Pid/timer conundrum

[Redjello]

Im trying to wire my inkbird ITC-106 VH to a timer DH48S. This type of timer gets manually set then repeats this time when the unit receives power. I cannot seem to find a way to wire ir based on my needs. I want to set the Temperature on the PID @ 170f to turn on my ssr's that power my 2 heating elements. This function is basic and works as it should. My problem is that I want the pid high alarm to trigger the timer on @ 170 which also works as it should, which starts the manually set time of 12 hours. This also works. But I need the timer, after it's done at 12 hours to either turn of the elements or the pid and end the brew. Then if I want to do it again I somehow turn on, reboot the system so it repeats this same process.

The pid has a NC and NO relay for the alarm. And so does the timer. I cannot logically figure out how to get all relays to do what I want. Does anybody have any experience with such a sequence? I would appreciate any input. The only thing I can think of is that I'm missing a component that not familiar with. The pid and timer are using 240v and I have the elements wired first through mechanical contractors so I can manually turn one of with a switch is I need to.

 

[doug293cz]

170°F for 12 hours? Doesn't sound like any brewing process I know. What are you trying to accomplish?

What is the step by step process sequence that you wish to automate?

Can you post a schematic or wiring diagram of what you currently have?

Brew on

 

[Redjello]

I want to set a specific set point on the pid. When temperature is reached, the timer kicks on by way of pid alarm relay. When time is over, I want the system to turn off.

 

[doug293cz]

Seems simple enough. What is the exact model number (all characters) of your timer? There are several variations.

How things get wired depends on what other elements you have in the control box, which is why I asked for a wiring diagram.

For what it's worth, the DSPR controllers (but not the DSPR1) from Auber Instruments have the functionality you want built in.

Brew on

 

[Redjello]

Thank you. I have the auber SWA-2451B, and yes this does the job. But the reason I want the the separate timer and pid, is because it is super simplistic. Pid heats to set point, then triggers the alarm that starts timer, then system turns off after the time is done. When the panel is on, the sequence is set and automatically turns, so it's fool proof for employees. The time is visible and can be changed manually by the mechanical buttons. I have the Peds alarm triggering the start of the timer. But I don't understand how I can then after the time is over, have something somehow turn off the entire system, the, pid, or the mechanical contractors that the elements are on. Any of those would work. Here is the wiring diagram for the timer.

 

[Redjello]

Here's the diagram of how it currently have it wired up. Notice that the output of the timer is open and not connected to anything. Because this is where I'm having the issue with wanting to whole system to shut off. As it is wired currently the PID alarm does trigger the timer. But after the time is over nothing happens because obviously I don't know how to finish the sequence of relay connections to make that happen. I included the timers diagram printed on the case. FYI the timer has a reset terminal and a pause terminal that I attempted to incorporate to possibly get the function I'm after.

 

[doug293cz]

Ok, I know a way to do what you want, but it requires adding another contactor to the system. Are you OK with that?

Brew on

 

[Redjello]

Omg, yes. I'll add whatever it takes

 

[doug293cz]

Ok, I'll sketch something up. The extra contactor can either control total system power, or just power to the control elements (PID, timer, contactor coils, etc.) Do you have a preference?

Brew on

 

[doug293cz]

Forgot to post the previous when I wrote it, but I have completed a first design that I think will do what you want. Let me know if you have any questions.

Brew on

 

[Redjello]

Wow thank you! I'm still trying to understand it though. The total system power is ideal to control with the extra contactor. Are the pids 11 and 12 reversed mistakenly? And I see the timers 7 and 8 are not jumped, but they eventually jump when the pid alarm triggers? On the timer, 5 is what triggers the system contactor to turn off, but I see that it is spliced together with line 1 power of that first contactor. I don't understand how that can control the contactor if that line 1 power is supplying constant power to that contactor. Are the drawings circled in blue manual switches or contactor/relays? Please excuse my ignorance on your super professional and beautiful drawings. And thank you once again.

 

[doug293cz]

Yes the switches highlighted by the blue outlines are manual switches. It is critical that the two on the left are momentary contact.

The NO momentary contact switch turns everything on by applying power to the main power contactor coil. Once the main contactor is on, it is latched on by power flowing thru the contactor, and then thru the NC contact pair in the timer (from terminal 8 to terminal 5), so the start switch can then be released, and power stays on. Since the timer in unpowered when the system is turned on, the NC contact pair in the timer remains closed.

Also, when the main power is turned on, the PID will start sending power to the element (if the element enable switch and contactor are on.) Once the process temp is reached, the NO alarm contacts in the PID close, applying power to the timer, thus starting the timing function. The NC contacts in the timer remain closed when power is applied because the time has not run out.

When the timer times out, the NC contact pair in the timer opens, and power is removed from the main power contactor coil, causing main power to be shut off, and the system goes cold.

The NC momentary contact switch provides a manual way to shut off the system, should that be necessary for any reason.

The PID alarm terminals are wired correctly. #12 is the alarm common, and that is normally where incoming power to the relay is applied. #11 is the NO contact that pairs with #12, so that is where the alarm "load" (the timer) power is connected. #12 gets connected to #11, when the alarm triggers.

One potential problem with this circuit is what happens to the PID alarm output if the process temp falls below the alarm trigger point. If the alarm shuts off for a temp undershoot, then power to the timer goes off until the temp goes back above the alarm level, which restarts, but also resets, the timer. Possible solutions to this problem are a hysteresis setting for the alarm so that it doesn't shut off on a temporary undershoot, or setting the alarm trigger point a few degrees below the process set point (lower than any normal process oscillation.)

EDIT: According to the ITC-106 manual, there is a hysteresis setting for the alarm output, so this will need to be set correctly.

Finally, your timer (per the pic you posted) is a DH48S-2Z, it has two SPDT output relays, but no pause or reset inputs.

I'll be gone till evening, so any additional questions will have to wait until then.

Brew on

 

[Bobby_M]

Seriously man, just get the Auber DSPR120. It does EXACTLY what you want to do with just one module.

Front screen temperature setpoint 170F
t= 12 hours
tsp=170
ALH=170
EO=Off

Fan of Rube Goldberg perhaps?

 

[doug293cz]

Seriously man, just get the Auber DSPR120. It does EXACTLY what you want to do with just one module.

Front screen temperature setpoint 170F
t= 12 hours
tsp=170
ALH=170
EO=Off

View attachment 815212



Fan of Rube Goldberg perhaps?

We sort of covered this already. OP wants operators to have a fool proof way to run a process. The only thing the ops should be able to adjust is the process time. Being able to do this without having to navigate a controller's settings menu is one of the design goals (I surmise from previous postings.) So, the OP wants something where the ops don't have to mess with a PID/DSPR setting menu, and the DH48S timer provides that capability.

@Redjello , feel free to correct me if I have misinterpreted the design goals.

Brew on

 

[Redjello]

Yeah, I hear you about the Auber. Tomorrow I will run Doug's schematic and I'll report back. But yes, Rube Goldberg much? The idea was to idiot proof it, so thank you Doug for your help. Are you an engineer by trade?

 

[doug293cz]

thank you Doug for your help. Are you an engineer by trade?

Yes, retired now. This kind of thing helps me keep my mind sharp.

Brew on