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Home Made Kiln Controller


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#21 Joseph F

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Posted 07 August 2015 - 07:21 PM

There is nothing wrong with reinventing the wheel. The code above is nice, but if you dont understand it, then what do you do when you want to change something in your controller. You can't, and if you just blindly use it, then you can't contact someone to change it or to find help your stuck. That is why I often rebuild things that are already working, but instead of just using their code completely, I read their code, and build my own code that does similar things, but this way I understand what is happening.

 

I think your doing the right thing starting from the beginning HBP.



#22 High Bridge Pottery

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Posted 07 August 2015 - 08:08 PM

I'm having enough fun remote logging into the pi over the local network :D already broken it 10 times. Managed to comment out my user in some file and then still be logged in as that user unable to do anything  :blink: It kept asking me 'Who are you?'

 

I will be doing a lot of copying wheels, pasting wheels, hitting wheels with hammers. Breaking wheels, running wheels and troubleshooting wheels  B)

 

Do you write your own libraries? Only if you need to? I guess understanding of them is needed to write a good program. I suppose they are a program within a program.

wntgd.jpg


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#23 Bob Coyle

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Posted 07 August 2015 - 09:42 PM

The code is written in C. A pretty old and common language.  It was just a sample. I did not know what your level of understanding is. basically what it does is loop and  read a value (temp) from the chip and send it out the USB port to another program.

 

The other program looks at the temperature and either tells the Arduino to turn  on or shut off a relay depending on what the ramp temp should be at the time. The MAX library you need to run the data acquisition is available on the Arduino site. I gave you the link.

 

Since you are a beginner, Nothing is going to come easy. As I said before, the Arduino module is cheap and has tons of code and support. The development interface is free for the download and comes with lots of example plug and play code. Since the code is written in public domain "C" it is almost infinitely expandable. Using visual drop in code blocks like the LEGO code interface and others, might seem simpler to learn, but you are stuck with what capability they will provide. To really do what you want to do will take some real commitment at your level... like probably months.

 

Here is an ebay link to a cheap Arduino clone ...

 

http://www.ebay.com/...=item4d30261ba9

 

Here is a link to the MAX 31855...

 

http://www.ebay.com/...=item462087c183

 

Buy the clone, download the Arduino development environment and play around with it.



#24 Pieter Mostert

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Posted 08 August 2015 - 06:04 AM

Besides the issue of support, the impression I got was that the Arduino is less finicky than the Raspberry Pi. But I don't have personal experience with either of them, so don't take my word for it. I think Bob's suggestion is good, but since you've already started using the Raspberry Pi you might want to check out this site for a controller that runs on a Raspberry Pi. It's for a gas kiln, but you should be able to use the code (available on GitHub) to get the controller to read the temperature.



#25 High Bridge Pottery

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Posted 08 August 2015 - 06:38 AM

Oh nice, that looks like a sweet project, they are still using the standard type K chip which is interesting. I wonder why he never swapped it in the chip or designed a new one as it looks like he can do that.


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#26 Bob Coyle

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Posted 08 August 2015 - 12:40 PM

The k chip is cheap. I can't remember what the  other one S maybe. I think it uses platinum so it is real expensive. The K is good up to 1300C or around 2300 F.



#27 High Bridge Pottery

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Posted 12 August 2015 - 07:23 AM

I seem to have been confused when looking at some specs, got an old thermocouple from a kiln that I can use. Good to know the chip will read up to there.

 

MAX31855 breakout board arrived and was wired up in about 5 minutes with the python libraries installed, example program working. Seemed so easy to read the thermocouple. Followed the tutorial on the Adafruit website.

 

Started looking into ways to log the temperature, got a bit lost in google drive trying to make their python libraries work so I could write the data to a google sheet. Never managed to get that working so I am writing out a .CVS format file with all the data in. It should log the temperature every minute. Makes a text file called Log with the date and time it is when you start the log.

import time
import sys
import os

import Adafruit_GPIO.SPI as SPI
import Adafruit_MAX31855.MAX31855 as MAX31855

TIME = time.strftime("%Y-%m-%d-%H:%M:%S")

CLK = 25
CS = 24
DO = 18
sensor = MAX31855.MAX31855(CLK, CS, DO)

firingHours = 8
firingMin = firingHours*60

file = open("Log" + TIME + ".txt", "a" )
file.write("Reading,Temperature,Internal Temperature\n")

for i in range (0,firingMin):
	file.write("%d,"%i + "%.2f" %sensor.readTempC() + ",%.2f" %sensor.readInternalC() + "\n")
	time.sleep(60)
file.close()

Ran a few tests putting it next to a fan heater and managed to get some workable stuff out. Now I just need some work to fire in the kiln so I can test out the temperature logging. Seemed like the simplest project to start with.

 

Attached File  Snap 2015-08-12 at 13.13.52.png   330.22KB   3 downloads


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#28 Bob Coyle

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Posted 12 August 2015 - 10:23 AM

Congrads !

 

looks like you got some temperature logged OK. I am not sure what you logged. the temperature on the left of the graph only goes up to 25. The graph shows a max of around 34???

 

Do you understand what the code is doing, or did you just copy it and run it?



#29 High Bridge Pottery

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Posted 12 August 2015 - 11:18 AM

Yea it went to around 33-34degC when I put the thermocouple in front of the heater. I read quite a few tutorials about writing out text files. Could be a better way but this is what worked for me first. It seems simple to get the chip to work, just need sensor,readTempC() and spits out a reading. Will be good to test it on my kiln that has working thermocouple and controller to see how accurate it is.

 

Now I need to work out what to do with the temperature readings other than writing it to a file.  :unsure:  :mellow:


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#30 Joseph F

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Posted 12 August 2015 - 11:55 AM

Congrats your moving right along.

 

If I was you, the first thing I would do with the temperature readings is setup a fake kiln. Meaning that you want to record data increases to resemble your real kilns firing along side your fake kiln.

 

So say you fire 500/h to 2000F, just for arguments sake.

 

You would write something that records temp increase, and rate increases.

 

To do that you would setup some basic variables like:

 

currenttemp = # input from TC rasp pi

lasttemp = # input from TC rasp pi,write a small script that before currenttemp is overwrote, it saves the currenttemp integer information to this variable

rate = currenttemp - lasttemp  # this will give you the rate per how often you check this, so if you updated current temp every minute it would be rate per minute of change total. roughly. 

rateperhour = rate*60 #this would be rate times 60 rate checks, = 1 hour of rate checks, so if your increasing by 2F per minute, according to the last rate check, your current rate per hour would be, 120F/per hour.

 

setup a function that every hour, minute, or seconds even it records the rate, current temp, and rate per hour into an array. then you could look at that array and print out the results to see how accurate your TC is firing along with your other kiln's TC

 

just an idea of where i would go if I was at this point.

 

of course you could increase your effectiveness of everything by checking every second, then doing those maths. There is a lot of different things you could do, you could build segment variables, ramp variables etc. You could build an entire fake program, and run it along and have it fail if your TC doesn't work along with it and stuff. lots of fun things before you actually build a real control box and start pumping directions and volts into a kiln.

 

keep us updated@!



#31 Bob Coyle

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Posted 12 August 2015 - 01:35 PM

I'll go along with Grype, It is good to have a the theoretical ramp graph to compare the run to. it gets a little more complicated if you are using a multi step ramp with holds.



#32 ggoodman

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Posted 20 September 2015 - 09:13 PM

ever thought of using one of these? this guy built it for a reflow oven similar ramp soak step heating just diffrent temps.... from my research look like you can build difrent firing schedules then load them via the USB interface when you want to change the program.

 

 http://www.rocketscr...duct/ospid-kit/

 

this is the tree I am barking up.



#33 High Bridge Pottery

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Posted 21 September 2015 - 09:53 AM

Haven't had much time to spend on this project. Think I have seen that open source PID, will be looking into all their stuff at some point. Looks like a great price if it can do what you want it to.


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#34 ggoodman

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Posted 23 September 2015 - 07:35 PM

Ill be investigating a lot more in a couple weeks. Have  a friend who is a electricle engineer who writes a bunch of languages he thinks this could be a great option. as it is I am in my last three weeks of nursing school so that is occupying my time.



#35 curt

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Posted 27 September 2015 - 08:13 PM

I think you already have the S chip, but I would suggest the R chip instead if you can get it.  R type is standard for use at Cone 10 temps and offers the best compromise for accuracy and durability among the various thermocouple types for a potters working at stoneware temps.

 

Most of the high-temperature gear I have seen on offer on EBay is K type, and a lot of the specs for different bits say they will go to 1300.  However, when you actually get the stuff in your hands you can tell it will not last any time at all at 1300, ie in continuous use at that temperature. 

 

However, I am rebuilding an old top loader (tomorrow or sometime later), but have already procured a couple of those cheap PID controllers ($30 to $50), some kanthal wire (elements) and some solid state relays (surprisingly/ridiculously cheap compared to what my local kiln co. wanted to do for me), so I am interested in how you go. 

 

I would be particularly interested in seeing this kind of basic homemade set up to control gas kiln solenoids and (icing on the cake) an oxyprobe or similar device to monitor and control reduction. 

 

Love your style/willingness to strike out on your own!



#36 High Bridge Pottery

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Posted 27 September 2015 - 08:35 PM

This link was posted before but you might have missed it. Using one of these to control a gas kiln.

 

https://www.raspberr...d-pottery-kiln/

 

The breakout I bought came with a type K and I have an old electric kiln type K that I am using. I haven't been doing too much on this recently as more important things but I am just about to convert my old electric to gas so hopefully needs must and I will sort out a little project on the pi.


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#37 David Woodin

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Posted 01 October 2015 - 05:15 PM

Omega.com in the USA has a 2 input data logger that allows you to download the information to your computer and view or print out a graph of your firing.  It is HH306A Thermometer/Data  Logger and comes with a disc to download what you need.

David



#38 RoriIltis

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Posted 16 October 2015 - 02:19 AM

I am working on my project and also i spent quite a bit of time researching DIY controllers earlier this year after my kiln's controller died.

Once I was heading towards using an Arduino Uno with the MAX31855K chip, but I ended up just getting a PID ramp/soak controller from Auber Instruments. 

I didn't want to have deal with trouble-shooting any issues that might occur, and the Auber controller wasn't that much more expensive.

But programming a controller would have been fun.



#39 Tim T

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Posted 18 October 2015 - 10:24 AM

Joel,

A couple of us down near Winchester have been talking about doing something similar - in my day job I do a lot of computer development, and currently have a project where we're using Arduinos (as they have more interfacing capabilities than the Pi). The thinking is:

- an Arduino for the sensors and a Pi or Intel board for the user interface

- better recording of temperature, voltage and current during the whole firing cycle

- prompts for manual tasks e.g. bungs in and out at set times or temperatures

- alarms for power cut, firing deviating too much from the plan, over firing or taking too long etc

- more intuitive and precise setting of the whole firing cycle, e.g. a modern consumer style user interface, and a controller that learns the max firing rate and the cooling rate of the kiln

- a touch screen for setting up the system and also showing what is hapening

- ability to log in remotely over WiFi or a wired network, so you can monitor things whilst ding other tasks

- for the gas kiln guys, eventually have servos controlling the gas flow and damper, plus interfacing to an oxygen meter

 

Unfortunately the day job is taking up too much time at the moment, and I need to get pots out for the Christmas shows etc, so the project is taking a back seat until the new year.

 

The day job project has International Paints/Akzo Nobel from Newcastle as one of its main partners, so I'll probably be going up your way in the coming year. We could meet for a beer and bounce some ideas around.



#40 Bob Coyle

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Posted 18 October 2015 - 02:33 PM

Hi Tim

 

I have started to write an app in java for a kiln controller. I previously wrote one in VB 6 but it is now obsolete so I am starting over again. The app communicates with the arduino through the com port and receives temperature data and send control signals to turn a solid state switch on and off. It has some fail safe logic built in and allows multi ramp input.  I tried to send a zip file with the code, but It was not allowed. but if you are interested contact me directly and I will send it to you ( or anyone else who is interested)

 

Bob Coyle






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