Heating things up is one of the most performed tasks in a lab. Quite a lot of times it is not enough to simply hold something at a certain temperature, but the rate at which something is heated and for how long is just as important. Especially when you try to develop catalysts for chemical processes, the temperature program and exact temperature control is crucial and you probably do not want to stay in the lab for 16 hours to manually adapt your temperature program. Unfortunately, programmable temperature controllers that can automate processes are really expensive. So I decided to build a highly customizable controller that is able to run temperature ramps and read multiple different temperature programs from a SD card. It also provides a logging function on the SD card that allows you to evaluate the resulting temperature profile after running a program.

It is a great hack for your heating devices, since it can be easily connected to almost any heating apparatus you can think of, as long as it allows you to also connect a thermocouple. So If you have ever thought about building the perfect electric kiln (there are multiple really good explanations online) or hot plate (take a look at the steps 6 and 7), now is your time.

Overall the controller should cost you about $45 and the hot plate about $55. You should easily be able to build this as a weekend project.

Step 1: Things you need

Programmable temperature controller:

  • Solid state relays (5V control voltage, 16 A load current)
  • LCD (e.g. on amazon.com)
  • SD card board
  • MAX 6675 controller board (e.g. on olimex.com)
  • Atmega 328 chip & socket
  • 5 x 10 kΩ Resistors
  • 4 x 1 kΩ Resistors
  • 4 x 560 Ω Resistors
  • 1 µF Capacitor
  • 100 pF Capacitor
  • 2 x 22pF Capacitor
  • 16 MHz quartz oscillator
  • LM7805 5V linear voltage regulator
  • Rotary encoder
  • Mechanical 110 V switches
  • 10 A fuse and fuse holder
For the casing:
  • 4 mm ply wood
  • Wood glue
  • Laser cutter
  • Primer
  • Paint

Hot plate:

  • Metal case as support (e.g. an old computer power supply)
  • Small plastic case
  • Aluminum plate 20x20x1 cm
  • 2 Cartridge Heaters (1/4’’ or 6 mm) (e.g. on amazon.com or from China on ebay.com)
  • Type K thermocouple (1/4’’ or 6 mm)
  • Steel thread rod (¼ ‘’ or 3/8’’) and nuts
  • Locking screws
  • Lead
  • Copper paste
  • Long (ca. 30 cm) drill for the heating cartridge and thermocouple
  • Tap & die for Locking screw and steel thread rod
  • Drill press
<p>Great project. Thanks for sharing. Ever thought about extending this to a heating AND cooling plate using TEC? </p>
not sure if I missed it, does the heater have feedback correction?
<p>Hi, I'm looking to do something quite similar to this using a cartridge heater, thermocouple and an Uno to control the temperature of an aluminium cylinder. My original intention was to earth the cylinder as it will be an exposed piece of metal (with a mains cartridge heater inside it), but I have just discovered that touching my thermocouple to the earthed metal produces a temperature reading of 0. Did you use an electrically isolated thermocouple? I'm struggling to find one with the right body type in the UK. Thanks</p>
<p>Hi can I modify an analog hot plate that I would buy from the store with this instructable? </p>
<p>Wow, your projects are so well built... I love all of them.</p><p>For this one you could also use a commercial PID controller (<a href="http://www.ebay.com/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0&_nkw=rex%20c-100&_sacat=0&_from=R40" rel="nofollow">digital temperature controllers</a> on eBay), btw your design is much more unique!</p>
<p>Hi, yes you can, but they are not programmable and therefore pretty useless in chemical engineering. </p>
<p>YOU WON A MILL!! Congrats! Again :-)</p><p>Y.</p>
<p>Thank you! *happy dance*. Greetings from Matthias (I still couldn't convince him to write his first instructable...)</p>
<p>High five, BrittLiv!!!</p>
<p>Thank you! Any plans for your hundred instructable yet?</p>
Hey Britt! <br><br>Lot's of plans, but they have to wait. I cannot find the battery charger for my camera! <br><br>No mail service here in the Baja boondocks, so I'll need to buy another one when I visit the States again. I'm just in no hurry to leave this warm and sunny paradise. :-D<br><br>Thanks for asking! Congrats again!!!!
<p>congratulations </p>
<p>Thank you!</p>
Congratulations,being a girl,you are more awesome than we boys :)
<p>Haha, thanks! Good luck in the hardware hacking contest. </p>
<p>Britt,i have sent u a friend request on facebook,accept if u don't mind or just ignore it!!<br>Thanks<br>A big fan of yours!!</p>
<p>Hi, I just did. My facebook account is quite boring, though since I don't post much stuff.</p>
<p>Oh,but atleast i will be connected!!</p>
<p>Congratulations on winning the Grand Prize Britt. Your temperature profile controller would be an excellent addition to my &quot;Melt-o-matic&quot; digital melting point apparatus, allowing automated melting point determinations. I wish I knew how to write program code like yours, but I'm just an old chemist from the pre-computer dark ages.</p>
<p>Thank you! Congrats on your win, too. I am impressed how you use mainly cheap or recycled materials.</p>
<p>Good job congrats on the win :) </p>
<p>Thank you *happy dance*</p>
hi, congratulations on winning the Grand Prize in Build My Lab Contest... mine got the Judges' Prize: Build Their Lab
Congratulations to you, too! I am sure you will put the 3D printer to a good use.
I have a programmable hotplate that I need to refurbish at some point. If I can't get its existing controller to work well, I'll probably use yours. (I got it out of the electronics recycling; I don't know if it works at all!)
Man i dont have time/patience/knoledge to do this project but i need this tool so my question is,could you make it for me and send to TN? <br>Please let me know. fb.com/henrique.h12 or whatsapp +59160780320
Hi, I am glad that it is helpful. Sadly I don't have the time to build an other one. I hope you can find somebody else.
Inspiring, legit !!
At the start of the read I wanted to say PID control, then utilize auto learning , You are using PID and are considering the latter. Kudos to you. <br> <br>PID is required and auto learning is great. But both features are dependent on the heat load. So several heating profiles will be required. <br> <br>On the other hand, I am not very happy with the plates temperature profile. More cartridges are needed. I don't know if there are variable wattage cartridge heaters in th\is size range. I've used that feature in say 5/8&quot; X 24&quot; heaters to help create a more uniform temp. profile in rubber molding platens. Have you considered heat mats? They could help in heat distribution. <br> <br>Again, I am still impressed with your prototype design.
Thank you! 4 cartridge heaters are not going to change as much as you might hope. I have uploaded another simulation and since you could be interested one after applying insulation. <br>In my case two are really enough, since I doubt, that I will ever heat something of exactly the same size as the the plate. <br>I didn't know that heat mats can provide such high temperatures, I will definitely have a look into that.
there is another way to save the program steps. I use one line of text as in : <br> <br>6,300,130,60,780,600,60,1,700,140,1,510,90,600,400,20,900,20,0 <br>With no maximum to the number of steps <br> <br>The first number is the number of steps, the rest is in blocks of 3, the rate, Temperature and rest-time. With a function I read these values int an array. <br> <br>I could upload the code and a picture , but apparently I don't know how to :( <br> <br>
Thanks, but the step limit is actually given by the array-space I allocate in the Atmega. When running a program I want to load the whole program into the RAM so you can remove the SD card without canceling your run
Dear BrittLiv, how can I upload a pdf and ino file as comment? I'm new to Instructables, and don't know how to <br>Pushing the button add Images and select files seems not to be enough :(
Hi, thanks a lot for your effort! As far as I know you can't add ino files to instructables.<br> That's why I used a text box. Since you are a pro member, just click on &quot;Rich Editor&quot; then &quot;Source&quot; and add one like this:<br> &lt;pre&gt;&lt;textarea cols=&quot;75&quot; name=&quot;code&quot; readonly=&quot;&quot; rows=&quot;20&quot; style=&quot;width: 600.0px;height: 294.0px;&quot;&gt;<strong>your code</strong> &lt;/textarea&gt;&lt;/pre&gt;<br> <br> About the pdf I am not sure whether you can add it to comments. Can you maybe upload it somewhere else (e.g. dropbox) and share a link?<br> <br> The simplest solution to the space problem is probably to get a second Atmega connect it with the IC2 interface and to split all the tasks. Especially since the SC-Card library literally eats up your space (~16 kByte) and the spare amount of free SRAM (apparently only a few bytes are left, as initializing new variables kills the program) might interfere with most of the more sophisticated approaches.
I don't know why but now the selecting of files worked<br><br>You will find my .ino file, a pdf with the result ( in Dutch but the graph is International :)), a photo of the oven and control and last but not least a curve file.<br><br>By the way it is a setup to heat glass , to shape and fuse<br><br>regards, Harrie
Wow, great job! Thanks for sharing your code! I will definitely take a look at it.
I haven't checked your code (sorry) but have you thought about quantizing your temperature so it is only specified in steps of 5 for example. This way you can use a uint8_t (i.e. unsigned char). Doing this with all the data you might want to use a C bit-field (http://en.wikipedia.org/wiki/Bit_field) <br> <br>You may also could reduce the memory usage further with a basic zip/delta compression. A simple approach you store the delta/change (+-128) between steps so that each value can be stored as a int8_t (i.e. signed char) . This incurs a slight increase in complexity and requires extra steps for large step changes. There are many ways you could take this further including RLE encoding and a 3bits step header which determines what has changed between steps. Complexity of the code goes up a significantly there though so would probably never be worth the effort! <br>
You couldn't check as I didn't upload it so far. If you could tell me how to upload files, You could see what the code is doing, and...how &quot;good&quot; the wanted curve is followed :)
Wow - very impressed with the 328 coding in this project! i will have to read through it carefully again to really lean the most from this one!!
Awesome writeup! <br> <br>The autotunig library you mentioned would be to fine tune the PID parameters and help prevent the slight overshoot of the initial temperature ramp? <br> <br>What software did you use for the temperature simulations?
Hi, thank you!&nbsp; The autotuning library automatically determines tuning constants. You can find out more about it <a href="http://brettbeauregard.com/blog/2012/01/arduino-pid-autotune-library/" rel="nofollow">here</a>.<br> I used COMSOL Multiphysics.
Great! Thanks for the reply (and link)!
Your instructables are always amazing and professional!!! Fantastic Work!!! <br> <br>PS... Voted :)
Thank you! Getting feedback like yours motivates me a lot!
I could use more description of the 'heating cartridges'. I am not immediately familiar with the type shown. Where would I expect to find these?
Hi, you can get them for example on <a href="http://www.amazon.com/gp/product/B00DN6BS7M/ref=as_li_ss_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B00DN6BS7M&linkCode=as2&tag=myinstrucacco-20" rel="nofollow">amazon.com</a><img alt="" border="0" class="khqcimfhgftyiqspqgwj" height="1" src="http://ir-na.amazon-adsystem.com/e/ir?t=myinstrucacco-20&l=as2&o=1&a=B00DN6BS7M" style="border: none;margin: 0.0px;" width="1"> or from China on <a href="http://www.ebay.de/itm/6mm-x-100mm-110V-300W-Watt-Power-Cartridge-Heater-Heating-Element-/330978162738?pt=AU_Business_Industrial_Industrial_Supply_MRO&hash=item4d0fd5f832" rel="nofollow">ebay.com</a>. Thanks for bringing that to my attention, I have added a link to the parts list.
Great instructable. I could use it for my heat treating furnace, if and when I get the time to build it. Voted for you!
Thank you! I would love to see some pictures, should you finish it.
good for the &quot;caution advice&quot; (Murphy's law: &quot;a hot surface its exactly like a cold surface&quot;)
Wow... Very impressive detail in this Instructable. I've been wanting to learn laser cutting and PCB etching, and this is an impressive practical application. Well done.

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Bio: Hi, my name is Britt Michelsen, I'm a Chemical Engineer especially interested in Computational Fluid Dynamics. To balance all the theoretical work I like ... More »
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