 24v, 110v, 120v, 220v, 600v. The contacts are simpley a bridge that closes to pass the volatage on to whatever device is to respond. Do not confuse this voltage with the voltage that actually operates the controller. Since, in most cases the Caswell systems are probably purchased by happy hobbyists/home owners,
I recommend that you purchase controllers that operate on standard 120v ac. Also, whatever you wish to operate on demand of the controller should also be 120v. If you are using a contactor, be sure to purchase one that has a 120v coil. If you purchase a contactor with a 24volt coil, you will need a transformer. This is silly , and unneccessary.

As for the PID controller. The PID controller is considered a step up from an
SSR because it attempts to flatten out the peaks and valleys that you typically get with an SSR. The SSR is an on/off controller, and by nature will give the end user peaks and valleys. The PID controller remmembers overshoot and undershoot and attempts to flatten out the peaks and valleys and to maintain a more stable temperature. Unfortunately, the PID controller is also not one that I would recommend for this process. Typically the PID type of controller is more appropriate for a lenghty process that allows the PID controller to remember and record many cycles until it finally flattens out the peaks and valleys (Hysteresis)

The one thing the SSR and PID controllers have in common is that they both
operate by opening and closing a set of contacts. That is to say they both
produce an "on/off" signal.

For those want a more dependable and long term solution, the answer is to
use a temperature controller which produces an output that has a modulating current. There are many manufacturers to choose from, but my best recommendation is Omron. They are available at your local Graingers

Temperature controller stock number 3mm67 approx $ 190
Output board stock number 3kp45 approx $ 80
Sensor. ask for j-type thermocouple


Since I have yet to set up my own system yet for the Caswell product, these recomendations should be considered preliminary. When I have my system in operation, I will pass on whatever changes/adjustments I made in the system. Anyone wishing to discuss this matter may feel free to call my cell phone 302 898-1658

Eddie

[CarWiz]

I think there's a misunderstanding of terms. When one compares Contactors to SSRs, the SSR stands for Solid State Relay. I've never heard of someone comparing an SSR to a PID Controller. The two have nothing to compare. The PID controls when the internal relays or SSRs are under power using the parameters stored. The SSR is simply an electronic relay to turn the heating elements on. It replaces a contactor/relay. Both need power to switch.

To eliminate any confusion on this board, I suggest we maintain that SSR stands for Solid State Relay as most are accustomed.

[BottleFed70]

Yes, thanks... I've never heard of an SSR controller before (other than a controller that's ment to drive a SSR).

I think I will give the PID controller a try. I did notice that some of them have an auto-learn feature listed in the specifications... so in your opinion it's a useful feature to have as it makes the setup on the PID controller easier?

Thanks.

[CarWiz]

Yes, the Auto function is good. When the system is powered up, let the heaters run until the desired temp is reached. Select Auto at that point. The PID parameters are then set based on heat/time differentials. Some presetting is necessary to let the controller know what hardware you're using. (relays, SSR, thermocouple type, temp display, etc.)

[Revonitas]

Originally Posted by CarWiz

I think there's a misunderstanding of terms. When one compares Contactors to SSRs, the SSR stands for Solid State Relay. I've never heard of someone comparing an SSR to a PID Controller. The two have nothing to compare. The PID controls when the internal relays or SSRs are under power using the parameters stored. The SSR is simply an electronic relay to turn the heating elements on. It replaces a contactor/relay. Both need power to switch.

To eliminate any confusion on this board, I suggest we maintain that SSR stands for Solid State Relay as most are accustomed.

My response was based on some one's comment regarding a PID controller.
Tecnicians who deal with accurate temperature controls generally speak of simple "on/off" controllers as those beiing SSR-single switch relay. This refers to the method of control, regardless of whether or not the controller is solid state, tube or otherwise. The PID type controller seeks to flatten out the peaks and valleys caused by SSR type relays. At this end I am referring to types of controllers which would give the end user the best kind of temperature accuracy, which is neither the SSR or the PID, but one that produces a current output such as 40 millivolt or 4-20ma.

Eddie

[CarWiz]

I don't doubt your involvement. I was concerned that your new interjections would confuse the general readers of this board. Not that we're idiots but few lab technicians gain there info from this site.

At this end I am referring to types of controllers which would give the end user the best kind of temperature accuracy, which is neither the SSR or the PID, but one that produces a current output such as 40 millivolt or 4-20ma.

As far as current output, again you are comparing apples to oranges. My PID controllers DO output current in the range you noted. One port is used to drive the solid state relays and the other port can be used to drive P10, P100 or Cu50 sensors. I choose to use the type K sensors because of the higher range available. (Besides, it came free with the PID.) I think the accuracy of 0.2% for a PID controller is good enough for most of the applications covered on this board and then some. For the range used in powder coating, that amounts to less than one degree (0.8 degrees F). And you can get that accuracy for $50 or less!

If you use a higher range of temps as I do on one oven, the sensor coefficient can be changed to gain +/- one degree accuracy at 1700*F. I figure that's close enough for my stuff. A PID temperature controller is far more than just a switch as you imply. It's a full blown computer that teaches itself and acts based on parameters supplied by the user and/or from what it learned. After re-reading your comments, I'm beginning to doubt whether you even know what a PID temperature controller is or how it works. I let the SSR slide. But of course, I may just be an idiot.