Author Topic: Vacuum Kiln (Read 18323 times)

Den Socling · « **Reply #20 on:** February 18, 2004, 04:34:20 pm »

You might use one Partlow to switch back and forth from heating to vacuum. A second Partlow would be useful in holding the heating water temperature where it belonged.

A third Partlow wouldn't be needed for the vac cycle but a third Partlow with a pressure transducer could tell you where the pressure was.

I'm not sure where that price came from but it sounds a little low.

Den Socling · « **Reply #21 on:** February 18, 2004, 04:41:42 pm »

The Partlow's output would set off a chain of events. They could all be done with relays. Some relays would be time delay relays (TDR's). This is where a PLC could look better but you would need to write the ladder logic that would set the relay output. A PLC is a programmable bank of relays.

Jason_WI · « **Reply #22 on:** February 18, 2004, 04:52:50 pm »

Quote

Jason (where is he?) would say to use a PLC and build your own circuit and software.

Not a PLC but a PIC microcontroller.

Jason

Den Socling · « **Reply #23 on:** February 18, 2004, 04:55:35 pm »

Not defined as a 'PLC'?
Just an itbity one?

shopteacher · « **Reply #24 on:** February 18, 2004, 05:28:43 pm »

Den, I got that price from TTI, Inc.

http://partlow.ttistore.com/

What is the price range of the PLC that would be reqired to operate this kiln?

Jason how much trouble would it be to come up with a working PLC for this application?

Jason_WI · « **Reply #25 on:** February 18, 2004, 11:19:01 pm »

A PIC 16F877 is 8 bux and can do anythin you program it to do. It has 10 bit A/D converter, 30+ I/O pins, and 8 k of program space.

You will need contactor's, signal conditioners for the RTD or thermalcouples, pressure transducer, pumps, and solnoid valves that will be the major cost here.

To control temperature with a band gap or dead band is fairly easy in BASIC, which is what I use to program PIC's with. Here is an example for a PIC:

Upper_limit VAR word
Lower_limit VAR word
Upper_limit = 1020 ‘102 degrees in 1/10ths
Lower_limit = 1010 '101 degrees in 1/10ths

Control:
IF Temp > Upper_limit THEN OFF ' Over upper limit then Heat OFF

IF Temp < Lower_limit THEN ON ' Under lower limit then Heat ON
RETURN ' return leaving heat in last state

OFF:
Out8 = 0 ' Heater Off
MMFlag = 1
RETURN

ON: ' Heater On
Out8 = 1
RETURN

This is what the output would look like:

This has been simplified greatly but as you can see it is fairly straight forward.

The output would have a 2N3904 transistor to drive a 12 volt relay or can directly drive a solid state relay with a series current limiting resistor of 220 to 330 ohm.

Jason

shopteacher · « **Reply #26 on:** February 19, 2004, 02:57:43 am »

Jason, would one PIC be capable of running the different selnoid valves, pumps vac & water, fans and monitor the RTD and pressure transducer?
What would it cost to build the unit and program it?

Den Socling · « **Reply #27 on:** February 19, 2004, 04:47:43 am »

Shopteacher,

I checked TTI. The base list price of the 1160 is $191. This is with one SPDT relay. However, you ususally find more jobs for the Partlow and need to add outputs. Additional relays cost $27 each and linear (current) outputs cost $48 each. Another option is the RS485 interface board for $64. This allows the Partlow to be connected to a computer.

Den

Den Socling · « **Reply #28 on:** February 19, 2004, 06:32:15 am »

Looked at TTI again and noticed something else. The new 1160's are called 1160 plus. Output one is removable so they can be sold with no output. Their price doesn't include any output.

shopteacher · « **Reply #29 on:** February 19, 2004, 07:55:32 am »

Glad you looked into it Den. I'm not very knowledgeable when it comes to electronics and sure do appreciate your input on this.
How would connecting it to the computer help? Old computers are a dime a dozen nowdays. I've seen dozens go to the dumpster. Would be nice if there was a way to make use of an outdated computer to control the kiln.

Buzz-sawyer · « **Reply #30 on:** February 19, 2004, 08:34:38 am »

Teacher...
It sure can be done...years ago I worked in a control room using a 200 pentium processor to run and control an entire processing plant includind a wide variety of sensors solenoids motors ....you name it! the soft ware for commercial applications could probably be had free if I knew who still cared or had it!

ronwood · « **Reply #31 on:** February 19, 2004, 09:33:29 am »

shopteacher

I think using a PC would be a great idea. If we could find some PC card that would have the right interfaces you might be able to do it fairly reasonable. If I get a chance I will look around tonight on ebay and other sites to see if I can find some used cards. New cards may be to expense.

I would even consider writing the program that would run the kiln. Writing software for the credit card industry so I do have a lot of realtime software development.

One thing that would need to be address if using a PC is the enviroment that you would have it in. It would need to be somewhere were it does not get to hot.

Ron

shopteacher · « **Reply #32 on:** February 19, 2004, 10:06:32 am »

Buzz Sawyer : Any and all help is welcomed and appreciated. I come in contact with some industrial boards and computer main frame hardware through a salvage company I'm friends with, but have no idea what the boards are or their use. if you can tell what to look for I'll keep an eye out for it.

ronwood: Your skills as a program could come in mighty handy if we ever get this thing to that point and agian all help welcomed, desired and much appreciated.

8)Boy, Oh Boy I think were on our way.

Buzz-sawyer · « **Reply #33 on:** February 19, 2004, 10:45:55 am »

Teacher
It was pure simplicity...a common desktop computer with a 200 processor...in other words the computers you saw in the dumpster....
on the screen we viewed a shematic of the plant cylinders , motors shakers , temp. control....on screen were virtual slide adjusters and type in variables.
So there was plenty of computing power for this application....the signals were sent to the components of the system (say a on off solenoid) so via electronic messages sent by the computer the elements are run from a booth....VERY simple and compatible with what we are looking at here...the programs are very simple and I know someone who wrote one for home power generation controls....I have always though this would be a good approach

Jason_WI · « **Reply #34 on:** February 19, 2004, 11:42:25 am »

And then your PC crashes and your heating relay is stuck on because if the crash...........

Better have plan B or a fire extinguisher.

Jason

Den Socling · « **Reply #35 on:** February 19, 2004, 01:23:09 pm »

I think you should consider the way we do computer interface. Most loop controllers can have an RS485 interface connection. RS232 can be converted to RS485. Your computer already has RS232. That's the serial port.

If you use a loop controller with a computer interface, the computer can do data logging, historical graphs, etc. It will also give you remote access with pcAnywhere. I can connect to kilns on the other side of the Earth. But, if the computer goes down, nothing happens. The loop controllers keep going.

Man-machine-interface software can be mighty expensive. We can pay $600 to $5000 depending on how many addresses. We use WonderWare.

New loop controllers come with their own MMI software and it is free. But it's not as sophisticated as WonderWare.

shopteacher · « **Reply #36 on:** February 19, 2004, 03:07:24 pm »

Well guys, I'm game for what ever will work and be reliable. As I said earlier, electronics is not my bag so the simpler and easier to understand the better.
Can someone sketch out a schematic? Looking at the different components and their wiring would help me get a better idea of what the electrical system would look like and how it would operate.
I hope we can get a working example of one of these kilns. I think a lot of us small mill operators would really benefit from having this equipment available.
Den, believe me when I say I wish I could just give you a call and tell you to deliver one of your kilns tomorrow. Up to present the mill has just been for my own use and pleasure and doesn't bring in any revenue. As I get better situated and closer to retirement I would like to turn it into a subsidy for the pension.

Den Socling · « **Reply #37 on:** February 19, 2004, 04:41:03 pm »

Shopteacher,
I understand. It's just too bad that I have to make my experience available to our competitors. When too many outsiders were reading the information at our forum, we decided to make people register. Jeff can't limit members so I'll just bite the bullet.
Den

VA-Sawyer · « **Reply #38 on:** February 19, 2004, 06:56:34 pm »

A few years back I worked for a company called Kreuter Engineering Inc. They designed a Digital Control System for HVAC. They had big boards with 32 inputs and 32 outputs, smaller board with 8 inputs and 8 outputs and a small 4 X 4. I had 3 of the 8 X 8's hooked into my house when I lived in Indiana. I could sit at my computer and check temps in 7 or 8 locations (attic, bedroom, shop, basement, return vent,outside air, etc. It controlled the home furnace and A/C. Controlled the attic fans, shop furnace, shop lights, etc. It also recorded a ton of data. I could tell you how many times the furnace kicked on over a given time. How many hours the fan had run this month, this week, this year. What the high and low temps were for each day for the last year, etc. I never touched the thermostats in the house or shop. All three units talked to each other, so I could do the programming and checking from one location. They were powered from 24V transformers, and you could get a little circuit that would power them off of 24 V DC. They were very easy to program.
Kreuter had a number of dealers in the U.S. and Canada. Check with some of the larger HVAC people in your area. The name of the system was KMD. That was for Kreuter Manufacturing Digital.
VA-Sawyer

oakiemac · « **Reply #39 on:** February 19, 2004, 07:23:07 pm »

I've read through all these posting and find it interesting, but too much like work! Where I work we have many large freeze dryers to dry pharmacuticals. I work on the RTD, PLc,t/c, and loop controllers every day. I have thought about bringing in some wood and sneaking it into a dryer

One comment I'd like to make is 1torr=1000milimeters of Mercury not 1mm as stated. Also you can do alot of the controls with relay logic (like the old days) this would be cheaper and easier than a PLC.

Oakie

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Author Topic: Vacuum Kiln (Read 18323 times)