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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!
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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