Tuesday, September 13, 2016

Converting Manual Gare Kiln to PID Controller Programmable Kiln

Difficulty Level (Easy, Medium, Hard, Insane):

For some reason I started thinking about getting a kiln a few months ago. Maybe it was because I could start doing any of the following:

1.       Cast my own telescope mirror blanks
2.       Use the lost-wax casting methods
3.       Fire my own pottery
4.       Cool down cast iron parts after welding/brazing

In any case, I saw a kiln on kijiji but they wanted over $600 bucks for it so I forgot about it and went on vacation. A few weeks later I just happened to search kijiji for a kiln and that same kiln (so I thought) was back for sale for $60 bucks saying it would need new heating elements. Naturally, I figured that the original sale didn’t go through because maybe a potential buyer noticed that the heating elements weren’t working.

I called the guy and told him I’d take it but when I showed up I realized that the first ad was a different kiln that had a programmable thermostat wheras this one was a manual on/off kiln. Not wanting to pass up the chance at getting a good deal I bought the kiln (he gave it to me for $50 bucks) and took it home.

The first thing I did was building a metal dolly I could set the kiln on for easy transport and to keep it off the ground as it does get quite hot when firing. I used my Metal Band Saw to cut up some ¾” by ¾” square metal tubing at the proper angle and welded it together in the octagonal shape of the kiln. Then, instead of buying four 3” casters for $5 bucks each, I spent $10 more and bought 3 snow mobile dollies on sale at Princess Auto, EACH having four 3” casters. I kept two of the three dollies for future use and cut one of them up and welded the dollies to the previously built octagonal frame.

After some research I found that the heating elements were only a few bucks each. Although I only needed 5 I ordered 10 just in case and for future use and – with the help of my brother in law – installed them in the kiln.

Then, I did some searching on ebay and found a programmable PID controller with 50 ramp/soak segments as well as two 50A, 200V rated Solid State Relays (SSR) to controll the on/off function of the heating elements.

Once I got the parts I noticed that the PID controller was a little bit too big to fit into the existing box on the kiln so I had to either pay someone to bend up a bigger one for me or build my own metal brake. Since I’ve always wanted to build/have a metal brake I made that my next project.

As soon as I finished the metal brake, I bent up some 20 gauge galvanized sheet metal I had lying around from another project, cut the holes for the PID controller, the indicator lamp, the main power line and the SSR controllers, put it all together, hooked it up to the newly installed heating elements and fired it up.

Learning how to program the PID controller took a bit of time, but now that I understand all the new terminology (see the full PID controller manual scanned below) it’s actually not as difficult as it seemed at first and, I have to say, the capability of that PID controller is phenomenal.

So now that it’s all done, I just need to find a project I can use it on!


The kiln in all its glory
Another view
The broken heating elements
Missing clamps on the lid rim
Rusted handle
Melted plastic on the side
Another view
The old wiring
Wiring to the 5 manual switches
Another view
The kiln sitter timing mechanism
Another view
Starting to take things apart
Cutting up the angles for the base
Another view
Lining up the pieces that will make the frame of the base
Another view
Tack-welded frame
At first I was going to cut up some 1/16" metal but decided against it
The dolly I scavenged for the casters
The finished metal base on wheels
Closer view

The bare case where all the electronics were housed
The newly bent housing
Wiring the new elements
Starting the electronics installation
Another angle 
The 50A, 220V rated Solid State Relay (SSR) mounted on some 1/4" aluminum
Close-up of the SSR
Installing the SSRs
Another view
The K-Type thermocouple encased with the old kiln sitter portion
The K-Type thermocouple installed on the kiln
Another view
Wiring up the SSRs
Another view
Getting things tidied up
View of the inside
Close-up of the inside
Another view
Using my DIY metal brake
Another view
The air-vent pieces installed
Close-up of the bottom
The PID controller installed and working
The electronics installed and mounted on the kiln
The kiln on the movable casters
The kiln in action
Close-up of the heating coils
Close-up of the make and model
PID controller diagram
PID controller make and model
An example of the type of PID controller I got

PID controller instructions Page 1 of 6

PID controller instructions Page 2 of 6

PID controller instructions Page 3 of 6

PID controller instructions Page 4 of 6

PID controller instructions Page 5 of 6

PID controller instructions Page 6 of 6
The SSR modules I got from ebay
The type of heating coil/resistance wire I got from ebay

DIY sheet metal brake
Metal band saw
MIG welder with MIG welder cart
Propane burner
Angle grinder with diamond cutting blade
Drill press
Sheet metal shears
Rivet tool
Measuring tape
Markers, pencil, grease pencil
Needle nose pliers
Step drill bit
Regular drill bits
Air compressor
Hook tool

Manual kiln - $50
Five kiln furnace heating elements (resistance wire, 220V, 1500W) - $19.29
Two 50A 250V SSR-50 DA Solid State Relay Modules (SSR) - $12.78
Two DIY SSR heat sinks
One programmable PID Controller with 50 Ramp Soak Segments (PID-RS-S-48) - $100.30
Two large marretts - $3.50
10' of 12-2 wire - $2.50
16" by 24" piece of 20 gage galvanized sheet metal - $7.00
Three drawer handles - $10.00
Two 2" stainless steel hose clamps - $2.00
One snowmobile dolly, cut apart for 4 casters $15.00
Rivets - $2.00
50A male plug - $15.00
One K-Type Thermocouple - $3.47


10 hrs

About $750

The 7500W sure put out some heat!!!


Bongodrummer said...

Cool. So could you/ will you also use it to melt aluminium for casting instead of the propane one?
Nice stuff.

Chris Eigenheer said...

@Bongodrummer, I'm not sure. The propane burner is really fast and I'm not sure if the kiln could keep up with it. Maybe If i had a really big cast that would require more than the 15lbs capacity of my crucible...

Unknown said...

I loved seeing this project blog. I'm doing almost exactly the same thing with an old ceramic kiln, converting it for glass fusing/slumping. My wife does glass work. I'm having trouble understanding how to program the PID controller (I believe it is the same controller you used). Could you offer some help to me? If so would you email me at bigandtall321@yahoo.com. Thanks and great job on your project

Anonymous said...

Thank you for a great posting of your kiln control conversion project. I am in the process of converting a similar model, the Gare 1818, to PID control. So far, I plan to use picoReflow on a RPi B+. Nice job on the wiring, too; that is my next task, cleaning out and checking connections on the four elements, wiring SSR and the mains supply. I may keep the Sitter in operation as a failsafe - maybe! Thanks again.
Best regards,

Unknown said...

like your enthusiasm and getting things done, will look up your telescope mirror project. Just so's everyone looking is aware - the ebay SSR's are nearly all counterfeit, the internals will not take the rated current! Also, the black tape over your mains wires on the SSR's is not a good thing. Big heat shrink tube possibly. You really need mica/fireproof insulation sheet around the mains terminals area. So the condition of the connections/cables is always visible. What you have done works, but let everyone know it is not necessarily 'the safest manufacturers/safety standards method'...

Randy Kaltenbach said...

What a blast! I'm just sourcing parts for nearly exactly this project!

I spent $50 for a 55gal drum dolly from Princess Auto to support my kiln and it seems to be right for the job.

Three questions:
Did you simply run the controller off of 240V from your supply?
Did you fuse the controller power input lines?
How have the controller and SSRs hold up with use?


Chris Eigenheer said...

@Unknown above, Yes, I run the controller off the 240V. No, I did not fuse the input lines. Lastly, I haven't used it all that much but so far it's been working well.

Mike in San Diego said...

Great project, and cost savings! I've recently built a similar PID controller and kiln dolly for my wife's 6,000 watt large hobby kiln. The cheap Chinese PID controller has autotune, which helps achieve and maintain the temperature even under venting conditions, a tough task with large thermal mass. I'm upgrading to a ramp soak PID controller which is better for ceramics where you program multiple steps of several temps and heating rates during every firing.
Be sure to use only 900F rated wire with teflon/fiberglass/nomex heat wrap on cables that run to heating coils, and you should install a cooling fan in the controls box because the kiln makes the PID and SSRs overheat when the kiln is at higher temps. I know because I measured the temps (>130F) at the SSR. Use high temp rated nickel over steel connectors when connecting to the heating elements, regular ring lugs can't take the heat.

Anonymous said...

Can you tell me where I might find a owners book on a GARE 1822 for wiring. I have an old kiln where the wires have been replace and no color coding. Im not an electrician but can follow instructions. Thank

Clare B said...

Nice blog you have

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